Filter any audio file in your browser. Choose low-pass, high-pass, band-pass or notch, set the cutoff and Q, and watch the frequency response and your audio's spectrum update as you go. Preview with an instant before/after switch, then save as WAV or MP3.
Last updated:
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Filter responseSpectrum beforeSpectrum after
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How to use the Audio Low-Pass and High-Pass Filter
Open an audio file by dropping it on the box or clicking to choose. A demo clip with hiss is loaded so you can try the filters right away.
Pick a filter type (low-pass, high-pass, band-pass or notch) or click a preset.
Set the frequency and Q with the sliders, the number boxes, or by dragging across the graph.
Press Play preview and use the Filter on / Original switch to compare.
Choose WAV or MP3 and press Download filtered audio.
Which filter for which job?
Goal
Filter
Starting settings
Remove rumble, traffic and mic-stand thumps
High-pass
60-100 Hz, 24 dB/oct, Q 0.71
Clean up a boomy voice
High-pass
100-150 Hz, 12 dB/oct
Soften hiss on an old recording
Low-pass
6-8 kHz, 24 dB/oct
Music from the next room / underwater
Low-pass
300-600 Hz, 36 dB/oct
Isolate bass or kick drum
Low-pass
100-200 Hz, 48 dB/oct
Telephone or walkie-talkie voice
Band-pass
1-1.5 kHz, Q 1-1.5, 2 stages
Old AM radio
Band-pass
1.5-2 kHz, Q 0.7
Remove a whistle or feedback tone
Notch
The tone's frequency, Q 10-20
Remove electrical hum
Notch
50 or 60 Hz; use the Hum Remover for the harmonics too
How the filters work
Each filter is built from second-order "biquad" sections, the standard building block of digital audio equalizers, run by your browser's Web Audio engine. One section gives a 12 dB per octave slope; this tool cascades up to four sections for 24, 36 or 48 dB per octave. For low- and high-pass, the sections use Butterworth Q values (for example 0.54 and 1.31 for a 24 dB slope) so the passband stays flat. Raising Q above 0.71 increases the resonance of the last section, giving the classic synth-style peak at the cutoff.
For band-pass and notch filters, Q sets the width: bandwidth = center frequency ÷ Q. A notch at 1,000 Hz with Q 10 removes a band roughly 100 Hz wide. In octaves, the bandwidth is N = (2 ÷ ln 2) × asinh(1 ÷ 2Q), so Q 1.41 is about one octave and Q 4.3 about a third of an octave.
Tips
Use the gentlest slope that does the job; steep filters can make audio sound boxy or "phasey".
Watch the orange after-spectrum: if the part you want to keep drops, move the cutoff further away.
Band-pass and notch filters lower the overall level. Raise the output gain a little and leave Prevent clipping on.
Switch between Filter on and Original often; your ears adapt quickly to a filtered sound.
Frequently asked questions
What is the difference between a low-pass and a high-pass filter?
A low-pass filter lets frequencies below the cutoff pass and reduces the ones above it, so it removes hiss and brightness. A high-pass filter does the opposite: it keeps frequencies above the cutoff and removes lows such as rumble, wind and handling noise.
What cutoff frequency should I use?
For speech, a high-pass between 80 and 120 Hz removes rumble without thinning the voice. A low-pass around 6 to 8 kHz softens hiss on old recordings, while 300 to 500 Hz gives a strongly muffled, next-room sound. For a telephone effect, keep roughly 300 Hz to 3.4 kHz with a band-pass around 1 to 1.5 kHz.
What does Q mean on a filter?
Q describes how sharp the filter is around its frequency. For low- and high-pass filters, Q 0.71 gives a flat Butterworth response that is 3 dB down at the cutoff; higher Q adds a resonant bump. For band-pass and notch filters, Q equals the center frequency divided by the bandwidth, so a higher Q means a narrower band.
What does 12, 24 or 48 dB per octave mean?
It is how quickly the filter cuts beyond the cutoff. At 12 dB per octave, a frequency one octave past the cutoff is about 12 dB quieter; at 48 dB per octave it is about 48 dB quieter, which is a much steeper wall. Steeper slopes are more surgical but can sound less natural.
Will filtering reduce the quality of my audio?
Filtering only changes the frequencies you choose; the rest of the sound is untouched. Saving as WAV keeps the result lossless. Saving as MP3 adds normal MP3 compression, so use 192 or 320 kbps for music.
Is my audio uploaded?
No. Decoding, filtering and encoding all happen in your browser with the Web Audio API. The MP3 encoder is a small script downloaded once; WAV export works fully offline.
How is the spectrum graph calculated?
The tool averages up to 120 FFT frames of 8,192 samples across your file, smooths the result to about a twelfth of an octave and scales the loudest part to 0 dB. The after spectrum adds the filter's response to it, so you can see exactly which parts of your audio will be reduced.
Are all the tools on FreeToolCabin tested for quality and accuracy?
Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.