Why Call Recordings Sound Robotic, and What Helps
A call squeezes your voice into a small stream, cleans it on the fly and patches over lost packets. The robot sound is those steps showing. A little of it can be eased afterwards, and most of it is avoided by recording on each end.
By the fix.fm team · Published · Updated
What the robot sound is
A video or phone call doesn't send your voice as it was. The app cleans out background sound, squeezes what's left into a small stream, and sends it in tiny packets over the internet. When a step works too hard or a packet goes missing, you hear it, and a recording of the call keeps it.
Most robotic call audio is one of four things. Listen for which one you have before trying to fix it:
| What you hear | What usually caused it | What can help afterwards |
|---|---|---|
| Watery, warbly or metallic, worst on soft words | The call app's noise suppression working too hard | Very little. Avoid more noise reduction |
| Choppy, buzzy, syllables stretched or missing | Lost packets that the app papered over | Nothing brings the missing sound back |
| Thin and boxy, like an old phone | A phone line or a Bluetooth headset microphone | A little more clarity from what's left |
| Words cut short when two people talk at once | Echo cancellation turning one voice down | Nothing, but headphones prevent it |
Why it can't be fully undone
Each of these removes part of the voice before the file is saved. A phone line using the long-standing G.711 standard samples at 8 kHz, so nothing above about 4 kHz survives. That's where much of the crispness of S, F and T sounds lives. Internet calls usually do better, but modern call codecs such as Opus drop to a narrower band when the connection is poor, and fill short gaps from lost packets with a guess at the missing sound. That guess is the buzzy, stretched syllable you hear.
A repair tool can only work on the sound that was recorded. fix.fm cleans and balances that sound, so it won't invent a new voice, and it can't put back what the call threw away. A tool that rebuilds the voice from scratch, like Adobe's Enhance Speech, can sometimes get further on a very damaged call, at the cost of sometimes sounding like someone else. Our Adobe Podcast comparison goes through that trade.
What still helps
Start with the audio quality check. It tells you in plain words what's wrong with the file, so you only fix what needs fixing.
- Too quiet. Call recordings are often low. The quiet audio fix brings it up to podcast level without clipping.
- Thin or dull. The muffled audio fix brings up what's left of the upper detail. On a phone line there's nothing above about 4 kHz to bring up, so expect a modest change.
- Only in one ear. Some call recorders put each person on their own side. The one ear fix puts the voice in both.
- Background noise left over. Use noise reduction gently, or not at all. The call has usually removed noise once already, and a second pass on that sound tends to make the warble worse. Our note on noise reduction artifacts shows what to listen for.
Compare before and after at a similar volume. If the fixed version only sounds louder, it isn't better yet.
Record it right next time
The best fix for call audio is not recording the call at all, but each end of it.
- Record on each end. Ask every person to record their own microphone on their own computer or phone while you talk, then line the files up afterwards. Each file has the full voice with none of the call's damage. Many podcast recording services do this for you.
- Use wired headphones. They stop your speakers from feeding back into your mic, so echo cancellation has nothing to cut. Avoid using a Bluetooth headset's microphone: while it's in use, most headsets switch to a low quality call mode for both directions.
- Turn the app's noise suppression down in a quiet room. Most call apps let you lower it in their audio settings. In Zoom, the Original sound for musicians option turns most of the processing off. Turn it back on if you're somewhere noisy.
- Steady the connection. Plug in to the router if you can, and pause big uploads and downloads while you record.
Before a long session, make a one minute test call and record it, then listen back on headphones. Our guide to recording a clear voice covers the microphone and the room.