SLM (Sound-Level Meter) is a device (usually hand-held) utilized to determine sound levels in a systematic format. It relates to sound in about the same way as the human ears and provides objective, repeatable measures of sound pressure thresholds. Let’s take a closer look at it.

What is a sound meter usually used for?

Sound-level meters are used to monitor and control noise from a number of locations including manufacturing facilities, rail and road traffic, and building construction. With the addition of traditional urban environments, such as sporting activities, outdoor concerts, recreational parks and business and residential neighbours, you have several different sources of noise, each with distinct traits that pose unique problems for the experts who evaluate them.

How do they work?

The sound-level meter contains of a mic, a preamplifier, a signal processor and a monitor. The microphone transforms the signal into an analogous electrical signal. The most appropriate type of mic for sound-level meters is a condenser microphone, which blends accuracy with availability and security.

The electronic impulse generated by the mic is at a very low level, making the preamplifier stronger until it is analysed by the main processor. Signal processing requires the application of frequency and time weightings to signals as defined by global standards such as IEC 61672-1, which comply with sound level meter.

sound level meter
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Calibration

Calibration is the configuration of your SLM to calculate and show the correct measurements. The responsiveness of the transducer, as well as the reaction of the digital circuits, can differ slightly over time or may be influenced by environmental parameters such as humidity and temperature.

Although you might never encounter a significant drift or shift in SLM sensitivity, it is still advisable to check your SLM’s calibration periodically, typically before and after each series of data. The easiest way to do this is to position a handyaudible calibrator direct over the mic. This will have a specifically definite sound compression to which the sound-level meter can be attuned.

In addition to testing the calibration before and after readings, many laws and guidelines regulating sound level measurements also mandate your SLM to be adjusted once every 12 or 24 months in a lab.

International Standards

International rules are relevant because they’re used explicitly or because they provide guidance or comparison to state standards. There are 2 major international organizations that are dealing with standardization.

The International Organization for Standardization (ISO) is mainly concerned with a framework to guarantee that protocols are specified to allow comparison of results. The International Electrotechnical Commission (IEC) works with instruments in order to see that they are compliant and can be shared without a substantial loss of accuracy or data.

This is a basic breakdown of what a sound-level meter is. How the device works is purely technical and one should have at least a basic knowledge of physics and in order to grasp it. If you are interested look it up.

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