Audio Repair and Restoration

How to remove hum from a recording in REAPER

By StudioRescue Editorial

Published July 19, 2026 · Updated July 19, 2026

Hum is the low, steady drone that sits under a recording and never goes away. It usually comes from the electrical mains, and once it is in the file it can feel like the whole take is ruined. The good news is that mains hum is one of the most predictable problems in audio: it lives at fixed, known frequencies, which makes it one of the more removable kinds of noise.

This guide covers how to identify hum, when to fix it at the source instead, and two ways to reduce it in REAPER with stock plugins: a surgical notch with ReaEQ, and noise subtraction with ReaFIR. It also covers what these tools will not do, so you know when to stop.

What hum actually is

Mains hum is electrical noise from the power supply leaking into your signal. Its pitch is not random. It sits at the frequency of the local power grid: 60 Hz in North America, and 50 Hz in most of Europe, Asia, Africa, and Australia. On top of that fundamental, the sound picks up harmonics, which are multiples of the base frequency. For 60 Hz power those land at 120, 180, 240 Hz and so on; for 50 Hz power they land at 100, 150, 200 Hz.

That harmonic content is why people describe two different sounds:

• Hum is dominated by the low fundamental. It sounds like a soft, round drone.
• Buzz has strong higher harmonics. It sounds harsher and brighter, more like a fluorescent tube or a bad ground.

Knowing your region tells you which frequency to target first. If you are in the United States or Canada, start at 60 Hz. If you are in the UK or most of Europe, start at 50 Hz. One helpful fact: those fundamentals sit below the normal range of a speaking or singing voice, so you can often remove the lowest hum without touching the voice at all.

Fix the source first

Plugins are a repair, not a cure. Before you process anything, it is worth knowing whether you can just re-record clean, because that always sounds better than removing hum afterward.

• Ground loops. A faint hum that appears only when two pieces of gear are connected is often a ground loop. Try plugging your interface and computer into the same power strip, or test on battery power if you have a laptop.
• Cheap USB power. Some USB interfaces and mics pick up hum from a noisy port or hub. Try a different port, or a powered hub.
• Dimmers and fluorescent lights. Light dimmers, some LED drivers, and fluorescent fixtures inject buzz into nearby audio gear. Switching them off during a take can remove the problem entirely.
• Cable routing. Keep audio cables away from power cables and wall-wart transformers, and cross them at right angles rather than running them in parallel.

Identify the hum before you cut

Confirm what you are dealing with so you target the right frequency.

Method 1: notch it out with ReaEQ

This is the right first move for a clean, steady hum where the fundamental dominates. ReaEQ has a dedicated Notch band type, which passes everything except a narrow range centered on the frequency you choose. Add ReaEQ to the track.

1. Notch the fundamental

Set the first band to Notch and place it at your mains frequency, 60 Hz or 50 Hz. In ReaEQ, bandwidth is measured in octaves, so start very narrow, roughly 0.1 to 0.3 octaves, so you carve out the hum without gutting the low end around it. Narrower is safer; widen only if the hum still pokes through.

2. Add notches for the audible harmonics

If the buzz has clear harmonics, add a band for each one you actually heard in the sweep, at 120 and 180 Hz for 60 Hz power, or 100 and 150 Hz for 50 Hz. Keep these narrow too. You usually do not need every harmonic, only the loud ones. Chasing all of them tends to do more harm than good.

Method 2: subtract it with ReaFIR

When the noise is more than a pure tone, a buzz with many harmonics, or hum mixed with hiss, ReaFIR’s Subtract mode often does better than a stack of notches. It listens to a sample of the noise, builds a profile of it, and then subtracts that profile from the whole track. REAPER’s own documentation calls this mode “excellent for Noise Reduction,” and points to faint hum or hiss as the ideal use.

If you need a little more reduction, hold Ctrl and drag the profile curve upward, but do it sparingly. Raising the profile removes more noise and also introduces more artifacts, that watery or swirly sound that gives away heavy noise reduction. If you hear it, drag back down. There is also a Reduce artifacts option in ReaFIR that trades some effectiveness for cleaner, more linear filtering if the swirl bothers you.

Which method should you use?

These are not mutually exclusive. A common order is to notch the obvious fundamental with ReaEQ, then let ReaFIR clean up whatever buzz and hiss remain.

What this will not fix

Hum removal has real limits, and pushing past them makes things worse, not better.

• It will not fix noise that changes over time. A profile-based subtraction assumes the noise is steady. Intermittent crackle, movement, or a hum that wanders in pitch will not subtract cleanly.
• It cannot separate hum from music that shares the same frequency. If a bass note sits right on 60 Hz, a notch there will dent the bass too. You are trading a little musical low end for less hum.
• It will not undo distortion or clipping that was recorded along with the hum. Damaged peaks are a different problem, and EQ or subtraction cannot rebuild them.
• Aggressive settings add artifacts. Past a certain point you are adding a new, weirder noise to remove an old, predictable one.

If it still hums

Quick troubleshooting order when the noise will not go away:

1. You targeted the wrong frequency. Re-check your region. A notch at 60 Hz does little for 50 Hz hum, and the other way around.
2. The buzz is mostly harmonics. If notching the fundamental barely helped, the energy is up in the multiples. Switch to ReaFIR Subtract or add notches at the harmonics you can hear.
3. Your notches are too wide. If the fix made the track sound thin or hollow, narrow the bandwidth. The hum is one tone, so the cut can be very narrow.
4. It is not steady. If the noise moves or comes and goes, subtraction cannot track it. That is a source problem, and re-recording after fixing grounding or cabling is the real fix.