Novel method of sound barrier measurement of porous and nonporous materials

Noise is an unwanted sound which creates the pollution and adverse effects on individual. One of the simple ways to reduce the noise is to place the acoustic material in the path between the source and the receiver so that sound waves get either absorbed or blocked while reaching towards the receiver. There are various techniques available to measure sound absorption or sound barrier (blocking) caused by the acoustic material. However these techniques are also associated with certain limitations. Our objective was to design and fabricate simple technique to measure sound barrier which overcomes these limitations and allows larger sample size and random scatter of sound wave to accurately predict actual field measurements. A sound source (i.e. a speaker) and a microphone, placed in different pipes separated by sample in between, were used for the measurement of sound barrier property of porous materials (nonwovens, woven fabric, and foam), nonporous materials (rubber, cardboard) and their composite structures at four different frequencies 250 Hz, 500 Hz, 1,000 Hz, and 2000 Hz. Different set of readings were taken in absence and presence of the sample by measuring the transmitted sound across the sample.