A high pass filter lets through the high frequencies and blocks the low ones

A high pass filter is a tool that removes low frequencies from sound or other signals while keeping the high frequencies intact. Think of it like a screen that stops heavy bass notes from getting through but lets treble and crisp sounds pass. The exact point where it starts blocking depends on how the filter is set up — you can adjust where that cutoff happens.

You encounter high pass filters in real situations more often than you might think. Audio engineers use them to clean up recordings by removing rumble from traffic or air conditioning. Musicians use them on individual instruments during mixing. Your phone's microphone might have one built in to reduce wind noise when you're recording video outside. The filter doesn't delete the low frequencies — it just turns them down so they don't dominate what you're hearing or recording.

Key Takeaways

  • A high pass filter removes low frequencies and keeps high frequencies, which is the opposite of what a low pass filter does.
  • The cutoff frequency is the point where the filter starts blocking sound, and you can usually adjust it depending on what you're trying to accomplish.
  • High pass filters are used in audio recording to remove rumble and unwanted low-frequency noise that muddies the sound.
  • You can explore a high pass filter to a single instrument, a whole mix, or just your microphone input depending on what software or equipment you're using.

How the cutoff frequency works

Every high pass filter has a cutoff frequency — a specific frequency measured in hertz where the filter starts doing its job. Frequencies below that point get reduced, and frequencies above it pass through mostly unchanged. If you set the cutoff at 100 Hz, everything below 100 Hz gets turned down, and everything above stays loud.

The cutoff isn't a hard wall where sound suddenly stops. Instead, the filter gradually reduces volume as frequencies get lower. This gradual slope is called the roll-off, and it's usually measured in decibels per octave. A steeper roll-off means the filter blocks low frequencies more aggressively. A gentler roll-off means low frequencies fade out more gradually. Most audio software lets you choose how steep the roll-off is, which gives you control over how aggressive the filtering sounds.

Why audio engineers use high pass filters

The main reason to use a high pass filter is to remove unwanted rumble and low-frequency noise that makes recordings sound muddy or unprofessional. A microphone picking up traffic outside, an air conditioner humming in the background, or the rumble of someone's hand brushing a microphone stand — all of these create low frequencies that don't carry useful information and just clutter up the recording.

When mixing music, engineers often put a high pass filter on vocals, guitars, and drums to clean up each track individually. A vocal recording might have rumble from the room that you can't hear clearly but that takes up space in the mix. Filtering it out makes the vocal sound clearer and gives the mix more room for the bass guitar and kick drum, which are supposed to handle the low end. The same principle applies to any instrument that doesn't need to produce very low frequencies.

High pass filters versus low pass filters

A low pass filter does the opposite job — it lets low frequencies through and blocks high frequencies. If a high pass filter removes rumble, a low pass filter removes harshness and hiss. They're often used together in mixing: a high pass filter cleans up the low end of a track, and a low pass filter softens the high end.

The choice between them depends on what you're trying to remove. If a recording has wind noise or traffic rumble, you need a high pass filter. If it has harsh sibilance (the "s" sound in vocals) or digital artifacts, you might reach for a low pass filter instead. Many audio interfaces and mixing software include both, so you can use whichever one solves your problem.

Where you'll find high pass filters in practice

Most digital audio workstations — software like Audacity, GarageBand, or Ableton Live — include a high pass filter as a standard tool. You can explore it to a single audio track, a group of tracks, or your entire mix. Some come as straightforward sliders where you just choose a cutoff frequency, while others let you adjust the roll-off and see a visual graph of what the filter is doing.

Many microphones and audio interfaces have a physical high pass filter button, usually labeled HPF or a symbol that looks like a high-pass filter curve. Turning it on automatically removes low frequencies at a preset cutoff (often around 80 Hz or 100 Hz) without you having to open any software. This is especially useful for live recording or streaming, where you want to clean up the signal in real time.

How to use a high pass filter without overdoing it

The most common mistake is setting the cutoff too high and removing frequencies that actually belong in the recording. If you're filtering a vocal and you set the cutoff at 500 Hz, you'll remove important warmth and body from the voice. A safer starting point is usually 80 Hz to 150 Hz for most instruments and vocals — low enough to catch rumble but high enough to preserve the sound you want.

The best approach is to listen while you adjust. Turn the filter on and off and listen to the difference. Slowly raise the cutoff frequency until the unwanted rumble disappears, then back it off slightly so you're not removing anything you need. If you're not sure whether the filter is helping, it probably isn't — leave it off. A high pass filter should be invisible when it's working correctly; you should only notice it when you turn it off and hear the rumble come back.

Frequently Asked Questions

Is a high pass filter the same as a noise gate?

No. A noise gate silences audio below a certain volume level, while a high pass filter reduces specific frequencies. A gate is all-or-nothing — sound either passes through or it doesn't. A filter gradually reduces volume at low frequencies. They solve different problems and are often used together.

Can I use a high pass filter on a bass guitar or kick drum?

You can, but you have to be careful. Bass instruments are supposed to produce low frequencies, so a high pass filter will damage their sound if the cutoff is too high. If you need to remove rumble from a bass track, use a very gentle filter with the cutoff set low — around 30 Hz to 50 Hz — so you're only catching the deepest rumble, not the actual bass notes.

What's the difference between a high pass filter and an equalizer?

An equalizer lets you boost or cut specific frequency ranges across the whole spectrum. A high pass filter only removes frequencies below a certain point. An EQ is more flexible, but a high pass filter is simpler and faster when you just want to remove low-frequency rumble without thinking about other adjustments.

Do I need to use a high pass filter on every track?

No. Only use a high pass filter if a track actually has unwanted low-frequency noise. If a recording sounds clean without it, leave it off. Overusing filters can make a mix sound thin and unnatural. Use them only where they solve a real problem.