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The decibel (symbol: dB) is a relative unit of measurement equal to one tenth of a bel (B). It expresses the ratio of two values of a power or root-power quantity on a logarithmic scale. Two signals whose levels differ by one decibel have a power ratio of 10 1/10 (approximately 1.26) or root-power ratio of 10 1/20 (approximately 1.12). [1] [2]
Example: A 16-bit system has 2 16 different possibilities, from 0 – 65,535. The smallest signal without dithering is 1, so the number of different levels is one less, 2 16 − 1. So for a 16-bit digital system, the Dynamic Range is 20·log(2 16 − 1) ≈ 96 dB. Sample accuracy/synchronisation Not as much a specification as an ability.
When sensorineural hearing loss (damage to the cochlea or in the brain) is present, the perception of loudness is altered. Sounds at low levels (often perceived by those without hearing loss as relatively quiet) are no longer audible to the hearing impaired, but sounds at high levels often are perceived as having the same loudness as they would for an unimpaired listener.
A 0.1% open area will reduce the transmission loss from 40 dB to 30 dB, which is typical of walls where caulking has not been applied effectively [26] Partitions that are inadequately sealed and contain back-to-back electrical boxes, untreated recessed lighting and unsealed pipes offer flanking paths for sound and significant leakage. [27]
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]
For example, for a 20 kHz analog audio sampled at 4× oversampling with second-order noise shaping, the dynamic range is increased by 30 dB. Therefore, a 16-bit signal sampled at 176 kHz would have a bit depth equal to a 21-bit signal sampled at 44.1 kHz without noise shaping.
Motion of the medium itself. If the medium is moving, this movement may increase or decrease the absolute speed of the sound wave depending on the direction of the movement. For example, sound moving through wind will have its speed of propagation increased by the speed of the wind if the sound and wind are moving in the same direction.
Though the noise level of 16-bit audio systems (such as CD players) is commonly quoted (on the basis of calculations that take no account of subjective effect) as −96 dB relative to FS (full scale), the best 468-weighted results are in the region of −68 dB relative to Alignment Level (commonly defined as 18 dB below FS) i.e. −86 dB ...