#Noise decibel how to#

Sound levels for nonlinear (decibel) and linear (intensity) scalesĪrtillery fire at close proximity (threshold of pain)Īverage street noise loud telephone bellĪlthough the decibel scale is nonlinear, it is directly measurable, and sound-level meters are available for that purpose. (Sometimes the threshold of pain is given as 120 decibels, or 1 watt per square metre.) When the defining level of 0 decibel (10 -12 watt per square metre) is taken to be at the threshold of hearing for a sound wave with a frequency of 1,000 hertz, then 130 decibels (10 watts per square metre) corresponds to the threshold of feeling, or the threshold of pain. The correlation between the absolute intensity of a sound wave and its decibel level is shown in Table 1, along with examples of sounds at each level. Thus, an increase in absolute intensity from 10 -12 to 10 -11 watt per square metre corresponds to an increase of 10 decibels, as does an increase from 10 -1 to 1 watt per square metre. Because the decibel scale mirrors the function of the ear more accurately than a linear scale, it has several advantages in practical use these are discussed in Hearing, below.Ī fundamental feature of this type of logarithmic scale is that each unit of increase in the decibel scale corresponds to an increase in absolute intensity by a constant multiplicative factor. The reference intensity I 0, corresponding to a level of 0 decibels, is approximately the intensity of a wave of 1,000 hertz frequency at the threshold of hearing-about 10 -12 watt per square metre. Here L represents decibels, which correspond to an arbitrary sound wave of intensity I, measured in watts per square metre. Such a scale is provided by the sound intensity level, or decibel level, of a sound wave, which is defined by the equation Because of the enormous nonlinearity of the ear in sensing pressure waves, a nonlinear scale is convenient in describing the intensity of sound waves. The ear mechanism is able to respond to both very small and very large pressure waves by virtue of being nonlinear that is, it responds much more efficiently to sounds of very small amplitude than to sounds of very large amplitude.

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#Noise decibel how to#

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