Air conditioning drowning out a recording: how to fix it

You play back a meeting recording and there it is:a steady roar of air conditioning under everything. Or a cheap microphone has left a constant hiss over the whole thing. The voices are there, but listening is oddly exhausting.

That kind of continuous noise can now be removed in a browser. Here is what it sounds like before and after.

1. Listen to it first

Someone reading out a meeting note, with the sound of a conference-room air conditioner mixed in.The same ten seconds, before and after.

Before

After

Levels are matched. The voice stays where it was; the roar behind it drops away. Use headphones or a quiet room.

2. How to remove it

1. Open Remove noise.
2. Press “Get ready”. This loads the part that tells speech from noise, once (about 11MB).
3. Drop the recording in.
4. Press “Remove the noise”, compare against the original, then save.

Nothing is uploaded — it all runs in your browser. Meetings and one-to-one recordings are usually the last thing you want to hand to a stranger, so it is built that way. Once the setup has finished you can disconnect from the internet and it still works end to end.

3. What it handles, and what it does not

Handled well

• Air conditioning, extractor fans, computer fans — anything steady
• The hiss of a cheap microphone or a phone recording
• Mains hum

Difficult

• Background chatter. Café noise and the conversation at the next desk cannot be removed: other people talking is also speech, so there is nothing to tell them apart by. It has to be avoided at recording time
• One-off sounds. A cough or a chair is not continuous noise, so it stays
• Music. The model keeps speech, so singing and instruments get damaged

4. Keeping it out in the first place

Not recording it beats removing it. Three things make most of the difference:

• Get the microphone closer. Halve the distance and the voice arrives four times louder, while the room noise stays exactly as loud. This is the big one
• Don't sit directly under the air-conditioning vent. One seat along is enough
• Don't rest the recorder on a laptop. It picks up the fan and the vibration. A book or a folded cloth underneath already helps

5. Do this before fixing the volume

If the recording is also too quiet, remove the noise first, then raise the volume.The other way round amplifies the noise as well, which leaves you worse off.

1. Remove noise
2. Fix the volume

There is more on levels inA recording is too quiet to hear: how to fix it.

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