Factors Influencing Acoustic Performance of Sound Absorptive Materials

Abstract

Today much importance is given to the acoustical environment. Noise control and its principles play an important role in creating an acoustically pleasing environment. This can be achieved when the intensity of sound is brought down to a level that is not harmful to human ears. Achieving a pleasing environment can be obtained by using various techniques that employ different materials. One such technique is by absorbing the sound. Fibrous, porous and other kinds of materials have been widely accepted as sound absorptive materials. This paper review and describes how the physical prosperities of materials like fiber type, fiber size, material thickness, density, airflow resistance and porosity can change the absorption behavior. The effect of surface impedance, placement / position of sound absorptive and compression, on sound absorption behavior of materials was also considered. The sound absorption of different fibrous materials was experimentally tested. The results shows the relationship between the sound absorption and airflow resistance, material thickness, air gap and attachment film. Higher airflow resistance always gives better sound absorption values but for airflow resistance higher than 1000 the sound absorption have less values because difficulty movements of sound wave through the materials. The creation of air gap, 5mm, 10 mm behind the absorptive material increases sound absorption coefficient values in mid and higher frequencies. There is not much difference seen between 5 mm air gap sample and 10 mm air gap sample. Moreover, maxima peak for different air gap is different (higher the air gap distance, maxima peak shift towards lower frequency