International Symposium on Room Acoustics
ISRA 2007 SEVILLA
 
Seville, 10 - 12 September 2007
 
Satellite Symposium of the 19th International Congress on Acoustics

S01

The acoustical improvement of historic monuments: Saint Joseph chapel – a case-study

PACS: 43.55.Gx

Schmich, Isabelle¹; Bruder, Pierre²

¹Centre Scientifique et Technique du Bâtiment; 22, rue Joseph Fourier, 38400 St Martin d'Hères, France; isabelle.schmich_at_or_arroba_cstb.fr
²Centre Scientifique et Technique du Bâtiment, retired

The Saint Joseph chapel in the city of Caluire et Cuire, France is an historic monument built in 1885 by the architect Sainte Marie Perrin. CSTB has been asked to study the acoustics of the chapel. The aim is to create an acoustic environment that permits non-amplified performances such as chamber music with the goal of a reverberation time of 1.5 s. Characterizing acoustic measurements have been done in the chapel. The measurement results are presented. They show a reverberant acoustic which is too high for classical music. After analysis of the acoustic measurements, CSTB was asked to propose modifications to improve the acoustics. These proposed modifications have to take into account the constraints due to the historical shape and architecture of the chapel. Two different solutions are proposed. The first solution is based on greatly increasing the absorbing surfaces and comes close to the ideal acoustic for classical music. The second solution allows the improvement of the actual acoustic with less absorbing material. Some diffuse and mode breaking surfaces are added. This second solution also includes a proposal for adapted music in this architectural and acoustical framework.

PACS: 43.55.Cs

Westbrandt, Anders; Gustafsson, Jan-Inge

Akustikon AB, Baldersgatan 4 , 411 02 Gothenburg; Sweden. anders_at_or_arroba_akustikon.se; jan-inge_at_or_arroba_akustikon.se

The desired room acoustical properties in studios for speech reproduction and their control rooms have been well investigated during the last fifty years. In contemporary radio broadcast though the trend is to build multi functional studios that can be used both as a studio with adjacent control room but also as a studio/control room with the programme presenter also functioning as engineer. Existing studios has been acoustically measured and a listening tests has been constructed to suggest room properties that can produce good acoustics both for critical listening in loudspeakers and speech pick up. In the listening tests an expert jury of sound technicians has been used to judge the control room aspects of the problem and a non-expert jury for the speech studio aspects. Acoustical criterion and physical properties of the “preferred” -and “not preferred”- room will be presented and compared.

PACS: 43.20.El

Tu Mingchiu

College of Architecture and Urban Planning, Tongji University, Shanghai, China, tuming85_at_or_arroba_126.com

Lighting and stage facilities in concert hall are not as complicated as opera house, but the acoustics quality is most the crucial among all kinds of hall design which can not be evaluated with single acoustical parameter. Acoustical design usually presents an overall effect only. Difficult to predict the result of acoustical design in combining many acoustical parameters. Here suggests criterion method by the area coefficient counted with multi-dimension rose graph, each dimension in the graph denoting an individual acoustic parameter, as the technique rule of the combined acoustical criterion. Therefore area has shown in the rose graph needs to more larger and be better for acoustics in the hall. Measurement of the concert hall usually takes with international standard (ISO 3382) processing the minimum test points by scale. It just take account of few selected positions only. Now through digital simulation predict the acoustics parameters even at every seat position. And can get the percentage of the optimum positions as criteria of acoustics. From there statistical data, not only can make compares with different acoustical design, and also know how to improve the acoustical design. This method has been used to optimize a medium-size hall project design from five different ceiling configurations.

PACS: 43.55.Cs

Tor Halmrast

^a Statsbygg (Norwegian Directorate of Public Construction and Property) tor.halmrast_at_or_arroba_statsbvaa.no
^b University of Oslo, Dept. of Musicology, Ass. Professor.

The paper gives information and measurements of the acoustics of an outdoor theatre in a quarry in Fjaereheia, Grimstad, in the southern part of Norway. The site is well known for its natural acoustics. The reason for the good acoustics is not an "arkeztra" platform like the old greek amphi-theatres, but massive stonewalls at the rear of the huge "stage". This theatre gives the actors the possibility of adjusting the voice and the direction of head in a very elegant manner, and use echoes as an effect in the performance. The acoustic measurements indicate that one should not use omni-directional loudspeakers when measuring details of such theatre acoustics.

PACS: 43.20.El

Vercammen, Martijn

Peutz bv, P.O. Box 66, NL–6585 ZH MOOK, Netherlands; m.vercammen_at_or_arroba_mook.peutz.nl

Many small or large rooms have concave surfaces. With improved building technology and fashions in architecture (blobs) problems due to these surfaces are encountered more and more. Some situations are described in literature [1,2,3]. In our consultancy work we had to deal with these situations e.g. in concert halls [4,5]. When sound is reflected from a concave surfaces the geometry of the surface will force the energy to concentrate. The sound pressure due to this focussing if mostly calculated by computer simulation techniques applied on a segmented shape or by a geometrical approximation. Both methods however fail in the focussing point, the result is not even close to the real value. To correctly estimate the sound pressure a wave extrapolation method is used, that will be presented here.

PACS: 43,25.Vt

Nash, Antony

Charles M. Salter Associates, 130 Sutter Street, Suite 500, San Francisco, California 94104 USA; anthony.nash_at_or_arroba_cmsalter.com

When measuring the acoustical properties of large rooms, we know from experience that an inflated balloon can be an effective and consistent sound source in the far field. Aside from some data presented by Watters and Griesinger, there is very little documentation in the literature regarding the near-field sound pressure spectrum or the directional characteristics of this common acoustical source. The present paper describes some experimental measurements of balloons exploded both in a large room and also in a free sound field. In the free-field case, the sound pressures at one meter were measured by an array of microphones distributed over the balloon's surface. The data from the microphones were recorded on a multi-channel tape machine along with a synchronizing signal from an electrical detonator. The internal pressure and size of each inflated balloon was controlled prior to detonation. We found that the repeatability of the near field sound pressures (in 1/3 octave bands) was within two decibels above 100 hertz.

PACS: 43.55.Br

Rossell, Ivana; Artís, Pere

Enginyeria i Arquitectura La Salle, Universitat Ramon Llull Quatre Camins 2, 08022 Barcelona, Spain; ivana_at_or_arroba_salle.url.edu; pereag_at_or_arroba_salle.url.edu.

Sabine and Eyring equations are based on the diffuse field theory. However, most cases in real rooms present a non-diffuse sound field. This paper addresses an analytical comparison of classical equations to “non-diffuse field” equations, such as Fitzroy's, Arau's or the European Standard EN 12354 part 6 from Nilsson's theory. I out study the influence of the room shape and the absorption distribution in the room are considered. Also scattering effect is taken into account in some cases. According to these considerations, Arau's and Nilsson's model accuracy seems to supersede one to the other depending on the room shape and absorption distribution.

