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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]
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]
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.
Decibels relative to full scale (dBFS or dB FS) is a unit of measurement for amplitude levels in digital systems, such as pulse-code modulation (PCM), which have a defined maximum peak level. The unit is similar to the units dBov and decibels relative to overload (dBO). [1] The level of 0 dBFS is assigned to the maximum possible digital level. [2]
A gray-scale photography with different signal-to-noise ratios (SNRs). The SNR values are given for the rectangular region on the forehead. The plots at the bottom show the signal intensity in the indicated row of the image (red: original signal, blue: with noise).
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]
While 1 atm (194 dB peak or 191 dB SPL) [11] [12] is the largest pressure variation an undistorted sound wave can have in Earth's atmosphere (i. e., if the thermodynamic properties of the air are disregarded; in reality, the sound waves become progressively non-linear starting over 150 dB), larger sound waves can be present in other atmospheres ...
Loudness Units referenced to full scale Loudness measurement unit on an absolute scale, K-weighted, [3] relative to a digital scale (the upper limit of which is 0 dBFS). Equivalent with LKFS, used in ITU-R BS.1770. LU Loudness Unit Relative loudness measurement. 1 LU corresponds to the relative measurement of 1 dB on a digital scale. LU can ...