I first heard about sound level meters and noise dosimeters a few years ago when I worked I worked in a garment factory. Sound level meters and noise dosemeters are used any place where there is a lot of noise and it is necessary to have some kind of measurements and controls in place.
Being exposed to loud noises for a brief period of time usually does no harm, but imagine having to suffer it hour upon hour, day after day. If noise is a problem to you, the first thing you need to do is measure how loud it is so you can take effective steps to reduce it. Making precise measurements of noise used to be quite a tricky business, but now there are automated, electronic sound-level meters that do the job for you.
What makes one sound louder than another?
How loud a sound seems to be depends on who’s listening. However, what makes one sound seem louder than another is the amount of energy that the source of the sound is pumping towards the listener in the form of pressure variations in the air. That’s the intensity of the sound and it’s an objective thing–something we can easily measure and agree on.
Meters that measure sound levels work by calculating the pressure of the sound waves traveling through the air from a source of noise. That’s why you’ll sometimes see them referred to as sound pressure level (SPL) meters. Devices like this give a measurement of sound intensity in units called decibels, a scale first devised by telephone pioneer Alexander Graham Bell.
Sound level meters assess sound pressure level, commonly used in noise pollution studies for the quantification of different kinds of noise, especially for industrial, environmental and aircraft noise. However, the reading from a sound level meter does not correlate well to human-perceived loudness, which is better measured by a loudness meter. The current international standard that specifies sound level meter functionality and performance is the IEC 61672-1:2013.
IEC standards divide sound level meters into two “classes”. Sound level meters of the two classes have the same functionality, but different tolerances for error. Sound level meters Class 1 have a wider frequency range and a tighter tolerance than the cheaper sound level meters Class 2 units. This applies to both the sound level meter itself as well as the associated calibrator. Most national standards permit the use of “at least a Class 2 instrument”. For many measurements, there is little practical point in using a Class 1 unit; these are best employed for research and law enforcement.
The factory in which I used to work was very noisy on the actual manufacturing floor due to not only the noise of the machines but also due to the level of talk, music and other sounds. I was lucky enough to have a side room in which to work where the noise levels were much lower, something which was obvious even without the use of sound level meters and noise dosimeters.
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