Decibel meter12/17/2023 The reference pressure is set by the International agreement to be 20 micropascals for airborne sound. Root-mean-square sound pressure being obtained with a standard frequency weighting and standard time weighting. This is 20 times the base 10 logarithm of the ratio of given root-mean-square sound pressure to the reference sound pressure. The output of the RMS circuit is linear in voltage and is passed through a logarithmic circuit to give a readout linear in decibels (dB). I-time-weighting is no longer in the body of the standard because it has little real correlation with the impulsive character of noise events. Their names were changed in the 1980s to be the same in any language. Three of these time-weightings have been internationally standardized, 'S' (1 s) originally called Slow, 'F' (125 ms) originally called Fast, and 'I' (35 ms) originally called Impulse. The standard sound level meter can be called an exponentially averaging sound level meter as the AC signal from the microphone is converted to DC by a root-mean-square (RMS) circuit and thus it must have a time constant of integration today referred to as the time-weighting. They are the "conventional" sound level meter, the integrating-averaging sound level meter, and the integrating sound level meter. The IEC 61672-1 specifies "three kinds of sound measuring instruments". 4.1 Building acoustics, sound insulation and reverberation time.3.10 Pattern approval and periodic testing.2.3 L AT or L eq: Equivalent continuous sound level.In 1980, Britain's Cirrus Research introduced the world's first handheld sound level meter to provide integrated L eq and sound exposure level (SEL) measurements. This was to comply with the 1969 Walsh-Healey Act, which demanded that the noise in USA workplaces should be controlled. which became the first company to display sound exposure times on the scale of a sound level meter, as well as the sound level. In 1969, a group of University researchers from California founded Pulsar Instruments Inc. The world's first hand-held and transistorized sound level meter, was released in 1960 and developed by the Danish company Brüel & Kjær. These metrics can also be calculated in a number of different ways. Specific loudness is a compressive nonlinearity and varies at certain levels and at certain frequencies. 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 performances is the IEC 61672-1:2013. 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. Using this information, the instrument is able to accurately convert the electrical signal back to sound pressure, and display the resulting sound pressure level ( decibels dB SPL). The instrument needs to know the sensitivity of the particular microphone being used. 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.Ī microphone is distinguishable by the voltage value produced when a known, constant root mean square sound pressure is applied. the sound pressure (unit pascal, Pa), is converted into an electrical signal (unit volt, V). That is why the instrument is sometimes referred to as a sound pressure level meter (SPL). The diaphragm of the microphone responds to changes in air pressure caused by sound waves. The best type of microphone for sound level meters is the condenser microphone, which combines precision with stability and reliability. It is commonly a hand-held instrument with a microphone. An integrating-averaging Cirrus Research's Optimus sound level meter which complies with IEC 61672-1:2002Ī sound level meter (also called sound pressure level meter ( SPL)) is used for acoustic measurements.
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