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Thursday Morning, 1 December 2016 Lehua, 8:30 Am THURSDAY MORNING, 1 DECEMBER 2016 LEHUA, 8:30 A.M. TO 11:30 A.M. Session 4aAA Architectural Acoustics: Assorted Topics in Architectural Acoustics I Shinsuke Nakanishi, Cochair Department of Engineering, Hiroshima International University, 5-1-1, Hiro-koshingai, Kure 737-0112, Japan David S. Woolworth, Cochair Oxford Acoustics, 356 CR 102, Oxford, MS 38655 Contributed Papers 8:30 sound strength G and the center time Ts, have been estimated through ana- lyzing the impulse responses measured in each auditorium. These parame- 4aAA1. Design, construction, and evaluation of an omni-directional ters were spectrally averaged according to the most accepted criteria for loudspeaker (Dodecahedron). Maryam Landi, Vahid Naderyan (Dept. of sound quality evaluation in auditoriums and were expressed as a function of Phys. and Astronomy & National Ctr. for Phys. Acoust., Univ. of MS, source-receiver distance. The experimental results were compared with pre- NCPA, 145 Hill Dr., University, MS 38677, [email protected]), and dictions by classical and existing theoretical models proposed for concert David S. Woolworth (Roland, Woolworth & Assoc., Oxford, MS) halls and churches. A semi-empirical model based on the measured values Dodecahedron loudspeaker (Dodec) is an omni-directional sound source of early and late sound levels is proposed in this work. The good agreement in the shape of a 12-sided loudspeaker with each side being a pentagon. The between predicted values and experimental data of clarity, definition, sound omni-directionality of this sound source makes it mainly applicable in room strength, and center time in the auditoriums analyzed indicates that the acoustical and sound insulation measurements and research as it can excite newly proposed model can be used for design predictions with reasonable and saturate the room as much as possible. Dodec is a good approximation accuracy. of a point sound source. Commercially available omni-directional loud- 9:15 speakers are not economically efficient for some purposes. This paper out- lines a simple and inexpensive Dodec loudspeaker designed, constructed, 4aAA4. Elucidation of a mechanism of acoustic impedance technique and evaluated using ISO 140 and ISO 3382 standards as reference as part of using two cardioid microphones and ensemble averaging method. an independent coursework. The Dodec was evaluated in an anechoic cham- Kazuma Hoshi and Toshiki Hanyu (Dept. of Architecture and Living ber. The measured directivity of this Dodec meets the standards for omni- Design, Nihon Univ., 7-24-1, Narashinodai, Funabashi, Chiba 2748501, directionality at all frequencies. Japan, [email protected]) 8:45 Recently, there is growing need for in-situ impedance measurement of several materials. We propose using two cardioid microphones (called C-C 4aAA2. Room acoustic measurement techniques for large venues sensor) for it. C-C sensor has many advantages against two omnidirectional Jason R. Duty, Jeremy L. (greater than 10,000 cubic meters) in 2016. microphones (called P-P sensor) and one omnidirectional microphone and Decker, and Peter K. Holst (Charles Salter Assoc., 130 Sutter St., Fl. 5, San sound velocity (called P-U sensor). I reported the possibility of using C-C Francisco, CA 94104, [email protected]) sensor for measuring acoustic impedance on 12th Western Pacific Acoustics From sine sweeps to maximum-length sequence (MLS) type signals, Conference 2015 (WESPAC2015) and International Congress on Acoustics balloon explosions to the yachting cannon, options to measure room acous- 2016 (ICA2016). When measuring some porous materials, C-C method can tics in large venues have increased over the past couple of decades. There measure acoustic impedance as same as using P-P method, and C-C method are new developments by academia and equipment manufacturers, as well can do it from 100 Hz to over 10 kHz. Next, we tried to elucidate the mecha- as improvements on older methods. What are these new methods? What nism of using C-C sensor and Ensemble Averaging (EA) method using nu- acoustical characteristics can one measure with each method? This presenta- merical experiments. As a result, the range in application of C-C sensor for tion describes the different source options to measure room acoustical char- measuring acoustic impedance was clarified. In this presentation, we’ll acteristics in larger spaces. introduce the measuring technique and mechanism. 