Acoustic testing

Laboratory testing

A number of acoustic test houses exist throughout the UK such as the SRL (Sound Research Laboratories), BRE (British Research Establishment), Salford University, etc.  Tests carried out in test houses are typically used for research purposes, but also to measure performance figures for equipment, structures (walls, floors roofs), machines, sound absorption, etc.Tests carried out in laboratories are done so in 'ideal' situation, where the background noise and flanking paths are carefully controlled. 

Field-testing

Field-testing is typically carried out to determining the level of noise generated by noisy machines, noisy neighbours, train/ air traffic/ traffic noise etc.

Acoustic equipment commonly used:

• Sound level meter, 
• Piston phone for calibration, (calibration is done by means of a source of known noise level, such as a piston phone.  The piston phone fits over the microphone on the sound level meter and produces a note of 250Hz at 124dB.  Calibration helps to insure that accurate levels dB levels are measured).
• Filters, (filters are used to select appropriate band of frequencies, filters working to one octave or third-octave bandwidths are most common for building acoustics).
• Switchbox, (control of noise source, on/ off).
• Microphones beat frequency oscillator or sine random generator, (noise source).
• Amplifier
• Tapping machine

Software is available to process the measurements taken and can be printed out in a spread sheet or similar.

The manufacture or an accredited test institution at least once a year must calibrate acoustic equipment used.

Why do we need to test? To be able to compare performance figures and to insure that requirements are met.  Also in disputes and when dealing with noise complaints it is necessary to evaluate figures.