Index of content:
Volume 126, Issue 3, September 2009
- NOISE: ITS EFFECTS AND CONTROL 
126(2009); http://dx.doi.org/10.1121/1.3180695View Description Hide Description
The development and application of a procedure for the assessment of low frequency noise (LFN) complaints are described. The development of the assessment method included laboratory tests addressing low frequency hearing threshold and the effect on acceptability of fluctuation, and field measurements complemented with interview-based questionnaires. Environmental health departments then conducted a series of six trials with genuine “live” LFN complaints to test the workability and usefulness of the procedure. The procedure includes guidance notes and a pro-forma report with step-by-step instructions. It does not provide a prescriptive indicator of nuisance but rather gives a systematic procedure to help environmental health practitioners to form their own opinion. Examples of field measurements and application of the procedure are presented. The procedure and examples are likely to be of particular interest to environmental health practitioners involved in the assessment of LFN complaints.
126(2009); http://dx.doi.org/10.1121/1.3183416View Description Hide Description
The effect of leakage in Helmholtz resonators has been investigated in this predominantly experimental study combined with a computational effort. A prototype has been built with varying levels of intentional leakage due to holes in the baffle and gaps between the baffle and the housing. The transmission loss is then measured with different combinations of holes and/or gaps. Such openings, even though their cross-sectional areas are small, are found to have a significant impact on transmission loss. The effect of holes versus gaps is also compared as a function of the leakage area. The present study illustrates the critical need to account for such leakages at the design stage for the proper tuning of these resonators.
Bicylindrical model of Herschel–Quincke tube-duct system: Theory and comparison with experiment and finite element method126(2009); http://dx.doi.org/10.1121/1.3159370View Description Hide Description
An analytical three dimensional bicylindrical model is developed in order to take into account the effects of the saddle-shaped area for the interface of a -Herschel–Quincke tube system with the main duct. Results for the scattering matrix of this system deduced from this model are compared, in the plane wave frequency domain, versus experimental and numerical data and a one dimensional model with and without tube length correction. The results are performed with a two-Herschel–Quincke tube configuration having the same diameter as the main duct. In spite of strong assumptions on the acoustic continuity conditions at the interfaces, this model is shown to improve the nonperiodic amplitude variations and the frequency localization of the minima of the transmission and reflection coefficients with respect to one dimensional model with length correction and a three dimensional model.
Modeling subjective evaluation of soundscape quality in urban open spaces: An artificial neural network approach126(2009); http://dx.doi.org/10.1121/1.3183377View Description Hide Description
This research aims to explore the feasibility of using computer-based models to predict the soundscape quality evaluation of potential users in urban open spaces at the design stage. With the data from large scale field surveys in 19 urban open spaces across Europe and China, the importance of various physical, behavioral, social, demographical, and psychological factors for the soundscape evaluation has been statistically analyzed.Artificial neural network (ANN) models have then been explored at three levels. It has been shown that for both subjective sound level and acoustic comfort evaluation, a general model for all the case study sites is less feasible due to the complex physical and social environments in urban open spaces; models based on individual case study sites perform well but the application range is limited; and specific models for certain types of location/function would be reliable and practical. The performance of acoustic comfort models is considerably better than that of sound level models. Based on the ANN models,soundscape quality maps can be produced and this has been demonstrated with an example.