PACS: 43.55 Gx, 43.55 Ka

Cappello, Diego¹; Prodi, Nicola² ; Pompoli, Roberto²

¹Facoltà di Ingegneria, Università di Trento, Italy;
²Dipartimento di Ingegneria, Università di Ferrara, Italy; nicola.prodi_at_or_arroba_unife.it

Due to the massive use of technological resources, the management of the stagehouse in an opera house has become a more and more sophisticated issue during the years. Currently new fly towers are designed to host several stage settings simultaneously thanks to a consistent increase of volume. The same trend can be verified also in the case of restorations, and the most important consequence is the substantial change in the traditional ratio of volumes between the main hall and the stagehouse. Since the system can be actually regarded as an coupled one, a potential threaten might result for the hall acoustics. In this work a case history covering the above issues is presented in the case of an historical opera house, the Zandonai Theatre in Rovereto, Italy. In the first place acoustical measurements were done with the aim of capturing the acoustical coupling of the two volumes. Then statistical and computer models were prepared and tuned upon measurement results. By doing so the alterations induced on the sound field by the new and bigger fly tower could be predicted with good precision. In the work the whole process is described and the suitability of the above numerical methods is discussed.

PACS: 43.55.Cs

J. Sarwono.¹; A. Emil.¹;W.S. Subowo²; H. Onggo²

¹Department of Engineering Physics – ITB.; Jl. Ganesa 10, Bandung 40132, Indonesia; jsarwono_at_or_arroba_tf.itb.ac.id
²Research Center for Physics, Indonesian Institute of Sciences, Bandung 40132, Indonesia;

Kapok fibre has a good acoustic properties, i.e. the random coefficient absorption is comparable to glass wool with the same density and thickness. The kapok fibre sound absorber modules have been made and applied in a real auditorium, at the first floor of LIPI building No.10, in Bandung, Indonesia. The acoustics performances of the auditorium room before and after application of sound absorber have been measured. The result shows that by covering 30% of its interior surfaces with kapok sound absorber combined with curtains on the glass door and windows, the clarity (C-80) and intelligibility (D-50) are increase by 300% and 200%, respectively, comparing to the untreatment condition. The treatment also reduced the reverberation time by 40%.

PACS: 43.55. Fw

Wei Lin.¹; Wei-Hwa Chiang²

Department of Architecture,National TaiwanUniversity of Science and Technology, #43, Sec.4, Keelung Rd., Taipei, Taiwan, Republic of China ¹Ph.D student, D9313001_at_or_arroba_mail.ntust.edu.tw; ²Professor, Edchiang1224_at_or_arroba_hotmail.com

The influence of source directivity can be significant for chamber music performances, particularly for arena type halls that have improved visual perception to create stronger feelings of intimacy with the audience. The aim of this study was to analyze the effect of source directivity in a recital hall with seats surrounding the stage platform. The effects of room form, source type and orientation, and surface treatment were evaluated based on acoustical simulations using CATT software that accounted for source directivity and surface treatments. The room volume was set to approximately 4000 m3. Most of the acoustical parameters derived from a baritone singer revealed only one factor that can be best represented by 2-k Hz early strength factor GE. Whilst the influence of length-to-width proportion on the distribution of 2-kHz GE from a front facing baritone singer was little, the acoustical energy behind a 45° turned singer was prominently reduced when the room width was increased from 17 m to 22.6 m. The problem could be resolved by limiting the width of the platform as well as splaying the side boxes towards the platform. The energy loss can be compensated for by placing a reflective surface 6-m in front of the platform and additional improvement can be achieved by changing the ceiling to pyramid shape.

PACS: 43.55.Cs

A. Simeon; J. Sarwono; FX. N. Soelami.

Department of Engineering Physics – ITB; Jl. Ganesa 10, Bandung 40132, Indonesia; jsarwono_at_or_arroba_tf.itb.ac.id

Church, a worship space for Christian, which is used as a room not only for speech, but also for music performance, is categorized as a multipurpose room that has to fulfil some specified conditions based on its function. GKI Taman Cibunut was chosen as the object of this research. Acoustics conditions of a worship space can be illustrated by acoustic parameters, such as SPL distribution, reverberation time (RT and EDT), clarity for music (C₈₀), clarity for speech (D₅₀), and RASTI. Acoustics condition for a room can be determined by several ways. One of them is by sound field measurement using binaural room impulse response (BRIR). This method is used by means of recording the impulse response of the room. By modelling and simulation, acoustics condition of the room can also be determined. In this research, the room used is GKI Taman Cibunut. The results of measurements show that in empty condition GKI Taman Cibunut has EDT value between 1.4 and 1.8 second. This value meets the optimum reverberation for multipurpose room. C₈₀ value meets standard criteria, while D₅₀ value in some point is below standard criteria. SPL distribution, C₈₀, D₅₀, RASTI at GKI Taman Cibunut can be reformed by applying diffuser and relocated loudspeaker position.

PACS: 43.55 Ka, 43.55 Mc

San Martín, Ricardo A; Aramendía, Emilio; Arana, Miguel

Acoustics Laboratory, Physics Department, Public University of Navarre; Campus de Arrosadía 31006, Pamplona, Spain; ricardo.sanmartin_at_or_arroba_unavarra.es.

The ability to predict room acoustical parameters by means of simulation software has been repeatedly demonstrated. Numerous studies compare the results obtained from simulations with the corresponding measurements. Taking a step further, the increasing computing power enables the acoustician to test a lot of variables quickly and cheaply, thus permitting configurations which would be unfeasible with the only help of measurement procedures. This is the case of the present work. The directivity of four different acoustic sources, all fulfilling the ISO 3382 requirements, was simulated and the influence of its accurate orientation spatially quantified. The results obtained for a well-known concert hall (the Swedish ELMIA hall tested in the 2nd Round Robin) will be presented. As recent studies have shown, directionality of the source has a significant influence, especially at high frequencies where measurement uncertainties could be greater than figures for the corresponding just noticeable differences –jnd's– at least for those parameters that are calculated with lower integration times.

PACS: 43.55.Cs

Nilsson, Erling¹; Andersson, Nils-Åke²

¹Saint-Gobain Ecophon AB, SE 260 61 Hyllinge, Sweden; erling.nilsson_at_or_arroba_ecophon.se
²Saint-Gobain Ecophon AB, SE 260 61 Hyllinge, Sweden; NilsAke.Andersson_at_or_arroba_ecophon.se

The aim of this paper is to describe the behaviour of sound field in rooms with absorbent ceiling treatment in respect to steady-state sound pressure levels (SPL) and sound decays. It is shown that the reverberation time and steady-state SPL’s are determined by different parts of the sound field and that they are weakly related to each other. As an example, two rooms with equal reverberation times can have significantly different influence on the steady-state SPL’s. This is in contradiction to the diffuse field theory. Measurement results from eight classrooms with different ceiling treatments are presented. Formulas for estimating the reverberation time and the decrease in SPL in rooms with ceiling treatment will be presented as well.

PACS: 43.55.Cs

Billon, Alexis

I LEPTAB Université de La Rochelle, Av. M. Crépeau 17042 La Rochelle, abillon_at_or_arroba_univ-lr.fr

In a system of coupled rooms, a double-sloped can be observed in the room containing the source when the coupled room is more reverberant. This decay is formed of a first quick energy decrease due to the first room and a second slower one due to the energy which is fed back from the coupled room. Today, this effect is used to obtain simultaneously clarity and reverberance in concert halls. Parameters to achieve a strong double-sloped decay are now well known. In this preliminary work, the spatial variation of the double decay strength within the concert hall is studied using numerical simulations. Firstly, the indicators quantifying the double decay used in this study are presented. Then, the results of two configurations with the same coupling characteristics but with different coupling area locations are compared. Finally, an empirical model based on the statistical theory is proposed.

