What is A Sound Level Meter?
Sound level meters measure sound pressure level and are commonly used in pollution studies for the quantification of almost any noise, but especially for industrial, environmental and aircraft noise. However, the reading given by a sound level meter does not correlate well to human-perceived loudness; for this a loudness meter is needed. The current International standard for sound level meter performance is IEC 61672:2003 and this mandates the inclusion of an A-frequency-weighting filter and also describes other frequency weightings of C and Z (zero) frequency weightings. The older B and D frequency-weightings are now obsolete and are no longer described in the standard.
How does A Sound Level Meter work?
Sound is an oscillation in the air. It travels as waves of pressure increasing and decreasing pressure. The strength of the pressure waves determines the volume of the sound. Sound volume is usually measured in decibels (dB). Decibels don't increase linearly, but logarithmically. So if one sound is 10 decibels stronger than another, it actually exerts 10 times as much pressure. The sound of a jet engine at 110 decibels is actually 10 million times as strong as the sound of leaves rustling. Loud sounds actually contain so much energy that they can damage the ear drums. Sound level meters are usually used to make sure sounds are kept at a safe level.
Decibel meters use microphones, just like sound recorders. The microphone contains a grill or screen, which protects a movable cartridge or membrane. When the pressure waves from a sound collide with the membrane, they move it back and forth. This causes the membrane to create an electric current. The more the membrane moves, the stronger the current it creates. The sound level meter measures the strength of the current, and turns it into a number indicating the volume of the sound.
Recording and Processing the Information
There are some sounds which are so loud that even being exposed to them for a few seconds can damage the hearing. For many sounds, however, the issue of safe exposure is a little more complicated. These sounds fall into an intermediate range; they are safe to hear for a short period of time, but can damage your hearing if you are constantly exposed to them. Therefore, sound meters have to log, or record sound levels. They take samples of the sound over a period of hours or days, and record them. They can use these samples to calculate an average volume. They can also store sound level peaks. that way, the meters can gauge whether the sound level ever gets high enough to be an immediate danger and whether its average is high enough to damage hearing over the long run.
A sound level meter is used to measure the sound pressure level; these devices are primarily used to determine noise pollution levels. Different model sound level meters have different methods of operation though most have more or less the same functionality. They are generally small (hand held), portable and use batteries. The sound level meter will have a microphone, LCD or analog display and function buttons. The amount of function buttons relates to the complexity of the unit but most have a power, hold and minimum and maximum function. Range, time and weighting are other common function buttons.
The accuracy of a sound level meter is entirely dependent upon its calibration. Improperly calibrated units will give inaccurate readouts, and are basically useless. Be sure to calibrate your sound level meter before and after each measurement session by situating an acoustic calibrator, like a sound level calibrator or Piston Phone, above the sound level meter's microphone. Other Models… Need More Information:
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