Acoustics Expert Witness On Sound Insulation

Acoustic expert witness Angelo J. Campanella, P.E., Ph.D. FASAA explains the difference between sound absorption & sound insulation:

There is often confusion between sound insulation and sound absorption.

Sound is absorbed when it encounters a material which will convert some or all of it into heat, or which allows it to pass through not to return. For this reason good sound absorbers do not of themselves make good sound insulators. Sound insulators rarely absorb sound. Sound absorbers contribute little to sound insulation. They are treated separately in sound control design.

Sound insulation prevents sound from traveling from one place to another, such as between apartments in a building, or to reduce unwanted external noise inside a concert hall. Heavy materials like concrete are the most effective materials for sound insulation – doubling the mass per unit area of a wall will improve its insulation by about 6dB. It is possible to achieve good insulation over most of the audio frequency range with less mass by instead using a double leaf partition (two independent walls separated by an air gap filed with a sound absorber).

Mr. Campanella is principal of Campanella Associates,