Audio Channel Fixer
Fix a recording that plays in only one ear: copy the good channel to both, mix or swap.
How It Works
Your browser decodes the file and measures the RMS level of the left and right channels across the whole recording. If one side is silent, the tool picks the matching fix for you. You can change it before clicking Fix channels. The new audio is written as a 16-bit WAV, and as an MP3 on request, without leaving your device.
Want to stop it happening next time? Read why a microphone records only in the left channel.
Why Audio Ends Up in One Ear
Most microphones are mono: they produce one signal. Many audio interfaces and recording apps record in stereo, with input 1 on the left and input 2 on the right. Plug one mic into input 1 and record in stereo, and you get your voice on the left and silence on the right. On speakers you may not notice. On headphones it sounds like the audio is only in one ear.
| What you hear | Best fix |
|---|---|
| Only the left ear | Copy left to both |
| Only the right ear | Copy right to both |
| Different sounds on each side, want one | Mix both into mono |
| Left and right are reversed | Swap left and right |
Mixing a recording where one side is silent gives a result about 6 dB quieter, because the silent side is averaged in. Copying keeps the full level. If the result is still quiet, use the volume booster.
Limits
The tool works on audio files only, not video. The whole file is decoded in memory, so very long recordings can be slow on phones. If your browser cannot detect the file's sample rate, the audio is resampled to 44.1 kHz.
Frequently Asked Questions
Why does my recording only play in one ear?
Usually because a mono microphone was recorded on one side of a stereo input. The voice lands in the left channel and the right channel stays silent, so headphones play it in one ear. It is common with USB audio interfaces and with mixers or adapters that put a single mic on input 1.
Should I copy the channel or mix to mono?
If one side is silent, copy the good channel to both. Mixing averages the two sides, so a silent side halves the level (about 6 dB quieter). Mixing is the right choice when both sides have useful sound, such as two microphones.
How does the tool know which side is silent?
It measures the loudness (RMS level) of each channel across the whole file and shows it in decibels. A channel below -60 dB is treated as silent, and one more than 20 dB quieter than the other is flagged as much quieter.
Will this lower the quality?
The WAV download is 16-bit PCM at the file's original sample rate where the browser can detect it, so nothing is lost beyond 16-bit precision. The MP3 download is encoded at 192 kbps, which is fine for speech and most music.
Which files can I fix?
MP3, WAV and M4A files your browser can decode, including most screen and voice recordings. Video files are not supported; extract the audio first. Only the first two channels of multichannel audio are used.
Is my recording uploaded?
No. Decoding, measuring and rewriting the channels all happen in your browser with the Web Audio API, and the MP3 is encoded on your device with lamejs.