Home Cinema Acoustic Panels - October 12th, 2008

Of considerable importance to the acoustics of a home cinema room are the loss mechanisms which reduce the energy of sound waves when they are reflected from walls as well as their free propagation in the air. They influence the strengths of the direct sound and of all reflected components and therefore all acoustical properties of the home cinema room.

With the proper choice of materials used in construction and finish, the absorption and hence the sound transmission in a dedicated home cinema installation can be substantially influenced in a desired way; furthermore, a particular frequency dependence can be given to it by the home cinema designer.  

By using porous absorbers as wall treatments, like acoustic panels, we can easily treat some acoustic problems. These panels range from standard well-known materials, such as mineral wool and fibre glass. When sound propagates in small spaces, such as the acoustic panel’s interconnected pores, channels and voids connected with the air outside, energy is lost. The pressure fluctuations associated with the external sound field give rise to alternating air flows in the pores and channels, the walls of which will be filled more or less by the lossy layer, so to speak. The consequence is that a significant amount of mechanical energy is withdrawn from the external sound field and is converted into heat.

Air is a viscous fluid, and consequently sound energy is dissipated via friction with the pore walls of the acoustic panel. As well as viscous effects, there will be losses due to thermal conduction. As the acoustic panel’s thickness increases, the absorption at low frequency usually increases.

In order to create significant absorption with an acoustic panel in a home cinema installation, it needs to be placed somewhere where the particle velocity is high. The particle velocity close to the home cinema’s walls is small, so placing acoustic panels there, does not generate much absorption. This is why thicker wall treatments are needed for a more effective absorption.

The need for significant thickness of acoustic panels in a home cinema installation makes panels not so useful for treating low frequencies. In dedicated home cinema installations, combination of acoustic panels and resonant absorption will ensure a broader absorption across the frequencies.

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Filed under: Technical Articles — admin @ 1:09 am

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