How to Remove Hum and Hiss from a Recording
Scope, up front: this guide cleans a recording — a file that already exists. Noise happening live is a different problem entirely; everything below happens after the fact.
First diagnose: hum is a constant low drone at exactly 50 or 60 Hz (plus harmonics) — electrical in origin; hiss is fizzy broadband noise across the high end — electronic or environmental. Hum wants a notch filter at the mains frequency (in Audacity: Effect → EQ and Filters → Notch Filter); hiss wants profile-based noise reduction. Treating one with the other's cure is how recordings get ruined twice.
Tool paths verified Jul 29, 2026 in Audacity 3.7.8 (Notch Filter, Noise Reduction) and Adobe Audition (DeHummer) · mains hum is 60 Hz in the Americas, 50 Hz most elsewhere.
Placeholder players — the real clips drop in at QA (see deploy notes for the file slots).
Step 1 — Diagnose by ear (and by eye)
- Listen to a silent stretch on headphones: a steady musical drone is hum; frying-pan fizz is hiss.
- Check the pitch: hum sits rock-still; hiss has no pitch at all.
- Confirm visually if unsure — Audacity's spectrogram view shows hum as thin horizontal lines at 50/60 Hz and its multiples, hiss as an even wash up top.
Why this matters: the cures are opposites. A notch is surgical and touches almost nothing; broadband reduction is a blanket. Swapping them either does nothing or damages everything.
Step 2 — Kill hum with a notch
- Open Effect → EQ and Filters → Notch Filter in Audacity.
- Set the frequency to 60 Hz (Americas) or 50 Hz (most elsewhere), Q around 8–10.
- Apply, then listen — if a thinner whine remains, notch the harmonics too: 120/180 Hz (or 100/150).
- In Audition, the DeHummer effect does the fundamental and harmonics in one dialog.
When it fails: hum that wobbles in pitch isn't mains hum — it's a motor or appliance. Notch filters need a stationary target; wobble pushes you back to broadband reduction or the source itself.
Step 3 — Kill hiss with a profile
- Sample 2–5 seconds of hiss-only audio — the standard profile method.
- Apply Noise Reduction gently: 10–12 dB, then a second pass if needed.
- Mind the highs: hiss lives where consonants live, so over-reduction lisps the voice before anything else.
Hiss removal is the classic trade: every dB of reduction spends a little treble. Gentle passes keep the spend where you can't hear it.
Step 4 — Fix the cause for next time
- Hum: reseat cables, separate audio and power runs, try a different outlet — ground loops die at the wiring.
- Hiss: raise the source, not the gain; more signal at the mic beats amplified noise every time.
- Both: a ten-minute setup fix outperforms every filter on this page.
Cleanup is the tax on capture. This site exists because the tax is real — but the best pass through this guide is the one you don't need next month.
Over-suppression has a distinct sound per disease: over-notched hum leaves the low end hollow, robbing voices of chest and warmth (too many harmonics notched, or Q too wide); over-reduced hiss produces the lisping, airless top end and the musical-noise sparkle. In both cases the fix is retreat — fewer notches, narrower Q, fewer dB — never a bigger hammer.
Still noisy? Escalate in this order
- Drone survives every notch? It's wobbling — treat it as broadband noise or fix it at the source.
- Hiss survives two gentle passes? You're at the floor; a third pass costs more voice than it removes.
- Both at once on an old tape? That's the archival guide's territory — order of operations matters there.
Quick questions
Why is my recording humming at exactly 60 Hz?
That's mains electricity bleeding into your signal — a ground loop, an unshielded cable, or a power supply too close to the mic line. 60 Hz in the Americas, 50 Hz most elsewhere; the harmonics at multiples are part of the same fingerprint.
Can one tool remove both hum and hiss?
Automated cleaners handle both in one pass, which is their honest advantage. Manually, you'll use two tools — notch then profile — and doing hum first gives the hiss pass a cleaner floor to learn from.
Does a notch filter damage the voice?
A narrow notch at 50/60 Hz sits below most voice fundamentals and is close to inaudible. Damage starts when notches multiply up the harmonic ladder or the Q widens — that's when warmth disappears.