Volume 127, Issue 2, February 2010
Index of content:
- ARCHITECTURAL ACOUSTICS 
127(2010); http://dx.doi.org/10.1121/1.3277220View Description Hide Description
Speech levels were measured in a large number of meetings and meeting rooms to better understand their influence on the speech privacy of closed meeting rooms. The effects of room size and number of occupants on average speech levels, for meetings with and without sound amplification, were investigated. The characteristics of the statistical variations of speech levels were determined in terms of speech levels measured over intervals at locations inside, but near the periphery of the meeting rooms. A procedure for predicting the probability of speech being audible or intelligible at points outside meeting rooms is proposed. It is based on the statistics of meeting room speech levels, in combination with the sound insulation characteristics of the room and the ambient noise levels at locations outside the room.
127(2010); http://dx.doi.org/10.1121/1.3278605View Description Hide Description
Spatial impression is an important acoustic quality of concert halls. An accepted objective measure for spatial impression is the interaural cross-correlation (IACC) coefficient. Recently, spherical microphone arrays have been studied for room acoustics analysis and music recordings. This study presents a theoretical formulation for the computation of IACC using spherical-harmonics representations of the sound field, as measured by spherical microphone arrays, and spherical-harmonics representation of head-related transfer functions (HRTFs), taken from HRTF databases. As spherical microphone arrays typically use a finite number of microphones, they may not be able to capture the complete spatial information in a sound field. Therefore, the effect of limited spherical-harmonics order on the accuracy of IACC approximation using the proposed method is studied using simulated and measured data. The method presented in this paper can be further used to study the effect of limited spatial information on the spatial perception of sound fields.
127(2010); http://dx.doi.org/10.1121/1.3273885View Description Hide Description
The sound transmission characteristics of an aluminum panel and two composite sandwich panels were investigated by using two boundary element analyses. The effect of air loading on the structural behavior of the panels is included in one boundary element analysis, by using a light-fluid approximation for the eigenmode series to evaluate the structural response. In the other boundary element analysis, the air loading is treated as an added mass. The effect of the modal energy loss factor on the sound transmission loss of the panels was investigated. Both boundary element analyses were used to study the sound transmission loss of symmetric sandwich panels excited by a random incidence acoustic field. A classical wave impedance analysis was also used to make sound transmission loss predictions for the two foam-filled honeycomb sandwich panels. Comparisons between predictions of sound transmission loss for the two foam-filled honeycomb sandwich panels excited by a random incidence acoustic field obtained from the wave impedance analysis, the two boundary element analyses, and experimental measurements are presented.
The improvement of a simple theoretical model for the prediction of the sound insulation of double leaf walls127(2010); http://dx.doi.org/10.1121/1.3273889View Description Hide Description
This paper presents a revised theory for predicting the sound insulation of double leaf cavity walls that removes an approximation, which is usually made when deriving the sound insulation of a double leaf cavity wall above the critical frequencies of the wall leaves due to the airborne transmission across the wall cavity. This revised theory is also used as a correction below the critical frequencies of the wall leaves instead of a correction due to Sewell [(1970). J. Sound Vib.12, 21–32]. It is found necessary to include the “stud” borne transmission of the window frames when modeling wide air gap double glazed windows. A minimum value of stud transmission is introduced for use with resilient connections such as steel studs. Empirical equations are derived for predicting the effective sound absorption coefficient of wall cavities without sound absorbing material. The theory is compared with experimental results for double glazed windows and gypsum plasterboard cavity walls with and without sound absorbing material in their cavities. The overall mean, standard deviation, maximum, and minimum of the differences between experiment and theory are −0.6 dB, 3.1 dB, 10.9 dB at 1250 Hz, and −14.9 dB at 160 Hz, respectively.