Simple Explanation

The point where a filter starts to noticeably reduce (or boost) the signal level.

Concise Technical Definition

The frequency at which the output of a filter drops by 3 decibels (−3 dB), marking the beginning of the filter’s transition band.

Layman-Friendly Analogy

Like the bend in a road where it starts to turn—past that point, things begin to change direction noticeably.

Industry Usage Summary

Used in filter design, loudspeaker crossovers, equalization, and signal processing to indicate the threshold at which attenuation begins. Often called the −3 dB point because it corresponds to a ~30% power loss in signal.

Engineering Shortcut

Corner Frequency = −3 dB point = start of significant roll-off.

Full Technical Explanation

The corner frequency (or cutoff frequency) is the point in the frequency response of a filter where the output signal level is reduced by 3 decibels compared to the passband level. In analog and digital signal processing, this defines the boundary between the passband (where signals pass relatively unaffected) and the stopband (where signals are attenuated). It's critical for designing effective filters, crossovers, and EQ curves.