Headroom and Distortion
If an audio signal is too strong, it will overdrive the audio circuit, causing the shape of
the signal to distort. In analog equipment, distortion increases gradually the more the
audio signal overdrives the circuit. For some audio recordings, this kind of distortion
can add a unique “warmth” to the recording that is difficult to achieve with digital
equipment. However, for audio post-production, the goal is to keep the signal clean
and undistorted.
0 dB on an analog meter refers to the ideal recording level, but there is some allowance
for stronger signals before distortion occurs. This safety margin is known as headroom,
meaning that the signal can occasionally go higher than the ideal recording level without
distorting. Having headroom is critical when recording, especially when the audio level is
very dynamic and unpredictable. Even though you can adjust the recording level while
you record, you can’t always anticipate quick, loud sounds. The extra headroom above
0 dB on the meter is there in case the audio abruptly becomes loud.