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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. The proper notations for sound intensity level using this reference are L I /(1 pW/m 2 ) or L I (re 1 pW/m 2 ) , but the notations dB SIL , dB(SIL) , dBSIL, or dB SIL are very ...
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.
While one might expect speeding up to reduce comprehension, Herb Friedman says that "Experiments have shown that the brain works most efficiently if the information rate through the ears—via speech—is the 'average' reading rate, which is about 200–300 wpm (words per minute), yet the average rate of speech is in the neighborhood of 100 ...
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 ...
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 relationship between sound and noise levels is generally described in terms of a signal-to-noise ratio. With a background noise level between 35 and 100 dB, the threshold for 100% intelligibility is usually a signal-to-noise ratio of 12 dB. [3] 12 dB means that the signal should be roughly 4 times louder than the background noise. The ...
Auditory sensitivity changes when the duration of a sound becomes less than 1 second. The threshold intensity decreases by about 10 dB when the duration of a tone burst is increased from 20 to 200 ms. For example, suppose that the quietest sound a subject can hear is 16 dB SPL if the sound is presented at a duration of 200 ms.
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.