An acoustical technique for determining the loss factor of solid materials

A technique is presented here for evaluating the loss factor of a solid material element. This technique is commonly used in room acoustics to evaluate the reverberation time (RT) of rooms, and is therefore reviewed in this paper for applications in solid materials. The reverberation time is a quantity that describes the rate of decay of the sound level in the room, and is inversely proportional to the amount of sound absorption in the room. The loss factor is a measure of the proportion of vibrational energy that is dissipated during one cycle of vibration. Hence, interest is focused in this study on the damping characteristics of the material in terms of the loss factor, which is inversely proportional to RT. The reverberation time may be assessed relatively easily and rapidly from the impulse response of the test specimen as measured with the help of a smart technique. The example of a wood beam-like specimen with artificial defects in the form of voids is presented.