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The decibel originates from methods used to quantify signal loss in telegraph and telephone circuits. Until the mid-1920s, the unit for loss was miles of standard cable (MSC). 1 MSC corresponded to the loss of power over one mile (approximately 1.6 km) of standard telephone cable at a frequency of 5000 radians per second (795.8 Hz), and matched closely the smallest attenuation detectable to a ...
The scaling is such that the EPNdB rating represents the integrated noisiness over a ten-second period; EPNdB of 100 dB means that the event has the same integrated noisiness as a 100 PNdB sound lasting ten seconds. Direct comparison with A-weighted sound pressure level, which is used for many other environmental sound measurements, is not ...
Multiple noise processes determine the noise floor of a system. Noise can be picked up from microphone self-noise, preamp noise, wiring and interconnection noise, media noise, etc. Early 78 rpm phonograph discs had a dynamic range of up to 40 dB, [24] soon reduced to 30 dB and worse due to wear from repeated play. Vinyl microgroove phonograph ...
Signal-to-noise ratio (SNR or S/N) is a measure used in science and engineering that compares the level of a desired signal to the level of background noise. SNR is defined as the ratio of signal power to noise power, often expressed in decibels. A ratio higher than 1:1 (greater than 0 dB) indicates more signal than noise.
The day-night average sound level (Ldn or DNL) is the average noise level over a 24-hour period. The noise level measurements between the hours of 22:00 and 07:00 are artificially increased by 10 dB before averaging. This noise is weighted to take into account the decrease in community background noise of 10 dB during this period.
Sound exposure level (SEL) is a logarithmic measure of the sound exposure of a sound relative to a reference value. Sound exposure level, denoted L E and measured in dB , is defined by [ 1 ]
The STC or sound transmission class is a single number method of rating how well wall partitions reduce sound transmission. [3] The STC provides a standardized way to compare products such as doors and windows made by competing manufacturers. A higher number indicates more effective sound insulation than a lower number.
The threshold of hearing is plotted relative to a standardised curve that represents 'normal' hearing, in dB(HL) (hearing level). They are not the same as equal-loudness contours , which are a set of curves representing equal loudness at different levels, as well as at the threshold of hearing , in absolute terms measured in dB(SPL) (sound ...