The Fiber Vibration Sound Absorption Theory 2007-01-2188
Fibrous materials had been used as sound absorption materials for over one century. The current sound absorption theory is still the Rayleigh model. But it not agrees with the practice even though it had been studied for over 100 years. Based of Rayleigh model, Zwikker and Kosten established the theory of acoustical effective density and the effective bulk modulus which is also the popular theory in acoustics literature to explain the sound absorption characteristics of fibrous materials. However, because of the complexity of these expressions, it is difficult to obtain physical insight into the acoustic behavior of the porous materials and to determine the dominant mechanism for sound absorption for a given material at a given frequency. Alternatively there are very simple expressions.
A new theory was put forward that fibrous material absorb the sound by the fiber's vibration. This theory have been justified by the equation obtained from the vibration analyzing as well as the empirical sound absorption formula of fibrous material in another paper of the author.