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Term: Dynamic range

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Term: Dynamic range

Term used to describe the ratio between the smallest and largest possible values of a changeable quantity, frequently encountered in imaging or recorded sound. Dynamic range is another way of stating the maximum signal-to-noise ratio. To use sound as the example, this is the ratio of the loudest (undistorted) signal to that of the quietest (discernible) signal in a system as expressed in decibels (dB).

In images and sound recordings, the range that can be captured by a camera or microphone is more restricted than what might be perceived by a human who is standing at the location of that camera or microphone. Although humans can not experience the extremes of a given scale at a single viewing or listening, a human can see objects in dim starlight or in bright sunlight: a dynamic range of about 90 dB. A human is capable of hearing anything from a quiet murmur in a soundproofed room to the sound of the loudest rock concer: a dynamic range of more than 100dB, i.e., a multi-million-times difference in sound energy.

Contributing to the difficulty in broad-dynamic-range capture or reproduction by most electronic equipment is the fact that their behavior is linear rather than logarithmic like human perception. Electronically reproduced audio and video often uses clever adjustment in order to accommodate original material with a wide dynamic range. (See also gamma and gamma correction.) In the realm of sound, professional-grade analog signal processing equipment can output maximum levels of +26 dBu, with the best noise floors being down around -94 dBu, which gives a maximum dynamic range of 120 dB. (The unit dBu is referenced to a weighting function of 0.7746 volts.)
See also:
Bit depth (image); Bit depth (audio); Decibel; Gamma; Gamma correction; High dynamic range imaging; Signal-to-noise ratio