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Washington [vague] (Chapter 70.107) sets maximum levels in dB(A) but allows 5 dB(A) more if the sound is only 15 minutes in an hour, or 10 dB(A) for 5 minutes in an hour. Numerous cities have fixed levels, permitting excess levels for short times (e.g., Dallas, TX, Chapter 30) while others use Leq (Lincoln, NE, Chapter 8.24).
The maximum dynamic range of a 16-bit system is about 96 dB, [10] while for 24 bit it is about 144 dB. Dither can be used in audio mastering to randomize the quantization error, and some dither systems use Noise shaping to spectral shape of the quantization noise floor. The use of shaped dither can increase the effective dynamic range of 16-bit ...
[3] [10] Although specific regulations vary across the world, most workplace best practices consider 85 decibels (dB A-weighted) averaged over eight hours per day as the highest safe exposure level for a 40-year lifetime. Using an exchange rate, typically 3 dB, allowable listening time is halved as the sound level increases by the selected rate.
Such a difference can exceed 100 dB which represents a factor of 100,000 in amplitude and a factor 10,000,000,000 in power. [4] [5] The dynamic range of human hearing is roughly 140 dB, [6] [7] varying with frequency, [8] from the threshold of hearing (around −9 dB SPL [8] [9] [10] at 3 kHz) to the threshold of pain (from 120 to 140 dB SPL ...
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]
In sound measurement, we measure the loudness of the sound in decibels (dB). Decibels are logarithmic with 0 dB as the reference. [1] There are also a range of frequencies that sounds can have. Frequency is the number of times a sine wave repeats itself in a second. [2] Normal auditory systems can usually hear between 20 and 20,000 Hz. [2]
For these, IEC 60268-10 requires a minimum of 100 segments and a resolution better than 0.5 dB at the higher levels. Many operators prefer the moving-coil meter type of display, in which a needle moves in an arc, because they feel the angular movement is easier for the human eye to monitor than the linear movement of a bar graph.
The graph indicates how this works. In this example, the input signal suddenly increases from 50 dB to 80 dB, stays there for 6 seconds, then drops back suddenly to the initial level. A slow measurement (yellow line) will take approximately 5 seconds (attack time) to reach 80 dB and around 6 seconds (decay time) to drop back down to 50 dB.