Experimental and Numerical Investigation of Room Sound Fields

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Acoustical environments in rooms have direct effects on the health, comfort, productivity and enjoyment of the occupants. The direct and indirect socio-economic costs of such problems can be enormous. The proposed research will develop improved tools for predicting and controlling sound, and for the accurate acoustical characterization of room surfaces and materials. Acoustical environments can be designed and controlled. This is often done retroactively, once problems are experienced, at great expense. Optimization of the acoustical environment at the design stage is cost-effective. Retroactive control measures must be introduced in a cost-effective manner. Noise control traditionally involves passive methods; the future of noise control must involve active methods. Room sound-field prediction and acoustical design rely on reliable test data. Testing governed by standards and performed in standardized test facilities must be valid. Reverberation test rooms - used to measure surface absorption, transmission and scattering - have been questioned, and require further investigation and refinement. Room design requires accurate prediction models and associated input data. How real room surfaces absorb and scatter sound is still not well understood, though we know it has a huge effect. Work proposed here aims to resolve this by developing and applying in-situ techniques to obtain reliable data. The proposed research will investigate fundamental aspects of room sound fields experimentally and numerically. Numerical methods will be used to predict diffuse sound fields and develop improved criteria for the design of reverberation rooms. In preparation for applying active noise control to 'fitted' workrooms, sound scattering of pressure fields by obstacles and their effects in rooms will be investigated experimentally. Existing measurement methods will be extended to rooms, and inverse methods applied, to characterize surfaces in situ. A new room-acoustical parameter and associated design criteria will be developed and tested.