Sound Level Meters

Sound Level Meters

Sound level meters measure sound pressure/intensity over the human hearing range of 10 Hz to 20,000 Hz. Measurements are reported as “unfiltered” or “unweighted”,  filtered to approximate human hearing response over 10-20,000 Hz frequency range, or “A” weighted, and “C” weighted. “A” weighting is commonly used by most regulatory agencies for sound measurements.  Sound is measured in Decibels, or dB. The dB scale is logarithmic. Measurements may also be reported with “fast” or “slow “response”, which refers the response of the meter, with slow response most commonly used. Slow response ignores or greatly reduces the measured dB of a very short pulse, which though quite loud is of extremely short duration, a pulse such as a gun shot or door slam. When set to fast response the meter will register the very short, loud sounds such as a gun shot or door slam. Meters are available that show only the instantaneous dB or which average the dB over the time of the measurement, or Integrating Meters. There are also Octave band, and 1/3 Octave band meters which measure the dB over sequential portions of the sound spectrum. Sound meters are also available for reading instantaneous as well as integrated dB. And not to be ignored are data logging instruments.

The response characteristics of the microphones used to measure sound levels may be without performance criteria, such as the analog sound level 840005, or classed as meeting ANSI S1.4 and IEC61672 criteria for Type 1 or Type 2 response; type 1 is precision, type 2 general purpose. For purpose of this discussion Class 1 tolerance is ±0.7dB, Class 2 ±1.0 dB.

Some common reference sound levels are:

Quiet outdoor environment ~40 dB

Quiet conversation between friends ~65 dB

Jet engine ~110-115 dB

A simple rule of thumb, and it is no more than that, a guidance, is a dB reading of about 85 dB over several minutes or machine cycles warrants further investigation with a Sound Dosimeter to quantify the sound dose and the need for formal hearing conservation measures.

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