Acoustic Performance of Silica Aerogel Composites

Acoustics is the interdisciplinary science that deals with the study of mechanical waves and vibrations in the three states of matter with the aid of a medium to propagate. Sound is often described as audible waves and vibrations in the spectrum of 20-20 kHz (Dowling and Williams 1983). The sound source creates vibrations in the surrounding medium. As the source continues to vibrate the medium, the vibrations propagate away from the source at the speed of sound, thus forming the sound wave. At a fixed distance from the source, the pressure, velocity, and displacement of the medium vary in time. At an instant in time, the pressure, velocity, and displacement vary in space. The particles of the medium do not travel with the sound wave but the relative displacement or vibration from the fixed positions that result in wave propagation (Dowling and Williams 1983). These waves can be reflected, refracted, or attenuated by the medium. 

B K Generator Module 3107 with 4-channel microphone model 3028 

Silica aerogel granules, being highly porous sohds, have the potential to be a sound absorbent material. Sound absorbers are usually characterized by surface impedance and absorption coefficient. A one-dimensional plane wave in the tube is assumed to be (Sung Soo et al. 2008). The total acoustic pressures about 

Equation (7.3) is the reflection coefficient for the two microphone transfer function method. When the specimen is backed by a rigid back waU, there wiU be no transmitted waves and thus by conservation of energy, all the incident waves are reflected and absorbed. Thus the absorption coefficient ( i), can be expressed as in 

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Acoustic Performance of Silica Aerogel Composites GSA-SDS [20/80/0.56] Size 1.7mm... 

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