The commonly used noise measuring equipments are:
(i) Sound Level Meter :
It consists of a non-directional microphone coupled to an amplifier to transform sound wave (sound pressure level) to a proportional electric signal.
It measures the RMS value of noise and can also be calibrated to measure the peak level of sound. The sound level meter (IEC 123) is cheap to do rough estimation of high and low frequency sound level, whereas (IEC 179) are expensive but have high degree of accuracy.
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(ii) Cassette Recorder :
It is cheaper and used to store noise for rough evaluation. It is used for digital recording of sound pressure level (SPL) for computer evaluation.
(iii) Magnetic Tape Recorder :
It is a costly instrument compared to cassette recorder. Such recorder is directly fed through sound level meter or microphone. It records the noise more accurately and stores it for better evaluation.
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(iv) Pen Recorder:
Pen recorder can be fed directly or from sound level meter or magnetic tape recordings. Pen recorder can do continuous recording of sound pressure level (SPL), as well as discontinuous recording of instantaneous sound pressure level (SPL) from the received noise.
(v) Noise Average Meter (L Meters):
Noise average meter measures sound levels with great accuracy. Noise average meter is fed directly or from magnetic tape recordings.
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(vi) Noise Analyzer:
This instrument is fed directly or from magnetic tape recordings. It consists essentially of a sound level meter (IEC 179), which feeds a noise average meter. It can provide digital display also.
Some other commonly used instruments are impulse noise meters, vibration meters, noise limit indicators, etc.