Determining the levels of an audio signal.
In electronics, headroom means the margin between the nominal level of a signal and the maximum level that a given system can handle properly (ie before the device's saturation results clipping of the signal), and is often expressed in decibels. The term headroom is frequently used in the audio field to describe the capacity of an amplifier circuit to handle signals of greater than nominal amplitude.
For example, an amplifier designed to accept its signal input at a nominal level of -10 dBV that saturated to +20 dBV would have a headroom of 30 dB.
The headroom concept is complementary to the signal-to-noise ratio: in fact, compared to the nominal level of the signal, the first describes the upper margin before the system saturation, while the second describes the lower margin before the background noise of the system. By using these two concepts, it is possible to describe the range within which a system can properly handle a signal before it is degraded by saturation or background noise.
The distortion phenomenon that occurs when the signal exceeds the headroom is exploited in the music field - exclusively in the handling of analog audio signal - especially by using valve amplifiers to obtain particular timbres. This technique is called overdrive and allows you to get what is commonly called "sound crunch". The alteration of the analog audio signal above (or near) of the Headroom threshold occurs gradually; while its exasperation produces deliberately distorted sonority, a minimum saturation is perceived as a hottest, less dry sound, such as when audio recordings on magnetic tapes are made analogously, slightly exceeding the tape headroom levels same; this does not produce high fidelity of the recorded signal than that recorded, but this alteration is perceived by many as a pleasing sound effect.
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