PACS: 43.55.Fw , 43.55.Ka

Stephenson, Uwe M.

HafenCity Universität, Hamburg; Hebebrandstrasse 1, 22297 Hamburg, Germany; post_at_or_arroba_umstephenson.de

Room acoustical parameters as the sound pressure level decay, the Deutlichkeit (distinctness), the EDT are influenced mainly by the longitudinal section of an auditorium, especially its ceiling profile. But does also the reverberation time (with same volume and absorption area) depend on the ceiling profile? Has a (conical) tent-shaped hall as the 'Philharmonie' in Berlin or the new 'Elbphilharmonie' in Hamburg a smaller reverberation time than a shoe-box, or is always Sabine right? How does this depend on the 'roughness' respectively diffusivity of the surfaces? This mainly 2-dimensional problem has been investigated by a sound particle simulation (ray tracing) programme. It turns out that, if the surfaces are not totally diffusely scattering, there is a considerable influence of the ceiling profile on the reverberation time.

PACS: 43.55.Br

Delannoy, Jaime.

Universidad Tecnológica de Chile – Sede Pérez Rosales. Santiago, Chile; jdelannoy_at_or_arroba_utc.cl

This work compares two types of the design criteria for rectangular rooms. Several room proportions criterions (like Bolt, Sepmeyer and others) are used with different dimensions and faced with the Bonello´s criterion. The results obtained shows the ranges where different room proportions criteria and Bonello´s criterion are simultaneously fulfilled.

PACS: 43.55.Cs

Antunes, José¹; Inácio, Octávio²

¹Instituto Instituto Tecnológico Nuclear, Applied Dynamics Laboratory, Estrada Nacional 10, 2686 Sacavém, Portugal; jantunes_at_or_arroba_itn.pt.
²ESMAE–Instituto Politécnico do Porto, Musical Acoustics Laboratory, R. da Alegria 503, 4000–045 Porto, Portugal; OctavioInacio_at_or_arroba_esmae-ipp.pt.

Helmholtz resonators are often applied for the sound equalisation of control rooms in recording studios, through adequate levelling of the low frequency acoustic modal room responses. The number of controlled acoustic modes depends on the central frequency and damping of resonators, as well as on the modal density of the controlled system within the resonators frequency range. In a recent paper we proposed to improve the efficiency of such devices by, instead of using basic Helmholtz resonators develop shape optimized multi-modal resonators in order to cope with a larger number of intrusive room modes. In spite of the promising results thus obtained, further work is needed to demonstrate the feasibility of such approach. The present paper is a further step in that direction by analysing the acoustics of the fully coupled room/resonators system. More specifically, using a substructure computational approach we theoretically derive the coupled acoustical modes of control rooms fitted with several optimized multi-mode resonators.

PACS: 43.55 Fw

Lautenbach, Margriet; Heringa, Peter; Vercammen, Martijn

Peutz b. v. P.P. Box 696, NL–2700 AR Zoetermeer, Netherlands; m.lautenbach_at_or_arroba_zoetermeer.peutz.nl.

In the Netherlands there are quite a number of recently build, adjusted or to be developed buildings for large scale indoor pop events with a capacity of more than 5000 people. E.g. the Heineken Music Hall and the Music Dome are especially designed for pop music, the latter still in the process of design. Ahoy and The Amsterdam Arena are multi-purpose buildings, designed to accommodate a variety of large scale events. Designing large halls for indoor pop music is a room acoustic challenge. The music is reproduced through electro-acoustic systems; therefore a high direct-to-reverberation ratio is to be aimed at for good definition. Because of the large dimensions, the delay between direct sound en the first-order reflections is significant and reflections may be heard as echo´s if they´re too strong. A radical suppression of such reflections, also for low frequencies, is a necessity. Notwithstanding little reverberation, a homogeneous energy distribution is needed to realise sufficient loudness at any visitors´ place. In this paper problems and possible solutions to these aspects are discussed with reference to validation measurements of the Heineken Music Hall, the preliminary design of the Music Dome as well as to acoustic modifications in the Amsterdam Arena in favour of pop music.

PACS: 43.55.Fw

Möller, H; Ilomäki T; Auvinen J; Ruusuvuori A

Akukon Oy Consulting Engineers; Kornetintie 4 a, 00380 Helsink, Finland; henrik.moller_at_or_arroba_akukon.fi.

Hämeenlinna is a city of about 80000 inhabitants, approximately 100 km north of Helsinki. Traditionally the city is more know for its medieval castle and its ice hockey team than as a cultural city, but it does have a city theatre, music education facilities and a small city orchestra. The Verkatehdas complex is an old factory complex more or less in the city centre. The whole complex is redeveloped to hold different kinds of cultural related activities. In the first phase, described in this paper, includes the building of a new concert/multipurpose hall as well as a cinema multiplex. The second phase will include facilities for music education and general arts education. In the future, it is the plan that the city theatre will move to a refurbished hall in the complex. This paper describes the acoustic design of the Verkatehdas Hall in Hämeenlinna, Finland.

PACS: 43.55.Cs

Gade, Anders Christian

Acoustic Technology, Ørsted DTU, Technical University of Denmark; acg_at_or_arroba_oersted.dtu.dk and Gade & Mortensen Akustik, anders.gade_at_or_arroba_get2net.dk

In Copenhagen, Denmark, a new, large opera opened in 2005. For the opera company, which used to perform in a smaller theatre (The "Old Stage" of the Royal Theatre), this has given at least two challenges: 1) the singers are weaker as heard primarily by the singers themselves, and 2) and musicians playing in the pit feel an increased demand for playing louder in order to fill the larger auditorium volume with sound. These two challenges lead to two studies ordered by the Opera: one dealing with guide lines for the design of stage sets in order for them to contribute as much as possible to the support of the singers’ voices, and one investigating how the sound levels in the pit can be reduced without compromising the artistic quality of the performance. The latter is strongly related to implementation of the EU Directive 2003/10/EC "on the minimum health and safety requirements regarding the exposure of workers to the risks arising from physical agents (noise)", with which the music and entertainment sectors in all EU countries must comply after 15th February 2008.

PACS: 43.55.Fw

Albert Xu

XU–ACOUSTIQUE – 75003 Paris, France

Based on the experience of these two concert halls, this article would like to go beyond their excellent reputation with the public and the musicians to discuss their unresolved issues. The “Philharmonie de Luxembourg” is used mainly for the classic music with a large hall of 1500 seats with a concert pipe organ with 81 stops / 6738 pips (below, left) and a smaller chamber music hall of 304 seats (below, right). The architect Christian de Portzamparc was appointed in 1997 by international competition. This building was inaugurated at July 2005, with much enthusiasm and appreciation, even though there were discrepancies between the results of the calculation, simulation models and the in situ measurements in the occupied hall, for reasons such as the underestimation the low frequency absorption of the audience. The “Sala de Sinfoni” in the Centro Cultural Miguel Delibes of Valladolid has 1 700 seats, and is used mainly for the symphony repertoire (below, left). A chamber music hall of 500 seats (right), a 400 seats experimental theatre and a music conservatory are also included in this huge building. This project was chosen by competition with architect Ricardo Bofill in 2001 and was opened in April 2007. The acoustic need for massive ceiling materials in the halls was contradicted by the requirements. During the construction period, to keep costs down and to ensure seismic safety for the public which is facilitated by lower mass. There was little scientific, quantitative precision on the necessary specific mass. After several concerts, the musicians and audience felt satisfied with the sound´s richness, brilliance and the warmth. The chamber music hall has also a very good reaction from the users, but as yet there is no acoustic measurement of the occupied hall.

