Home Theater & Entertainment Audio High Pass Filter Filters are a basic part of the audio experience By Gary Altunian Writer Gary Altunian was a freelance contributor to Lifewire and industry veteran in consumer electronics. He passion was home audio and theater systems. our editorial process Gary Altunian Updated March 11, 2020 Darryn van der Walt / Getty Images Audio Speakers Stereos & Receivers Tweet Share Email A high-pass filter allows high frequencies to pass but cuts, or attenuates, frequencies below a threshold point. How Audio Speakers Use High-Pass Filters A high-pass filter is used in an audio system to allow high frequencies to get through while filtering or cutting low frequencies. A high-pass filter is used with small speakers to remove bass, for example. In many cases, these filters are built into the speaker, but in some more elaborate do-it-yourself speaker setups, a high-pass filter unit can be wired to the system. How High-Pass Filters Work With Microphones Some brands of microphones include a selectable filter. These devices, usually intended for higher-end recording, automatically block sounds below a specific hertz rating. These settings are useful when recording in places like office buildings or warehouses where the HVAC system maintains a low rumble. These filters capture the signal while eliminating the nose. It's better to capture good audio than to fix bad audio in post-processing. A microphone with an onboard filter yields better audio quality than a normal microphone that's been fixed algorithmically after the recording session concludes. How to Use High-Pass Filters in Audio Editing In tools like Audacity, a high-pass filter that is applied to a waveform simulates a hardware filter. It attenuates sound below a given threshold. Specify a frequency in hertz and the roll-off in decibels per octave. Audacity then attenuates the relative volume (the dB) of the signal with increasing intensity the further below the threshold frequency the signal lies. Many audio-editing environments include similar functionality. How High-Pass Filters Work A high-pass filter (like its cousin, the low-pass filter) uses some technique to eliminate or reduce input below a specific threshold. There's no specific way that it works. Wikipedia Some filters offer a hard cap, effectively silencing noise below the threshold, while others taper off the signal below a certain point.