9:00 9:30 4aAA3. Acoustical energy relations in auditoriums. Jianliang Gao, Shiu- 4aAA5. Absorption coefficient: Dead or alive? Results of the “ASTM Keung Tang (Bldg. Services Eng., The Hong Kong Polytechnic Univ., Rm. C423 Inter Laboratory Study". Ronald Sauro (NWAA Labs, Inc., 90 ZS801, 8/F, Block Z, 181 Chatham Rd. South, Hunghom, Kowloon 999077, Tower Blvd., Elma, WA 98541, [email protected]) Hong Kong, [email protected]), and Yuezhe Zhao (State Key Lab. of Subtropical Bldg. Sci., South China Univ. of Technol., Guangzhou, In 2009 and 2011, papers were presented questioning the procedures used to measure absorption and the conversion to an “Absorption Coef- Guangdong, China) ficient.” Part of the problem was the results of these conversions resulted in Extensive objective energy-based parameters have been measured in coefficients above 1.0. These results indicated a problem with the process or three auditoriums (2 scale models and 1 site survey) in the present study. with the conversion to an “Absorption Coefficient.” Since that time enough Mono-aural measurements in the frequency range from 125 Hz to 4000 Hz data have been presented to the ASTM to result in an Inter Laboratory Study (octave band) were conducted in unoccupied auditoriums according to the (ILS) on the efficacy of ASTM C-423 and other similar worldwide stand- standard ISO 3382-1: 2009. Acoustical parameters, namely, the clarity C80, ards. Many corporate and independent laboratories took part in this study the definition D50, the early sound level Le, the late sound level Ll, the and the results of this ILS will be presented in this paper. These results 3236 J. Acoust. Soc. Am., Vol. 140, No. 4, Pt. 2, October 2016 5th Joint Meeting ASA/ASJ 3236 helped show that the process of measuring absorption and the calculation of needed to calculate speech intelligibility indices for speech intelligibility the “Absorption Coefficient” has had a basic flaw in it ever since it was first and speech privacy. In open offices, sound-level reductions per distance proposed in the 1920s. Proposed changes are discussed as well as proposed doubling (DL2) were measured. Noise isolations of internal partitions of dif- new calculations for use in calculating absorption in rooms. This should ferent designs (double-plasterboard construction, modular or built in-situ, result in more accurate and consistent calculations of reverberation times rising to the suspended ceiling or to the floor-ceiling slab, without and with for acoustic consultants. It is hoped that these results will result in a new doors, different amounts of glass) were measured. The acoustical character- standard for these measurements. istics were compared to design criteria to evaluate their acceptability. The results are presented, and are related to room type and partition design. An 9:45 empirical model for predicting partition noise isolation, developed using regression techniques, is discussed. The knowledge gained from this study 4aAA6. Sound absorption of Helmholtz resonators included a neck informs the decision-making of designers and facilities management for extension built in surface panel. Shinsuke Nakanishi (Dept. of Eng., Hiro- shima Int. Univ., 5-1-1, Hiro-koshingai, Kure 737-0112, Japan, s-nakani@ upgrades and future design projects. it.hirokoku-u.ac.jp) 10:45 Acoustic resonant absorber like a perforated panel or a Helmholtz reso- 4aAA9. Subjective acoustical quality in healthcare office facilities. Mur- nator can be tuned at a low frequency by extending its neck or enlarging ray Hodgson (UBC, 2206 East Mall, Vancouver, BC V6T1Z3, Canada, mur- cavity volume. However, a total size of the resonators is often quite large [email protected]) when the neck or the cavity is simply extended for tuning at a low fre- quency. Previous researchers have studied Helmholtz resonator shortened in Health-care facilities include many non-clinical office spaces for admin- its size by subsided neck into back air cavity, and confirm that this resonator istrative staff; the role of acoustics in these spaces has been underexplored. is tuned at low frequency without a deep cavity. The author has studied the This paper discusses the acoustical part of a study of indoor environmental effects of a winding built-in neck extension to sound absorption of perfo- quality (IEQ) in 17 healthcare office facilities. A subjective survey assessed rated panels, which shows same effects as the subsided neck into back cav- office worker perceptions of their environments in general, and satisfaction ity. This study obtains sound absorption coefficient by measuring surface with the acoustics. Self-reported productivity, well-being, and health out- acoustic impedance at Helmholtz resonator, and discusses sound absorption comes were also captured. Satisfaction was lower with acoustics than with of the resonator included various neck extensions built in a surface panel. other aspects of IEQ. Satisfaction results were related to room type (e.g., Discussions in this paper focus effects of path length, patterns, or number of open plan vs. shared vs. private office) and the absence or presence of a turns of the winding neck extension and cavity volume to the sound absorp- sound-masking system. Acoustics was the most important aspect of IEQ in tion of the Helmholtz resonator. predicting occupant satisfaction and well-being. Regression models were developed to predict workplace satisfaction, well-being, and job satisfaction 10:00–10:15 Break from survey responses. Results of physical acoustical measurements showed very low correlations with subjective responses. The knowledge gained 10:15 from this study informs the decision-making of designers and facilities man- agement for upgrades and future design projects.
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