PACS: 43.55.Fw

Kahle, Eckhard; Jurkiewicz, Yann; Faillet, Nathalie; Wulfrank, Thomas; Katz, Brian FG

Kahle Acoustics; Avenue Molière 188, 1050 Brussels, Belgium; kahle_at_or_arroba_kahle.be.

A new 2400 seat concert hall is to be constructed in the Parc de la Villette in Paris, next to the existing Cité de la Musique. Kahle Acoustics, in collaboration with Altia Acoustique Paris, has been appointed as the client´s acoustician throughout the project. Our first task was to define the acoustic brief for the concert hall competition and to participate in the elaboration of the architectural brief. This paper presents the research undertaken for this project —first questioning and finally confirming the client´s brief— and will present the final acoustic brief. As the client´s brief requested an innovative acoustical and architectural concept, it was decided to not define any architectural shape, but formulate all acoustic requirements in terms of objective —both acoustic and architectural— criteria.

PACS: 43.55.Cs-Mc

Luykx, Maarten¹; Mertkemeijer, Rob²; Vercammen, Martijn¹

¹Peutz Consult, Mook, the Netherlands; m.luykx_at_or_arroba_mook.peutz.nl.
²Peutz Consult, Zoetermeer, the Netherlands; r.metkemeijer_at_or_arroba_zoetermeer.peutz.nl.

In 2006 the new theatre in Zwolle (NL) has been completed which can be considered as a next step in variable acoustics. The hall is not only suitable for intimate plays (850 seats) but also for opera and symphonic concerts (1000 seats), in all situations with natural acoustics. The variable acoustics necessary are obtained by altering the very compact volume of the theatre (about 4100 m³) into about 11000 m³ for symphonic music. Using 370 m² of movable ceilings an additional volume of about 4100 m³ above the hall is realised using an 7 m high gallery. Additionally, an orchestra shell of 2.800 m³ can be applied. A 1:12 scale model has been used in the design phase to verify the acoustic behaviour. Reactions of listeners and critics are very positive (“Masterpiece of variability”). The acoustics of the real hall have been measured in May 2007, revealing interesting properties. RT values are 0.9 s for theatre up to 2.1 s. for symphonic music. Average C₈₀(3) values range from 0 dB for concert use, 4 dB for opera up to 7 dB for theatre. The hall combines the sightlines of a theatre and its intelligibility with the reverberation of a concert hall, making it an excellent opera house as well

PACS: 43.55.Cs

Adelman-Larsen, Niels Werner¹; Thompson, Eric R.²; Gade, Anders Christian²

¹Flex Acoustics, Scion–DTU, Diplomvej, Bygn. 376, DK–2800 Kgs. Lyngby, Denmark; nwl_at_or_arroba_flexac.com.
²Acoustic Technology, Ørsted·DTU, Tech. Univ. of Denmark, Bygn. 352, Ørsteds Plads, DK–2800 Kgs. Lyngby, Denmark; [et,acg]_at_or_arroba_oersted.dtu.dk.

The existing body of literature regarding the acoustic design of concert halls has focused almost exclusively on classical music, although there are many more performances of rhythmic music, including rock and pop. Objective measurements were made of the acoustics of twenty rock music venues in Denmark and a questionnaire was used in a subjective assessment of those venues with professional rock musicians and sound engineers. Correlations between the objective and subjective results lead, among others, to a recommendation for reverberation time as a function of hall volume. Since the bass frequency sounds are typically highly amplified, they play an important role in the subjective ratings and the 63-Hz-band must be included in objective measurements and recommendations.

PACS: 43.55.Hy

Cirillo, Ettore; D´Alba, Michele; Della Crociata, Sabrina; Martellotta, Francesco

DAU – Politecnico di Bari, via Orabona 4, 70125 Bari, Italy; f.martellotta_at_or_arroba_poliba.it.

The influence of pews on the acoustical characteristics of churches is often significant because of the lack of large absorbing surfaces. The effect of occupation is even more important because the higher absorption due to people makes the acoustics dependent on the number of occupants. In order to better quantify the contribution of the pews and that of the people to the total acoustic absorption a set of measurements were carried out in a modern church with two types of pews. The measurements were carried out in four steps. First the church was measured with the pews at their places. Then the first type of pews was removed and measures repeated. Then, also the second kind of pews was removed and the measurements were made in the empty church. Finally, the measurements were repeated just before the beginning of a Mass, with an average occupation of 75%. Measurements showed that construction details such as the length and the quality of the material may influence the results, while the effect of occupancy is more significant at medium and high frequencies.

PACS: 43.55.Gx

Santiago, Francisco¹; Inácio, Octávio²

¹Master degree student in Engineering and Architecture, La Salle, Universitat Ramon Llull, Barcelona; santiagofx_at_or_arroba_gmail.com
²Musical Acoustics Laboratory, ESMAE, Instituto Politécnico do Porto, Rua da Alegria, 503, 4000–045 Porto, Portugal; OctavioInacio_at_or_arroba_esmae-ipp.pt

As in most European countries, Portugal has a long and rich history of performing arts, mainly centred on music and drama. Evidence of spaces for arts performance were found in Lisbon, in 1798, in the form of roman theatre ruins dating back to the 1st century A.D. However, it was only during the 18th century that the first Opera Houses were built in Portugal, some of them surviving almost intact and operational until today. Until the end of the 20th century more than 150 theatres and concert halls were active, a number that has been surpassed with modern buildings constructed in the last 6 years. With the continuous increase in the search for music, opera, dance and theatre performances spreading over the whole country, the need for an acoustical perspective on this patrimonial legacy was obvious. In this report we present a summary of the first thorough acoustical survey of the 33 most important theatres and concert halls distributed over 16 cities from the North to the South of Portugal. The results of measurements of reverberation time and other acoustical parameters for various source and receiver positions are presented.

PACS: 43.55.Cs

Bonsi, Davide; Stanzial, Domenico

The FSSG-CNR Acoustic Lab. c/o Fondazione Cini; National Research Council of Italy–Fondazione Scuola di San Giorgio; Isola di San Giorgio Maggiore 30124 Venezia, Italy; davide.bonsi_at_or_arroba_scuoladisangiorgio.it; domenico.stanzial_at_or_arroba_cini.ve.cnr.it.

A measurement campaign inside the Basilica di San Marco in Venice has been conducted with the purpose of characterizing the acoustical properties of some source-receiver configurations which are of interest from the historical point of view. Measurements of quadraphonic impulse responses (including sound pressure and three components of particle velocity vector) have been done with the purpose of studying the relationship between standard room acoustics indices as clarity and reverberation with the behaviour of energetic quantities.

