Why Audio Feedback Happens and How to Stop It: Fixing Echo and Loops in Video Calls

Feedback comes from a sound loop

Feedback happens in a cycle: a mic in the same space picks up the sound from a speaker, and that sound comes out of the speaker again. Each time round, the sound gets a little louder, until one frequency is suddenly amplified into a squeal or a howl.

• The mic can pick up the speaker’s sound (no earphones are being used).
• The mic and speaker are close together, or the mic is very sensitive.
• The volume is high. The higher it goes, the more the sound grows with each loop.
• Two or more devices in the same room have joined the same meeting.

Put the other way round, breaking any one of these four stops the feedback. Cutting the loop in one place is almost always faster than finding the cause first and then fixing it. If you’re in a meeting, start by plugging in earphones or turning down the speaker volume.

Narrow down the cause from the symptom

These problems tend to get lumped together as “the audio is weird”, but the cause and the fix differ by symptom. Decide which one you have first, and the fix follows immediately.

How to stop it right now during a meeting

1. 1

   Mute the device that’s making it

   Even if you don’t know who’s causing it, if everyone mutes in turn, the device responsible is the one that stops the noise. Prioritize keeping the meeting going and leave pinpointing the cause for later.

2. 2

   Plug in earphones or a headset

   Once no sound comes out of the speaker, the mic has nothing to pick up and the loop is broken. This is the most reliable and fastest fix for feedback.

3. 3

   Turn down the speaker volume

   Without earphones, lower the volume. Once the loop’s gain drops below 1, the squeal stops. Make it as quiet as you can while still being able to hear.

4. 4

   Move the mic and speaker apart

   If you’re using external speakers, move them out from in front of the mic and put some distance between them. A laptop’s built-in mic and speakers are only a few centimeters apart, so if you can’t separate them, switch to earphones.

5. 5

   Check the meeting app’s echo cancellation

   Most meeting apps have an acoustic echo cancellation setting. Check that it isn’t off, and that you haven’t enabled features such as “original sound” or a “high-fidelity mode”. These can weaken echo cancellation.

When there are several devices in the same room

Several people joining from one meeting room on their own laptops is the situation most likely to cause feedback. B’s mic picks up A’s speaker and A’s mic picks up B’s speaker, creating a double loop.

• In one room, decide on just one device to play sound. Turn off both the speaker and mic on every other device.
• If everyone needs to speak, everyone uses earphones. If even one person uses a speaker, a loop forms.
• If the meeting room has a built-in speakerphone, routing everything through that one device is the most stable setup.
• When you move from your desk to a meeting room, check that your audio settings haven’t reset when you rejoined.

If one person is still joining through a speaker, there’ll be echo every time they talk. Simply saying “if you’re in the same room, please use earphones” at the start cuts trouble during the meeting a lot.

What to check before the meeting

It’s easier to join in a state where feedback can’t happen than to fix it once it starts. With a browser-based mic test, you can check your input device and audio processing in a minute.

1. 1

   Reselect the mic you’ll use

   If you plug in earphones but the input device is still the laptop’s built-in mic, only the output switches to earphones and the built-in mic keeps picking up the room. Choose the mic you’ll actually use from the input device list.

2. 2

   Check that echo cancellation and noise suppression are on

   The mic test lets you toggle Echo cancellation, Noise suppression and Auto gain control before starting the test, and shows which settings were actually applied. Unless you have a particular reason, leave all three on.

3. 3

   Record and listen back

   Record your voice and listen back through earphones. Problems such as echo or loud background noise can’t be judged from the level meter alone.

4. 4

   Always monitor through earphones

   The monitor feature, which lets you hear your own voice in real time, causes feedback on the spot if used with speakers. Always connect earphones when you use monitoring.

FAQ

What’s the difference between feedback, echo and reverberation?

Feedback is when a loop of the mic picking up the speaker amplifies one frequency into a sustained squeal. Echo is when your own voice comes back slightly late, usually because the other side’s speaker sound is leaking into their mic. Reverberation is reflection off the room’s walls that makes things sound like a bathroom. The causes and the person who fixes them differ, so work out which one it is first.

I’m using earphones but there’s still feedback. Why?

Even if you’re on earphones, if someone in the same room has joined the same meeting through a speaker, a loop forms on their device. Also, if you plug in earphones but the input device is still the laptop’s built-in mic, it keeps picking up nearby speakers. Use a mic test to check which input device is actually being used.

Will turning up the meeting app’s noise suppression stop feedback?

Often not. Noise suppression reduces steady background noise such as air conditioning or pages turning, but it doesn’t break the loop itself. What works on feedback is echo cancellation and physically breaking the loop (earphones, lower volume, more distance). Break the loop first, then review the settings.

How do I prevent feedback when recording or streaming?

The basic rule is to send your monitor sound only to earphones and never out of speakers. If you must use speakers, move the mic out from in front of them, bring a directional mic close to your mouth and turn the speaker volume down. Testing for a few dozen seconds at your real volume before going live is the safe approach.