A sound level meter measures acoustic pressure and converts it into decibel readings. This handheld device uses a condenser microphone to detect changes in air pressure caused by sound waves.
Core Components and Operation
The heart of a sound level meter is its condenser microphone, which transforms sound pressure (measured in pascals) into electrical signals (measured in volts). The device applies a logarithmic conversion to display sound pressure levels in decibels (dB), with 0 dB SPL equal to 20 micropascals.
Measurement Classifications
Sound level meters come in two primary classes:
- Class 1: High-precision instruments with wider frequency range
- Class 2: Standard instruments with broader tolerances
The American National Standards Institute (ANSI) further divides meters into three types:
- Type 0: Laboratory use
- Type 1: Field precision measurements
- Type 2: General-purpose measurements
Frequency Weighting Systems
A-Weighting and Alternatives
The meter uses different weighting systems to mirror human hearing sensitivity:
- A-weighting: Matches human hearing at quiet levels
- C-weighting: Better represents loud sounds (near 100 dB SPL)
- Z-weighting: Measures all frequencies equally
Time Response Options
The meter offers three standardized time responses:
- Fast (F): 125ms response time
- Slow (S): 1-second response time
- Impulse (I): 35ms response time
Historical Development
The first handheld transistorized sound level meter emerged in 1960 from Brüel & Kjær. In 1969, Pulsar Instruments Inc. pioneered displaying sound exposure times. Cirrus Research introduced the first handheld meter with integrated Leq measurements in 1980.
Applications
Sound level meters serve crucial roles in:
- Industrial noise monitoring
- Environmental assessment
- Mining operations
- Aircraft noise measurement
- Building acoustics
Modern Innovations
Current sound level meters often include:
- Remote communication capabilities
- GPS integration
- Weather monitoring
- Solar power options
- Real-time alerts via email and text
The technology continues to evolve with smartphone-based applications, though these typically don’t match the accuracy of professional instruments.
Citations:
https://en.wikipedia.org/wiki/Sound_level_meter
A sound level meter (also called sound pressure level meter (SPL)) is used for acoustic measurements. It is commonly a hand-held instrument with a microphone. The best type of microphone for sound level meters is the condenser microphone, which combines precision with stability and reliability. The diaphragm of the microphone responds to changes in air pressure caused by sound waves. That is why the instrument is sometimes referred to as a sound pressure level meter (SPL). This movement of the diaphragm, i.e. the sound pressure (unit pascal, Pa), is converted into an electrical signal (unit volt, V). While describing sound in terms of sound pressure, a logarithmic conversion is usually applied and the sound pressure level is stated instead, in decibels (dB), with 0 dB SPL equal to 20 micropascals.
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A microphone is distinguishable by the voltage value produced when a known, constant root mean square sound pressure is applied. This is known as microphone sensitivity. The instrument needs to know the sensitivity of the particular microphone being used. Using this information, the instrument is able to accurately convert the electrical signal back to sound pressure, and display the resulting sound pressure level (unit decibel, dB).
Sound level meters are commonly used in noise pollution studies for the quantification of different kinds of noise, especially for industrial, environmental, mining and aircraft noise. The current international standard that specifies sound level meter functionality and performances is the IEC 61672-1:2013. However, the reading from a sound level meter does not correlate well to human-perceived loudness, which is better measured by a loudness meter. Specific loudness is a compressive nonlinearity and varies at certain levels and at certain frequencies. These metrics can also be calculated in a number of different ways.[example needed]
The world's first hand-held and transistorized sound level meter, was released in 1960 and developed by the Danish company Brüel & Kjær. In 1969, a group of University researchers from California founded Pulsar Instruments Inc. which became the first company to display sound exposure times on the scale of a sound level meter, as well as the sound level. This was to comply with the 1969 Walsh-Healey Act, which demanded that the noise in US workplaces should be controlled. In 1980, Britain's Cirrus Research introduced the world's first handheld sound level meter to provide integrated Leq and sound exposure level (SEL) measurements.