PACS: 43.55.Gx

Tavares, Menino Allan S.M.Peter¹; Rajagopalan, S¹; Sharma, Satish Jagannath²

¹Department of Physics, Nagpur University, Nagpur – 440 033, India; allan.wholysound_at_or_arroba_gmail.com; rajag_ngp_at_or_arroba_sancharnet.in
²Department of Elect ronics, S.K. Porwal College, Kamptee, Nagpur – 441 002, India; sjsharma_at_or_arroba_rediffmail.com

The “Tranquillity” factor in Christian worship can be acoustically expressed as an optimized blend of silence, awe and intelligibility. These derived acoustic parameters in this study are called “Acoustic Comfort Impression Index” [ACII] and “Subjective Speech Intelligibility Index” [SSII] with respect to live music and speech respectively. This study presents the behaviour and optimized prediction of ACII and SSII, by subjective and objective acoustic measures, in two catholic churches of Goa coded as HSCH and HTCH respectively. ACII for different signal sources and music types and SSII for different signal sources and languages were analyzed and averaged in 4 listener zones using Excel and Origin 6.0. Terrasonde Audio Tool Box 2.0 along with Terralink and AutoCAD was used for measuring objective acoustic parameters (RASTI, RT60, D₅₀, C₈₀, TS, LEF, ITDG, EDT, G, etc.) at different locations in each church. ACII_HSCH was found higher than ACII_HTCH and best predicted by subjective clarity and objective Loudness Index while ACII_HTCH was best described by subjective reverberance and objective TS. SSI_HSCH and SSI_HTCH nearly tallied and both suitably predicted by D₅₀, C₈₀ and RASTI. These results incorporated in the early stages of design can therefore decisively create tranquillity in a church.

PACS: 43.55.Cs

Van Dorp Schuitman, J.¹; De Vries, D²

¹TU Delft, Faculty TNW, IST Department, Section of Acoustical Imaging and Sound Control, Lorentzweg 1, 2628 CJ Delft, The Netherlands; j.vandorpschuitman_at_or_arroba_tudelft.nl.
²TU Delft, Faculty TNW, IST Department, Section of Acoustical Imaging and Sound Control, Lorentzweg 1, 2628 CJ Delft, The Netherlands; d.devries_at_or_arroba_tudelft.nl.

The acoustical parameters of a room, which are supposed to predict and specify its perceptual quality, are generally assessed by performing impulse response measurements at multiple positions — or better: along an array of microphone positions. The parameter values are derived for each microphone position. One of the problems which arise from this method is the large spatial fluctuations of most parameters, which conflicts with listening tests showing that perception does not vary that much. Using Continuity Preserving Signal Processing (CPSP), a time frequency analysis of a signal can be performed using a mathematical model of the human cochlea, while continuity is preserved both in time and in frequency. This form of signal processing is already successfully applied in auditory scene analysis applications, like speech recognition. It is believed that applying this technique to impulse response measurements might lead to results that are closer to human perception, not suffering from large spatial fluctuations. In the CPSP domain, acoustical parameters can be derived in such a way that perceptual effects like frequency masking are taken into account.

PACS: 43.55.Hy

Berntson, Alf¹, Andersson, Johan²

¹Artifon AB, Gothenburg, Sweden; alf_at_or_arroba_artifon.se.
²Student at Chalmers University of Technology, Gothenburg, Sweden; ajoha_at_or_arroba_student.chalmers.se.

This investigation was made in collaboration with a professional symphony orchestra, with the goal of improving the acoustics at their home stage. A pre-study through questionnaires was conducted during a tour. The outcomes were used to design the first stage configurations, evaluated during the early part of a tuning week. Binaural impulse responses were measured for 14 configurations from five positions on stage to five musicians and to a dummy head in the audience. After performing seven pieces of music, all musicians judged the stage acoustics in a questionnaire. The music was recorded binaurally and the A-weighted sound pressure levels were evaluated. The musicians judged the sound level to be much lower in the final configuration. However, the binaurally measured sound pressure levels from the music played show very small differences. The measured sound level is probably mainly determined by the sound from the own instrument and the closest surrounding instruments. The judged level is probably based on the later arrived sound level and the character of the sound. Generally the judgements are highly scattered and the correlations between subjective judgements and standardized parameters like Support, Clarity, EDT, IACC etc is low.

PACS: 43.55.Cs

Billon A.¹; Foy C.¹, Valeau V.², Picaut J.³ , Sakout A.¹

¹LEPTAB Université de La Rochelle, Av. M. Crépeau, 17042 La Rochelle cedex, France; abillon_at_or_arroba_univ-lr.fr.
²LEA UMR CNRS 6609, 40 Av. du Recteur Pineau, 86022 Poitiers Cedex, France.
³Laboratoire Central des Ponts et Chaussées, Route de Bouaye, B.P. 4129, 44341 Bouguenais Cedex, France

The diffusion model has been used successfully to evaluate the acoustic behaviour of a system of coupled rooms connected through a coupling aperture. In this paper, an extension of this model is proposed to deal with the propagation of sound energy through a partition wall. The diffusion model can be considered as an extension of the statistical theory to none diffuse sound fields. Numerical comparisons with the statistical theory are then carried out. The following parameters are varied: its transmission loss of the separation wall, its surface, the coupled room´s absorption coefficient and the coupled room´s volume. The agreement between the statistical theory and the diffusion model is very good.

PACS: 43.55.Ka

Tokita, Yasuhiro¹; Oikawa, Yasuhiro²; Yamasaki, Yoshio³

¹Waseda Environmental Research Institute, Waseda Univ.; 1011 Okuboyama, Nishitomida, Honjou, Saitama, 367–0035, Japan; y-tokita_at_or_arroba_waseda.jp.
²Department of Intermedia, Art and Science, Faculty of Science and Engineering, Waseda Univ., 3–4–1 Okubo , Shinjuku, Tokyo, 169–8555, Japan; yoikawa_at_or_arroba_waseda.jp.
³Graduate School of Global Information and Telecommunication Studies, Waseda Univ., 1–3–10 Nishi-Waseda , Shinjuku, Tokyo, 169–0051, Japan; y-yamasaki_at_or_arroba_waseda.jp.

In order to reduce the amount of communication among each node of the computer cluster on parallel computing, we proposed a method to divide the field of numerical analyses. It was called “bread slicing method”. With this method, the fields must be divided into pieces parallel to the section that has the least area. Generally, on the parallel computing of the distributed memory system, the communicating time occupies most of the total calculating time. Therefore, the reduction to the amount of the communication directly causes the reduction of the calculating time. Numerical analyses by the explicit scheme of the finite difference method greatly reduce the number of known variables that are needed to solve an unknown variable in comparison with the implicit methods. The parallel computing by the explicit scheme of the finite difference method can enable the building up of high-performance algorithms. The results showed that the method enabled the total amount of communication in the computer cluster to be reduced and the geometries of communication to be made simpler. In this study, the efficiency of parallel computing by the method is evaluated. The values of the efficiency are shown the advantage of the method.

