Simple Explanation

A filter that sharply cuts off all sound above or below a certain frequency.

Concise Technical Definition

A filter with an extremely steep frequency rolloff (typically >50 dB per octave), designed to allow frequencies within a certain range to pass while nearly eliminating all others, creating a response that resembles a vertical "brick wall" on a graph.

Layman-Friendly Analogy

Like a strict bouncer at a club—only certain people (frequencies) get in, and everyone else is stopped instantly at the door.

Industry Usage Summary

Used in audio processing, telecommunications, and digital systems where minimal frequency leakage is crucial—such as anti-aliasing filters in analog-to-digital converters or in mastering audio to restrict frequency bands.

Engineering Shortcut

Brickwall = filter with near-infinite slope (ideal cutoff).

Full Technical Explanation

A brickwall filter refers to a low-pass, high-pass, or band-pass filter characterized by extremely sharp rolloff rates, typically greater than 50 dB/octave. This means the filter quickly transitions from full signal passage to near-total attenuation, making its response curve resemble a vertical wall. While ideal in theory, brickwall filters can introduce time-domain distortions (e.g., ringing) and are difficult to implement perfectly in analog systems.