885095987

Contributed Papers

10:30

4AA4. Subjective and objectite evaluations of c lass rooms and lecture halls. Wei-hwa Chiang, Gary W. Siebein, and Richard P. Cen/one (Dcpt. of Arch., 231 ARCH. Univ. of Florida, Gainesville, FL 32611)

Speech intelligibility tests were given to groups of college studenta in ten classrooms and lecture halls of various sizes on the University of Florida campus. A series of acoustical measurements including rever-beration time, early reverberation time, loudness, carły to late tempo rai energy ratios, lateral energy fractions, interaural cross correlation, and speech transmission index were madę at multiple locations in each of the rooms. Correlation analysis and statisticaJ modeling identified sig-mficant relationships among intelligibility scores of the listeners with the physical measurements madę in the room. Special attention was given to the architectural characteristics of the rooms in the analysis. The variations in intelligibility scores and the physical measurements among the different rooms and within each of the rooms are presented. [Work supported by NSF.]

10:45

4AA5. Modern acoustic measurements on three types of concert platforms. John P. M. 0’Keefe and Marc Bracken (Barman Swallow Assoc., 1 Grcensboro Dr., Rexdale, Ontario M9W IC8, Canada)

Recent studies, particularly those by Gade and Naylor, have begun to quantify the acoustical requirements of performers on stage as ex-pressed in measurable acoustic parameters. These parameters, originally based on laboratory findings, are now being measured in real concert halls. The purpose of this investigation is to add to this database by mcasuring the conditions on three different types of concert platforms: A proscenium theatre stage, a multipurposc room with a reflector above the stage, and finally, a traditional concert hall stage. Measurements in the multipurpose room will also quantify the effect of reflector łieight above the stage in terms of support (ST₁₀₀) and modulation transfer functions. Measurements in the proscenium theatre will quantify conditions on stage, in the orchestra pit, and between the stage and the pit.

11:00

4AA6. Experimental measurements of auditoiia acoustic quality. A.

Cocchi, P. Fausti, and M. Garai (Inst. di Fisica Tecnica, Univ. di Bologna, Viale Risorgimento 2, 40136 Uologna, Italy)

This paper illustrates an original implementation of Ando’s theory for the evaluation of the acoustical characteristics of concert halls. In most cases, preliminary research is carried out on physical scalę models in order to identify the temporal distribution of the various reflections into the room, or using a ray tracing program whieh can also compute other important acoustic descriptors. The following measurement procedurę inside the hall is cnmpletely automatized: The data are acquircd via an artiflcial head carrying two microphones in the place of the ears; the head is linked to a two-channel FFT analyzcr that performs a digital analysis of the signals under control of a microcomputer that also com-plctes somc parts of the computation. This fast, in situ elaboration of the data, make it possible to carry out in a short time many measurements in different points of the hall and to obtain for each of them the four parameters of the Ando’s theory (IACC, ITDG, L_A). From these values, a pre/erence index can be determined for each point inside the room. The above mentioned techniqucs havc already been used to qual-ify and to compare different kinds of theatres and auditoria.

11:15

4AA7. Scale-model acoustical analysis of the Performing Arts Center at SwarthmoreCollege. Ming Hin Soon and E. Carr Everbach (Dcpt. of Eng., Swarthmore College, Swarthmore, PA 19081-1397)

The Lang Performing Arts Center is a ncwly constructed facility that will housc the Dcpartmcnts of Drama and Dance at Swarthmore College. The facility contains a 1000-seat theater with adjustable staging and a moveable concrete wali that can bisect the space into two separate thealers for simultaneous use. A 1/48 scalę model of the theater has been constructed and an analysis of the model and a comparison of the model and measurements madę in the theater itself are presented. Of special interest are some of the devices that were developed to provide acoustic excitation in the model and in the full-scale theater.

11:30

4AA8. Experiroental e?aluation of the backscattered polar response of sound absorbing, reflecting, and diffusing materials. Peter D'Antonio (RPG Diffusor Syst., Inc., 12003 Wimbleton St., Largo, MD 20772)

The sound that we hcar in a room is a combination of the direct sound and indirect reflccted sounds from room boundaries. Because the amplitudę, directionality, and temporal distribution of the indirect reflections affect how one percdves the actual sound source, control of room reflections using absorption, reflection, and diflusion is a central consideration in acoustical design. Effective application of these ingre-dients is based on an understanding of the backscattered directional response for a given angle of incidencc, angle of observation and fre-quency, i.c., the backscattered polar response. To evaluate the expcri-mcntal polar response a testing techniąuc using time delay spectrometry was developed [P. D’Antonio and J. Konnert, AES Preprint 2295, 79th AES, New York (October 1985)]. The method allows the evaluation of the backscattered frcquency response of a sound modifying materiał mounted on the boundary surface at any scattering angle, for a given angle of incidence. For sound absorbing materials, for example, these “directional” scattering coeflicients augment the traditional random-incidence ASTM reverberation chamber data. The tcchnique will be described and polar response data for sound absorbing, reflecting, and QRD^,J diffusing panels will be presented. An alternativc method using sound intensity will also bcdiscussed and preliminary data presented.

11:45

4AA9. Acoustical design of the National Center for the Performing Arts of Peru. Carlos R. Jimenez-Dianderas and Manuel Panduro-Manrique (Garcilaso de la Vega 163, Salamanca de Monterrico, Lima 3, Peru)

The projcct is based on the design of a cultural complex for the National Center for the Performing Arts which includes a 1200-seat opera house, a 750-seat concert hall, a smali auditorium for master classes, and an amphitheatre for 1500. The interest in this projcct came from the lack of cultural facilities in Peru. Furthermore, it is an estab-lished methodological altemative to the architectural acoustic design; so the Center is the result of the integrity of a two-design process combined into one architectural and acoustical design. The site for the project was determined from the cvaluation of several possibilities through analysis of successive approximations. The analysis includes the urban acoustical study of the metropolitan area of Lima. The finał dccision about the site was done through acoustical measurements of urban noise. The acoustical design of the auditoria includes ray-diagram analysis, reverberation time, early decay time calculation, and finał sound level in some posi-tioas.

1898 J. Acoust. Soc. Am., Vol. 89, No. 4. Pt 2. April 1991

121st Meeting: Acoustical Society of America 1898