PACS: 43.55.Ka, 43.55.Br, 43.58.Ta, 43.20.Fn

Redondo, J.¹, Picó R.¹, Avis M. R.²

¹Universidad Politécnica de Valencia. Cr. Nazaret-Oliva S/N. Grao Gandía (Spain) fredondo_at_or_arroba_fis.upv.es.
²Acoustics Research Centre. University of Salford. Salford M5 4WT. (UK).

Since the invention of sound diffusers three decades ago a substantial effort has been made to predict the acoustic behaviour of these structures in response to the large costs inherent in anechoic measurements. Volumetric methods such as Finite Element Methods (FEM) or the Finite Difference Time Domain method (FDTD) are not often used, due to their large computational cost. However Near Field to Far Field Transformations (NFFFT) can overcome that problem. The main advantages of the FDTD method are that a single calculation is sufficient to study a wide frequency band, and that the time domain behaviour of the reflected sound can be directly inspected. On the other hand the inclusion of the well separators vibration can be made in a straightforward way, in order to estimate its significance on the scattering provided by diffusers. Additionally, active elements can be easily introduced in the simulation in order to evaluate directly the performance of an active diffuser. In the present paper we estimate the potential of FDTD to predict the acoustic behaviour of sound diffusers.

PACS: 43.55.Ka

Vigeant, Michelle C.; Wang, Lily M.

Architectural Engineering Program, University of Nebraska – Lincoln; Peter Kiewit Institute, 1110 S. 67th St., Omaha, NE 68182-0681, USA; mvigeant_at_or_arroba_mail.unomaha.edu, lwang4_at_or_arroba_unl.edu.

An orchestra can be simulated in room acoustics computer modelling using a variety of methods, ranging from a single omni-directional source to individual sources of all instruments. This study utilizes the method of individual sources for each instrument, but with reduced source representation for the string sections. The anechoic recordings used in this investigation are five-channel recordings, which capture the source directivity of the individual instruments. For each string section, the individual anechoic recordings were phase shifted several times, up to 23 ms, and combined to create a single recording for use in the simulations. An orchestra was simulated in three different configurations — American (first and second violins adjacent), European (first and second separated) and a completely random arrangement. For each configuration, auralizations were created using a single channel and five-channel representation for each instrument or section and for both a Brahms and Mozart symphony. Listening tests were conducted to determine if subjects could detect differences in auralizations created using the three different orchestra configurations. Preliminary results from this pilot study show subjects can detect differences between some of the configurations, particularly the American versus Random, and European versus Random, with more of an effect with Brahms than with Mozart.

PACS: 43.55.Ka

Alarcão, Diogo; Bento Coelho, J. L.

CAPS – Instituto Superior Técnico, Av. Robisco Pais 1, P-1049-001 Lisbon, Portugal; diogo.alarcao2ist.utl.pt.

A new combined model for the propagation of sound energy inside arbitrarily shaped rooms is presented. The walls of the arbitrary rooms are composed of reflecting surfaces, which reflect the sound energy as a mixture of specular and diffuse components. This new combined model uses a pure image source method with statistical extensions for high reflection orders and a time-dependent hierarchical radiosity method. The image source method models the propagation of the specularly reflected energy component, while the radiosity method calculates the propagation of the diffusely reflected energy components. Both methods operate independently from each other. The predicted room impulse responses are obtained through combination of the individual results from each method. Several algorithmic improvements are introduced in the computer implementation of this combined model

PACS: 43.55.Ka

Kowalczyk, Konrad; van Walstijn, Maarten

Sonic Arts Research Centre (SARC); School of Electronics, Electrical Engineering and Computer Science Queen´s University Belfast, BT7 1NN Belfast, Northern Ireland kkowalczyk01_at_or_arroba_qub.ac.uk; m.vanwalstijn_at_or_arroba_qub.ac.uk.

This paper presents a new model for modelling locally reacting walls, that can be used in finite difference modelling of acoustic spaces. The new 2D/3D finite difference boundary formulation is compared to the more conventional 1D formulation in terms of pressure wave reflection for different wall impedances and angles of incidence. The results show that the 2D formulation adheres significantly better to the continuous-time formulation for all angles of incidence than the 1D formulations; in particular, it is shown that only the 2D formulation properly preserves the phase.

PACS: 43.55.Mc

Farnetani, Andrea¹; Prodi, Nicola¹; Pompoli, Roberto¹

¹Engineering Dept., University of Ferrara, Via Saragat 1, 44100 Ferrara, Italy; andrea.farnetani_at_or_arroba_unife.it.

In previous works the acoustical behaviour of ancient Greek and Roman open air theatres was outlined by means of both in situ acoustical measurements and scale model studies. Moreover, a simplified phase image source model was developed to predict the sound level within ancient theatres. It was found that wave effects are not negligible in these spaces and the scattering of the steps was demonstrated to play an important role. The above findings prompted to further investigate the diffraction caused by the tiers of steps in open air ancient theatres, from the experimental and numerical point of view. Thus, a sample of ancient theatre´s cavea was modelled and its scattering and diffusion coefficients were measured both in a diffuse and a free sound field. The obtained scattering data are relevant in the contest of numerical ray tracing modelling of performance spaces and in particular of open air theatres where their impact seem of paramount importance.

PACS: 43.55.Mc

Rafaely, Boaz; Koretz, Amitai; Winik, Roni; Agmon, Morag

Department of Electrical and Computer Engineering, Ben-Gurion University of the Negev, Beer Sheva 84105, ISRAEL; br_at_or_arroba_ee.bgu.ac.il.

Spherical microphone arrays have been recently studied for sound-field analysis in auditoria. Beamforning was employed for spatial separation of individual reflections from the stage to the seating area, therefore providing detailed spatial mapping of sound propagation. In this work beampattern design for spherical microphone arrays is employed to achieve improved analysis of the sound field. Spatial —spectral— temporal trade-offs in the sound-field analysis will be discussed. Finally, experimental results from auditorium measurements will be presented.

PACS: 43.55. Fw, Mc

Keiji, Oguchi

NAGATA ACOUSTICS Inc.; 2130 Sawtelle Blvd., Suite 307A, Los Angeles, CA, 90025, USA, oguchi_at_or_arroba_nagata.co.jp.

A miniature loudspeaker assembly has been manufactured for acoustical scale model testing using parts for a commercially available studio monitor headphone. The loudspeaker assembly consists of a dodecahedron loudspeaker for middle and high frequency sounds and woofers for low frequency sounds, respective to the scaling required for a scale model test. The loudspeaker can reproduce sound with a frequency range from 1kHz to 80kHz (with an nearly flat response from 2kHz-40kHz), equivalent from 100Hz to 8kHz for a 1/10 scale model test. The frequency and directional characteristics of the miniature loudspeaker assembly are discussed in this paper, and some scale model test examples are introduced.

PACS: 43.55.Hy

Nils-Ǻke, Andersson¹; Erling, Nilsson²

¹Saint-Gobain Ecophon AB; nilsake.andersson_at_or_arroba_ecophon.se.
²E. Nilsson Akustik; erling.nilsson_at_or_arroba_bredband.net.

