Downloaded from orbit.dtu.dk on: Sep 26, 2021 Free-field reciprocity calibration of laboratory standard (LS) microphones using a time selective technique Rasmussen, Knud; Barrera Figueroa, Salvador Published in: Journal of the Acoustical Society of America Publication date: 2006 Document Version Publisher's PDF, also known as Version of record Link back to DTU Orbit Citation (APA): Rasmussen, K., & Barrera Figueroa, S. (2006). Free-field reciprocity calibration of laboratory standard (LS) microphones using a time selective technique. In Journal of the Acoustical Society of America (Vol. 120) General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. Users may download and print one copy of any publication from the public portal for the purpose of private study or research. You may not further distribute the material or use it for any profit-making activity or commercial gain You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. FRIDAY MORNING, 1 DECEMBER 2006 LANAI ROOM, 7:30 TO 11:55 A.M. Session 4aAA Architectural Acoustics: Measurement of Room Acoustics I Fumiaki Satoh, Cochair Chiba Inst. of Technology, Tsudanuma 2-17-1 Narashino-shi, Chiba 275-0016, Japan Boaz Rafaely, Cochair Ben Gurion Univ., Electrical and Computer Engineering Dept., 84105, Beer Sheva, Israel Chair’s Introduction—7:30 Invited Papers 7:35 4aAA1. Warped-time-stretched pulse: An acoustic test signal robust against ambient noise. Masanori Morise, Toshio Irino, Hideki Banno, and Hideki Kawahara ͑Wakayama Univ., 930, Sakaedani, Wakayama, 640-8510, Japan, [email protected]͒ A new acoustic measurement signal that is a hybrid signal of time-stretched pulse ͑TSP͒, or lin-TSP, and logarithmic TSP ͑log-TSP͒ is proposed. The signal, referred to as warped-TSP ͓Morise et al., IEICE Trans. Fundamentals, A, J89-A͑1͒, 7–14 ͑2006͔͒, has a single parameter to adjust for better measurements in accordance with ambient noise conditions. It also provides a means to eliminate harmonic distortions produced mainly by loudspeaker systems. In this lecture, the definition and features of the warped-TSP in comparison with the lin-TSP and log-TSP are introduced. The following were shown: ͑1͒ the relationship between the parameters, the amplitude frequency characteristics, and the effect on the harmonic distortion components; ͑2͒ a method to select the optimal parameters of the warped-TSP for a specific measuring environment; and ͑3͒ the experimental results for a series of impulse response measurements under different ambient noise conditions. Those results show that the proposed method outperformed the lin-TSP and log-TSP under all conditions in terms of SNR of the measured impulse response. ͓This research was supported partly by grants-in-aid for scientific research ͑15300061 and 15650032͒ and a grant from the Faculty of Systems Engineering at Wakayama University.͔ 7:55 4aAA2. Simultaneous estimation of reverberation times and their uncertainties from room impulse responses using a single-measurement procedure. Ning Xiang and Tomislav Jasa ͑Grad. Program in Architecture Acoust., and Dept. of Elec., Comput., and Systems Eng., Rensselaer Polyt. Inst, Troy, NY 12180͒ Accurate measurements of reverberation times are of fundamental importance in room acoustics. A number of test procedures for characterizing acoustics in performing arts venues, quantifying acoustic properties of materials in chamber measurements, rely on experimental determination of reverberation times. In addition, decay-time estimation in acoustically coupled spaces has been found to be very demanding. Our recent work has demonstrated that model-based Bayesian approaches ͓Xiang et al., J. Acoust. Soc. Am. 110, 1415–1424 ͑2001͒; 113, 2685–2697 ͑2003͒; 117, 3705–3715 ͑2005͔͒ can be very useful for such analysis in architectural acoustics measurements. This paper discusses the recent development of probabilistic tools for estimating both reverberation ͑decay͒ times and their uncertainties within Bayesian framework. This work shows that Bayesian probabilistic inference can be used as a useful tool for sound energy decay analysis in both single-space halls and coupled spaces. Bayesian decay analysis simultaneously 4a FRI. AM provides architectural acousticians with reverberation times, diverse decay times, related derivations, and interdependencies to quan- tify uncertainties of the estimation from a single measurement of room impulse responses followed by Schroeder backward integra- tions. 