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Such large measurement ranges are conveniently expressed in logarithmic scale: the base-10 logarithm of 10 12 is 12, which is expressed as a sound intensity level of 120 dB re 1 pW/m 2. The reference values of I and p in air have been chosen such that this corresponds approximately to a sound pressure level of 120 dB re 20 μPa.
Using estimates from the International Organization for Standardization (ISO 1999:2013), [47] the authors calculated that 99% of children who are exposed from birth until the age of 18 years to 8-h average sound levels (LEX) of 82 dBA would have hearing thresholds of about 4.2 dB greater, indicating a shift in hearing ability. By including a 2 ...
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.
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 ]
However, decibels are a logarithimic scale, so that successive 10 dB increments represent greater increases in loudness. For humans, normal hearing is between −10 dB(HL) and 15 dB(HL), [ 2 ] [ 3 ] although 0 dB from 250 Hz to 8 kHz is deemed to be 'average' normal hearing.
In the UK, the Permitted Maximum Level is 8 dB above Alignment Level, corresponding to '6' on the British PPM scale. ITU-T standards for international sound programme circuits specify a Permitted Maximum Level of 9 dB above Alignment Level. Accordingly, +9 dB is represented by a mark on the EBU PPM scale.
The unit dB FS or dBFS is defined in AES Standard AES17-1998, [13] IEC 61606, [14] and ITU-T Recs. P.381 [15] and P.382, [16] such that the RMS value of a full-scale sine wave is designated 0 dB FS. This means a full-scale square wave would have an RMS value of +3 dB FS.
Vinyl microgroove phonograph records typically yield 55-65 dB, though the first play of the higher-fidelity outer rings can achieve a dynamic range of 70 dB. [25] German magnetic tape in 1941 was reported to have had a dynamic range of 60 dB, [26] though modern-day restoration experts of such tapes note 45-50 dB as the observed dynamic range. [27]