More and more people recognize that reverberation time does not on its own express the subjective experience of a space. Calculated reverberation time differs in many cases from the measured one. A systematic check of room acoustics in 19 classrooms has therefore been performed. These classrooms were situated in Denmark, Germany, Norway and Sweden. Big efforts were put on setting up a detailed measurement protocol, with established and well recognized parameters. Except a lot of physical measurements, recordings of female and male speakers in English and Swedish were included. In each classroom measurement was executed with at least two different acoustic ceiling solutions, all with and without furniture; also the empty room was checked. Results show that reverberation time might be almost equal with acoustic ceilings having substantially different sound absorption properties. This is especially noticeable in mid and higher frequencies. The correlation with traditionally calculated reverberation time is poor. On the other hand the decrease of sound pressure level from a steady state source can be estimated proportional to the amount o f sound absorption in the room.

PACS: 43.55.Gx

You, Jin¹; Sato, Shin-ichi²; Jeon, Jin Yong³

School of Architectural Engineering, Hanyang University, Seoul 133-791, Korea. ¹jinyou.willow_at_or_arroba_gmail.com; ²s_sato_at_or_arroba_mac.com; ³jyjeon_at_or_arroba_hanyang.ac.kr.

Acoustical qualities of Sejong Chamber Hall (476 seats) were evaluated in the hall and in the laboratory conditions. In case of in-situ experiments, violin music source recorded in an anechoic chamber was presented using an omnidirectional loudspeaker on the stage and subjects were asked to evaluate acoustical aspects at 8 different seats of the hall. The seats were chosen according to sound pressure level (SPL) and interaural cross-correlation coefficient (IACC) in order to investigate the effects of sound energy and IACC on spatial impressions. The same procedure as the in-situ experiments was applied to the laboratory condition experiments. In order to reproduce the sound fields of the actual hall, stereo dipole system including a cross-talk cancelling was introduced. The results of in-situ experiments were compared with those of the laboratory experiments to validate their results. By the experiments, effects of SPL and IACC on subjective responses of listener envelopment (LEV) were clarified.

PACS: 43.55.Cs

Griesinger, David

Harman Specialty Group, 3 Oak Park Drive, Bedford, MA 01730 dgriesinger_at_or_arroba_hsgav.com.

This paper presents the results of a series of binaural experiments into the audibility of the direct sound in a range of listening positions and hall geometries. Although in a typical hall more than half the seats have a direct to reverberant ratio (d/r) of less than -10dB, in the best halls the direct sound is distinctly audible over a wide range of seats. When this is the case a majority of the seats experience high clarity, low perceived distance to the performers, good azimuth localization, and high envelopment. We find that the detection of direct sound depends critically on the d/r and the time gap between the direct sound and the time that the reverberation from a continuous excitation builds up to 1/10th the final energy. When this gap is small — due to the size and dimensions of the hall — higher values of d/r are necessary for good sound. The data presented allow a hall designer to optimize the seating distance, RT, and hall shape for best results.

PACS: 43.55.Cs

Jeon, Jin Yong¹ ; Sato, Shin-ichi²

School of Architectural Engineering, Hanyang University, Seoul 133-791, Korea; ¹jyjeon_at_or_arroba_hanyang.ac.kr; ²s_sato_at_or_arroba_mac.com

This study investigates the optimum parameter settings in the computer models. Model fitting was carried out in terms of RT, EDT, C₈₀, and T_s. Acoustical parameters calculated by ODEON program were compared with those measured in a 1:50 scale model of shoebox and fan-shaped halls. Wooden hemispheres were installed on the side walls of the scale model. The results of the computer simulation showed that a 30% reduction in the absorption coefficients from the reverberation chamber measurement gave the minimum error for flat surfaces while a 25% reduction for the hemisphere diffusers in terms of RT, EDT, C₈₀, and T_s. We also investigated the effect of the transition order on the acoustical parameters; however, there was little difference between the transition order 0 and 1. There was no significant difference between shoebox and fan-shaped halls.

PACS: 43.55.Gx

Yilmaz Karaman, Ozgul

Dokuz Eylul University, Faculty of Architecture, Buca, Izmir, Turkey; ozgul.yilmaz_at_or_arroba_deu.edu.tr

Drama theatres are expected to answer the need of intangible and relatively indefinable architectural qualities such as mood, intimacy, magic and memory as well as the acoustical requirements, more than any other building types. Besides this, often, non-acoustic phenomena such as the view from the occupied seat, the comfort of the seat itself, the thermal comfort of the environment etc. can also influence the overall judgment (Cocchi, Farina, Fausti and Tronchin). So, to obtain best design for a drama theatre, both acoustical and visual comfort must be considered carefully. Because, as I tried to describe above, theatrical performances are expected to satisfy the spectators in terms of both auditory and visual comfort conditions. And in this paper, I wanted to focus on beginning of theatre art and design. Because, looking at the past still can be a very useful way to find answer some questions about what we are trying to learn.

PACS: 43.55.Hy

Orfali,Wasim¹; Ahnert, Wolfgang²

¹ ITA, TU; Einsteinufer 25, Berlin, Germany; Orfaliwasim_at_or_arroba_Hotmail.com
² ADA Acoustic design Ahnert, Arkonastr. 45-49, Berlin; wahnert_at_or_arroba_ada-acousticdesign.de

High speech intelligibility in mosques is an essential aim for any efficient sound system design. If the intelligibility levels are low, Praying and Preaching in such structures will loss the attention of the congregation. There are different ways to increase the intelligibility levels. The most traditional solution is to decrease the reverberation time by means of wall and carpet treatments “Passive Treatments”. More advanced solution is to use modern loudspeakers columns to increase the direct to reverberant field ratio “Active Treatment”. The big volumes and high ambient noise in mosques have made it necessary to enforce high intelligibility levels using modern sound reinforcement systems. In this work a real life example will be provided to show the influence of using directed loudspeakers columns in contrast to conventional sound sources. The improvement of intelligibility levels inside the main praying hall of Sheikh Zayid Mosque in Abu Dhabi using Digitally Controlled Sound Columns is demonstrated. The ability of such modern loudspeakers to address different praying modes is shown too.

PACS: 43.55.Fw

Briones Ramos, Juan José

Briones Ingeniería Acústica; Costa Rica P11/6 N3, Polígono Industrial Oeste, Apdo.139, 30169, San Ginés, Murcia, Spain; briones_at_or_arroba_biacustica.es

Three sound recording and postproduction studios were projected and built in the past three years. The control room design was based on LEDE (Live end-Dead end) concept [1]. Each studio presents differences in budget, space limitations, professional audio requirements (stereo - multichannel) and uses (sound recording - sound postproduction - mixing). In this paper we apply a method to evaluate the subjetive quality of each one, and expose the opinions of professionals about the studios´ quality. The quality of studios is obtained attending to room´s geometry and size, background noise, sound diffusion degree, reverberation time and LEDE design.