8:15 4aAA3. Permissible number of synchronous averaging times to obtain reverberation time from impulse response under time-variance conditions. Fumiaki Satoh, Yukiteru Hayashi ͑Chiba Inst. of Technol., Tsudanuma 2-17-1, Narashino-shi, Chiba, 275-0016, Japan͒, Shinichi Sakamoto ͑Univ. of Tokyo, Meguro-ku, Tokyo, 153-8505, Japan͒, and Hideki Tachibana ͑Chiba Inst. of Technol., Narashino-shi, Chiba, 275-0016, Japan͒ In the measurement of room impulse response, the synchronous averaging technique and such new methods as the MLS and the swept-sine methods are being widely used to improve the signal-to-noise ratio. In actual measurement conditions, however, the air in a room is continuously moving and the temperature is changing to some degree. The measured value of the reverberation time in such a room tends to be shorter at higher frequencies when applying the synchronous averaging. Therefore, the assumption of a time invariant has to be carefully considered, and, on this point, some research has been conducted to date. We also have reported various research results concerning the impulse response measurement under the time-variance conditions. In this paper, the permissible number of synchronous averaging times for reverberation measurement is studied through some field experiments. In each field, many 3223 J. Acoust. Soc. Am., Vol. 120, No. 5, Pt. 2, November 2006 Fourth Joint Meeting: ASA and ASJ 3223 time impulse response measurements were taken between a fixed pair of sound source and receiving positions by the swept-sine method, without averaging. After the measurements, the characteristics and the extent of the time-variance under measuring were estimated by a short-term running cross-correlation function between each impulse response. The influence of the time variance on the synchronous averaging result was studied based on the estimated time variance. 8:35 4aAA4. Selection of receiving positions suitable for evaluating acoustical parameters. Taeko Akama, Hisaharu Suzuki, and Akira Omoto ͑Omoto Lab., Dept. of Acoust. Design, Faculty of Design, Kyushu Univ., Shiobaru 4-9-1, Minami, Fukuoka 811-8540, Japan͒ Many physical parameters show characteristics of large sound fields such as concert halls. Some of them are adopted in the Annex of ISO 3382. That definition is clearly provided in ISO. However, practical measurement methods for them remain obscure. Our research is intended to examine an effective selection method of receiving positions based on the distribution of acoustical parameters in a real field. For that purpose, impulse responses are measured at more than 1400 seat positions to elucidate the distribution of acoustical parameters in an existing concert hall. The acoustical parameters, which are reverberation time, early decay time, clarity, and center time at each seat, are then calculated for 500-Hz, 1-kHz, and 2-kHz octave bands. The distributions of reverberation time are quite even at all seats. However, the distributions of other parameters show symmetrical patterns at 500 Hz. At 1 and 2 kHz frequencies, the distributions show asymmetrical patterns in this hall. Based on the results obtained in this study, an effective method to select the receiving position can be proposed. 8:55 4aAA5. Hybrid measurement method in room acoustics using dodecahedron speakers and a subwoofer. Hideo Miyazaki ͑Ctr. for Adv. Sound Technologies, Yamaha Corp., 203 Matsunokijima, Iwata, Shizuoka 438-0192, [email protected]͒ A dodecahedron speaker is usually utilized for measurement in room acoustics under the hypothesis of omni directional point source. But generally speakers used for a dodecahedron speaker cannot playback low-frequency sound such as under 100 Hz, which is important especially for auralization, while the one constructed of units with large diameter to support low-frequency sounds cannot be considered as an omni-directional speaker in high frequencies. To meet these requirements, a hybrid system combining a dodeca- hedron speaker and a subwoofer has been developed and actually used for measurements of impulse responses in acoustical design of concert halls. The summary of this method will be presented. The feasibility of this method will be also discussed while evaluating the measurement results in concert halls by changing measurement conditions such as speaker locations and comparing these results with those of conventional methods. 9:15 4aAA6. The perception of apparent source width and its dependence on frequency and loudness. Ingo B. Witew and Johannes A. Buechler ͑Inst. of Tech. Acoust., RWTH Aachen Univ., Templergraben 55, 52066 Aachen, Germany͒ While it is widely accepted that