A sound level meter (SLM) is an electronic device used to measure the sound pressure levels in a given area. SLMs are often used to determine if an environment is loud enough to damage a person’s hearing. This is particularly important on construction sites and in manufacturing facilities where workers may be exposed to long-term sound exposure. Many sports stadiums and arenas also use meters to display the level of crowd noise.
A sound level meter measures sound in units known as decibels (dB). The threshold for human hearing is 0bD. A normal conversation typically measures between 60dB and 70dB, and damage to human hearing begins at a sustained level of 90dB. Damage to hearing can occur before the sound becomes loud enough to be physically painful, so it is important to use meters to verify sound levels. Safe sound levels for a working environment in the United States are set by the Occupational Safety and Health Administration (OSHA).
In addition to workplace safety, a sound level meter is often used to test sound levels when setting up speakers for public address systems. This allows everyone in the crowd hear the speaker clearly. Audio enthusiasts may also use an SLM to test the speakers in a home or car stereo system.
Most SLMs are battery-powered devices about the size of a cell phone. These devices can have digital or analog displays and feature large microphones. As of 2011, a basic meter generally costs under $50 US Dollars (USD). More expensive models usually have greater sensitivity and can log multiple measurements for larger site surveys. These higher-end models can cost several hundred USD.
If safety is not the primary issue, most consumers will probably only need a basic sound level measure. If the user needs to measure sound levels under 50dB or has to make precise measurements, he should invest in a more expensive model. More expensive devices may also allow a user to make measurements using different sound frequencies.
Noise dosimeters are another type of sound measuring device often used in conjunction with SLMs. Similar to chemical or radiological dosimeters, a noise dosimeter tracks how much sound exposure a person receives while wearing the device. This can more accurately predict whether a person has been exposed to damaging levels of sound. Another simple device, a noise indicator, will monitor sound and alert a user when he should put on hearing protection. Use of a sound level meter or other sound measuring device can greatly increase long-term worker safety and well being in a loud workplace.