PACS: 43.55.Hy

Sato, Shin-ichi¹; Kim, Yong Hee²; Jeon, Jin Yong³

School of Architectural Engineering, Hanyang University, Seoul, 133-791 Korea; ¹s_sato_at_or_arroba_mac.com; ²kimyonghee_at_or_arroba_gmail.com; ³jyjeon_at_or_arroba_hanyang.ac.kr

This paper investigates the effects of diffuser locations on sound field in a hall. A 1:25 scale model of a multi-purpose hall with 600 seats was used. Objective evaluation of sound field was carried out through measurement of acoustical parameters (RT, EDT, C₈₀, G, and T_s). 375-mm diameter (in real scale) hemisphere diffusers were installed in the scale model hall. Impulse responses were measured under conditions with and without diffusers. Seven cases according to different diffuser locations (balcony front, ceiling reflector, lateral walls and their combinations) were considered. The absorption power increases as the number of diffuser is increased. Thus, the results of the measurement show that RT decreases as the number of diffuser is increased. Diffusers installed on the balcony front decreased EDT at the first floor. Decrease of EDT was larger than that of RT. Diffusers installed on ceiling reflectors increase EDT and decrease G at rear seat of the second floor, while the ceiling diffusers decrease EDT and increase G at frontal seat of the first floor. Diffusers on lateral walls close to stage decrease early sound energy, but diffusers on lateral walls at rear seats supplement the early reflections by redirection of sound ray.

PACS: 43.20.Mv

Pelat, Adrien¹; Ayrault, Christophe; Richoux, Olivier; Felix, Simon

LAUM, CNRS, Université du Maine, 72085 Le Mans, France ¹adrien.pelat.etu_at_or_arroba_univ-lemans.fr

In this study we are concerned with a multimodal formulation of the acoustic propagation in long enclosures, considered as waveguides. Two infinite sets of coupled first-order differential equations are constructed for the components of the pressure and axial velocity, projected on the local transverse modes. These equations are ordinary differential equations that can be integrated after truncation at a sufficient number of modes and take into account the coupling between modes. Such a method appears to be particularly adapted to take into account geometrical (cross-section) or physical (boundary condition) non-uniformities in the waveguide, as well as the radiation or continuity conditions at the extremities. The formulation and main properties of a multimodal approach of the sound propagation in a room or urban acoustics context will be discussed. Numerical illustrations on 2D examples will also be given, as well as measurements from a scale model experiment.

PACS: 43.20.Mv

Félix, Simon¹ ; Pelat, Adrien ; Pagneux, Vincent

LAUM, CNRS, Université du Maine, 72085 Le Mans, France; ¹simon.felix_at_or_arroba_univ-lemans.fr

A long enclosure being regarded as a waveguide in which the sound, generated by some source, may propagate, one is interested in a multimodal approach of the sound propagation within this waveguide, as it may be particularly adapted to take into account geometrical (cross-section, curvature) or physical (boundary condition) non-uniformities in the waveguide, as well as the radiation or continuity conditions at the extremities. A key point in such multimodal formulation is the choice of the basis of local transverse modes, on which the wave field is projected. In “classical” waveguides having a simple and bounded cross-section, a complete orthogonal basis of eigenmodes can be analytically obtained. The case of an open waveguide is more difficult, since no such a basis can be exhibited. However, an open resonator, as displays the cross-section of an open waveguide, is known to also exhibit resonant modes, with complex eigen-frequencies, owing to the radiative losses. In the present study it is shown how these modes, than can be numerically evaluated, can be used to establish a multimodal formulation in an open waveguide modelling a long rectangular enclosure.

PACS: 43.55.Br

Nowicka,Elzbieta

Building Research Institute, Department of Acoustics; Ksawerow Str. 21, Warszawa, Poland; E.Nowicka_at_or_arroba_itb.pl

In the acoustic literature there is a lot of parameters and methods to asses acoustic climate of any room. The reverberation time is one of the most famous and commonly used method. There is some of literature concerning the acoustic conditions of underground stations, but still there is a lack of knowledge about methods allowing the correct estimation of the reverberant conditions of this kind of enclosures. This paper compares results of reverberation times (EDT, T20 and T30) in the Warsaw´s underground stations with Sabine´s, Norris – Eyring´s, Knudsen´s and other formulas. This comparison indicated that calculations may give incorrect reverberation time values, especially in long enclosures with reflective boundaries. In the paper there is also presented the dependence of the reverberation time on the source – receiver distance for the enclosures with reflective boundaries.

PACS: 43.55.Cs

Adelman-Larsen, Niels Werner¹; Thompson, Eric R.²; Gade, Anders Christian²

¹Flex Acoustics, Scion-DTU, Diplomvej, Bygn. 376, DK-2800 Kgs. Lyngby, Denmark; nwl_at_or_arroba_flexac.com
²Acoustic Technology, Ørsted·DTU, Tech. Univ. of Denmark, Bygn. 352, Ørsteds Plads, DK-2800 Kgs. Lyngby, Denmark; [et,acg]_at_or_arroba_oersted.dtu.dk

Multi-purpose concert halls face a dilemma. They host different performance types that require significantly different acoustic conditions in order to provide the best sound quality to both the performers, sound engineers and the audience. Pop and rock music often contain high levels of bass sound energy but still require high definition for good sound quality. The mid- and high-frequency absorption is easily regulated, but adjusting the low-frequency absorption has typically been too expensive or requires too much space to be practical for multi-purpose halls. A practical solution to this dilemma has been developed. Measurements were made on a variable and mobile low-frequency absorber. The paper presents the results of prototype sound absorption measurements as well as elements of the design.

PACS: 43.55.Cs

Šumarac Pavlović, Dragana ; Mijić, Miomir

Acoustic Laboratory, Faculty of Electrical Engineering, Belgrade, Serbia;

Room geometrical properties have some influence on the acoustical response and they must be considered mutually on the two levels, macro level of global geometrical shape and micro level of geometrical structured of the interior surfaces [1]. That influence can be quantified by the variations of the reverberation time from the statistical expected values. Common way of quantifying the geometrical characteristics of a room is the mean value and relative variance of the free path length distribution (FPL). To test significance of these parameters as indicators of room acoustic response, 51 software models of various rooms were prepared. FPL distribution was calculated using ray-tracing analysis, and also their mean values and relative variance. Conclusion were made that these parameters have not enabled accurate distinctions among the differences found in the FPL distribution shapes and accordingly among the different acoustic responses. That is why two more parameters common in mathematical analyses of probability curves were introduced in this analysis: skewness (“the asymmetry coefficient”) γ₁ and kurtosis (“the flatness coefficient”) γ₂. Analyses have shown that the values of γ₁ and γ₂ make a better distinction among the rooms with different shapes and better prediction of reverberation time.

PACS: 43.55.Cs

Ahnert, Wolfgang; Feistel, Stefan; Miron, Alexandru; Finder, Enno

Ahnert Feistel Media Group, Berlin, Germany

In previous publications the authors introduced the software based measuring system EASERA to be used for measurements with pre-recorded music and speech signals. This second part investigates the use of excitation signals supplied from an independent external source in real-time. Using a newly developed program module live-sound recordings or speech and music signals from a microphone input and from the mixing console can be utilized to obtain impulse response data for further evaluation. New noise suppression methods are presented that allow these impulse responses to be acquired in full-length even in occupied venues. As case studies, acoustic measurements based on live sound supply are discussed for a concert hall and a soccer stadium. Required measuring conditions and limitations are derived as a result.

PACS: 43.55.Cs

J Newton & R Harris

Arup Acoustics, 8 St Thomas Street, Winchester, Hampshire SO23 9HE, UK. www.arup.com/acoustics

This paper describes the acoustic design of the main auditorium (Store Sal) of the new national opera house in Oslo. The paper summarises the design aims and explains how the overall geometry, detailed geometry and choice of materials were selected to mean these design aims.