Volume 110, Issue 2, August 2001
Index of content:
- NOISE: ITS EFFECTS AND CONTROL 
110(2001); http://dx.doi.org/10.1121/1.1385900View Description Hide Description
The Helmholtz integral equation formulation is used to produce the solution for the acoustic field reflected from a finite, thin, poroelastic plate in a rigid baffle with simply supported edges. The acoustic properties of the porous material are predicted using the effective fluid assumption. The solutions for the displacement of the plate and for the loading acoustic pressures are given in the form of the sine transform. The sine transform coefficients are obtained from the solution of a system of linear equations resulting from three integral Helmholtz formulations which relate the displacement of the plate and the acoustic pressures on the front and on the back of the plate. The effect of an air gap behind the plate in the front of a rigid wall is also considered. A parametric study is performed to predict the effect of variations in the parameters of the poroelastic plate. It is shown that thin, light, poroelastic plates can provide high values of the acoustic absorption even for low frequency sound. This effect can be exploited to design compact noise control systems with improved acoustic performance.
110(2001); http://dx.doi.org/10.1121/1.1381539View Description Hide Description
To assess the acoustical performance of noise screens in the presence of an arbitrary sound speed profile, a numerical scheme based on a combination of the boundary integral and fast field program methods is developed. The Green’s function required in the boundary integral is evaluated by a fast field formulation. The procedure is validated by comparing its predictions with other numerical results for simple cases and with measurements for indoor modelexperiments simulating downward refracting conditions. It is predicted that the performance of a noise screen placed 50 m from the source is reduced considerably by moderate downwind conditions.
110(2001); http://dx.doi.org/10.1121/1.1387095View Description Hide Description
The present study evaluates the effectiveness of active sound transmission control inside an enclosure using a purely acoustic source under the potential energy, squared pressure, and energy density control algorithms. Full coupling between a flexible boundary wall and the interior acoustic cavity is considered. Formulas based on the impedance-mobility approach are developed for the active control of sound transmission with the energy density control algorithm. The resultant total acoustic potential energy attenuation and sound fields under the three control algorithms are compared. Global amplification of the sound level with localized quiet zones under the squared pressure control is observed. This adverse effect can be removed by using the energy density control. It is also shown that the energy density control provides a more uniform control of sound field. Better performance of global and local control of sound field using the squared pressure and energy density controls can be achieved by locating the error sensors at the peak quiet zones and the areas of peak energy density attenuation, respectively, obtained under potential energy control.
General scales of community reaction to noise (dissatisfaction and perceived affectedness) are more reliable than scales of annoyance110(2001); http://dx.doi.org/10.1121/1.1385178View Description Hide Description
General measures of reaction to noise, which assess the respondent's perceived affectedness or dissatisfaction, appear to be more valid and internally consistent than more narrow measures, such as specific assessment of noise annoyance. However, the test–retest reliability of general and specific measures has yet to be compared. As a part of the large-scale Sydney Airport Health Study, 97 respondents participated in the same interview twice, several weeks apart. Test–retest reliabilities were found to be significant for two general questions and three specific “annoyance” questions. The general measures were significantly more valid for four of the six correlations (with activity disturbance), and more stable than the annoyance scales for five of the six possible test–retest comparisons. Amongst 1015 respondents at Time 1, the questions regarding general reaction were more internally consistent than the questions regarding annoyance. Taken together, these data indicate that general measures of reaction to noise have superior psychometric properties (validity, internal consistency, and stability) compared with measures of specific reactions such as annoyance.