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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 ...
I 0 is the reference sound intensity; 1 Np = 1 is the neper; 1 B = 1 / 2 ln(10) is the bel; 1 dB = 1 / 20 ln(10) is the decibel. The commonly used reference sound intensity in air is [5] = /. being approximately the lowest sound intensity hearable by an undamaged human ear under room conditions.
Source of sound Distance Sound pressure level [a] (dB SPL) Shock wave (distorted sound waves > 1 atm; waveform valleys are clipped at zero pressure) [11] [12] >1.01×10 5 >191 Simple open-ended thermoacoustic device [14] [clarification needed] 1.26×10 4: 176 1883 eruption of Krakatoa [15] [16] 165 km 172 .30-06 rifle being fired 1 m to shooter ...
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 ...
Standards using different reference levels, give rise to differences in audiograms. The ASA-1951 standard, for example, used a level of 16.5 dB SPL (sound pressure level) at 1 kHz, whereas the later ANSI-1969/ISO-1963 standard uses 6.5 dB SPL, with a 10 dB correction applied for older people.
1 dB = 1 / 20 ln 10 is the decibel. The commonly used reference sound exposure in air is [2] = . The proper notations for sound exposure level using this reference are L W/(400 μPa 2 ⋅s) or L W (re 400 μPa 2 ⋅s), but the notations dB SEL, dB(SEL), dBSEL, or dB SEL are very common, even if they are not accepted by the SI.
The sound energy density level gives the ratio of a sound incidence as a sound energy value in comparison to the reference level of 1 pPa (= 10 −12 pascals). [2] It is a logarithmic measure of the ratio of two sound energy densities. The unit of the sound energy density level is the decibel (dB), a non-SI unit accepted for use with the SI ...
The first research on the topic of how the ear hears different frequencies at different levels was conducted by Fletcher and Munson in 1933. Until recently, it was common to see the term Fletcher–Munson used to refer to equal-loudness contours generally, even though a re-determination was carried out by Robinson and Dadson in 1956, which became the basis for an ISO 226 standard.