SOLIPSIUMAlpha
SOLIPSIUM Super resolution audio engine
Hum and buzz
Drop a recording and Solipsium measures its hum in your browser: the mains frequency and how far the hum stands above nearby frequencies. Then hear the first 20 seconds repaired.
Drop a humming recording here
Solipsium checks it in your browser for hum, noise and clipping, without uploading it. It can then repair the first 20 seconds for you to hear, with no account.
WAV, MP3, M4A, video and more, up to five minutes.
After signing up, drop the same file into the editor to repair all of it.
Scans and short repairs are free.
How it works
Mains power runs at 50 Hz or 60 Hz, depending on the country, and equipment on that power can leak the tone into a recording. Hum is a line at that frequency and its multiples; buzz is the same line with strong harmonics. The check in your browser names steady hum with its frequency, how many decibels it stands above nearby frequencies, and when it was heard.
The repair averages up to 30 one-second stretches of the recording. Hum counts when its lines at 50 or 60 Hz and their multiples stand 10 dB above the frequencies around them, the fundamental or the third harmonic among them, over a noise floor that holds steady.
Each notch is 3 Hz wide and shifts nothing in time. Where steady hum is found, the first four harmonics are always notched, and higher ones up to the 24th where they stand 8 dB out. The result reads: “Mains hum was found, so it is notched out before any cleanup.”
Wherever the notches removed almost nothing, read a tenth of a second at a time, the untouched recording is put back. Hum that a low voice hides from the average is looked for in the quiet moments and notched the same way.
Hum in parts of a recording is found by its steady phase, measured 2 seconds at a time, in spans of at least 3 seconds. Only those spans are notched, with a quarter-second fade at each edge, and the try's reason says: “Mains hum was found in parts of the recording, so it is notched out there; the voice is put back wherever the notches removed nothing.”
Questions
A 60 Hz supply also puts lines at 120, 180 and 240 Hz and up, and a 50 Hz supply at 100, 150 and 200 Hz. Buzz carries them past 1 kHz. A single notch at the mains frequency leaves every harmonic in place, so Solipsium notches the first four each time and any higher one that stands out.
When the buzz sits on a steady 50 or 60 Hz line, it is hum with strong harmonics, and the harmonics that stand out are notched with it. A buzz with no steady mains line under it is not labelled hum, and neither is a tone at another frequency.
The measure over the whole recording can miss it. A second measure then finds the spans where it plays and notches only there, and the result names that repair in its own sentence.
A little: the notches also cut the voice's own sound at the hum's frequencies, in bands 3 Hz wide. Switch between Original and Repaired as they play, on one clock, and compare them on the same words.
Solipsium's free try is built for speech. The notches run under music too, and music can lose a little bass at 50 or 60 Hz.
Not for the check, which runs in your browser. Pressing Repair the first 20 seconds sends those 20 seconds; when your browser could not open the file, or it runs over five minutes, the file itself goes to Solipsium's server, so the try is offered for it only up to 25 MB. Solipsium keeps only the first 20 seconds and deletes them within an hour. If you are signed in, a file you drop or choose is uploaded to your account and opens in the editor instead. The privacy notice has the rest.
Free audio tools
Turn down rumble, lower hiss, or clean up a tape you captured.
Check a recording for noise, hum and clipping, and hear its first 20 seconds repaired.
Turn down low rumble under a voice, below 300 Hz, after the other repairs.
Measure steady hiss with no sample of the noise, and hear 20 seconds repaired.
Check a captured tape for hum, hiss, clipping and gaps, and hear 20 seconds repaired.
Find and break the loop behind the hum before the next take.
Every free tool on one page.
With a free account, Suggested repair and the editor's Remove hum work on all of it.
Free account, no card.