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Loudness, a subjective measure, is often confused with physical measures of sound strength such as sound pressure, sound pressure level (in decibels), sound intensity or sound power. Weighting filters such as A-weighting and LKFS attempt to compensate measurements to correspond to loudness as perceived by the typical human.
The SI unit of intensity, which includes sound intensity, is the watt per square meter (W/m 2). One application is the noise measurement of sound intensity in the air at a listener's location as a sound energy quantity. [3] Sound intensity is not the same physical quantity as sound pressure. Human hearing is sensitive to sound pressure which is ...
Equal-loudness contours. The phon is a logarithmic unit of loudness level for tones and complex sounds. Loudness is measured in sones, a linear unit.Human sensitivity to sound is variable across different frequencies; therefore, although two different tones may present an identical sound pressure to a human ear, they may be psychoacoustically perceived as differing in loudness.
The sensitivity is measured at 1 watt to minimize nonlinear effects such as power compression and harmonic distortion, and averaged over the usable bandwidth. The bandwidth is often specified between the measured '+/-3 dB' cutoff frequencies where the relative loudness becomes attenuated from the peak loudness by at least 6 dB.
However, the reading from a sound level meter does not correlate well to human-perceived loudness, which is better measured by a loudness meter. Specific loudness is a compressive nonlinearity and varies at certain levels and at certain frequencies. These metrics can also be calculated in a number of different ways. [4] [example needed]
[28] [29] [30] This means that at short durations, a very short sound can sound softer than a longer sound even though they are presented at the same intensity level. Past around 200 ms this is no longer the case and the duration of the sound no longer affects the apparent loudness of the sound.
ISO equal-loudness contours with frequency in Hz. An equal-loudness contour is a measure of sound pressure level, over the frequency spectrum, for which a listener perceives a constant loudness when presented with pure steady tones. [1] The unit of measurement for loudness levels is the phon and is arrived at by reference to equal-loudness ...
Dynamic range is a measure of how small you can measure a signal relative to the maximum input signal the device can measure. Expressed in decibels, the dynamic range is 20 log (Vmax/Vmin). For example, a device with an input range of ±10 V and a dynamic range of 110 dB will be able to measure a signal as small as 10 μV.