Headphone CheckStereo channel test
Left and Right Audio Test
Check that sound meant for your left ear plays on the left and sound meant for the right plays on the right, with nothing missing in between. Works for headphones, earbuds, headsets and speakers.
Press Left, then Right. The lit side shows where each sound should come from.
Polarity (wiring) check
Keep the volume around 50%.
How to read the left/right test
There are only four possible results, and each one points to a different cause:
| What you hear | What it means |
|---|---|
| Left on the left, right on the right | Channels are correct. If the centre sound also sits in the middle, your stereo is fine. |
| Left and right are swapped | The headphones are on backwards, or software is swapping the channels (see below). |
| Both sounds in both ears | Mono audio is on, or a Bluetooth headset is in hands-free (call) mode. |
| One side silent or much quieter | A balance setting, a blocked mesh, a flat earbud, a damaged cable or a failed driver. Follow the one-earbud fix guide. |
Left and right are swapped: how to fix it
- Check the markings. Over-ear headphones have L and R inside the earcups or on the headband; earbuds have them on the stem or the inner side. On some neckband and gaming models the cable always goes on the left.
- Check the software. Audio drivers and "enhancement" apps (Realtek Audio Console, Dolby Access, Nahimic, Sonic Studio, Equalizer APO) can swap channels. Turn their effects off and test again.
- Check the cable. A third-party extension cable or adapter can be wired with left and right reversed. Test without it.
- Check the source. A few videos and games simply have swapped channels. If the test on this page is correct but one video is not, the problem is the video.
The sound is pulled to one side
Play Both / centre. If the sound leans left or right instead of sitting in the middle of your head, check the balance slider before anything else:
- Windows 11: Settings → System → Sound → your output device → Left channel / Right channel.
- Mac: System Settings → Sound → Output → Balance.
- iPhone: Settings → Accessibility → Audio & Visual → Balance.
- Android: Settings → Accessibility, then Audio balance (on Pixel it sits under Audio; on Samsung under Hearing enhancements → Left/right sound balance).
If the balance is centred and one side is still quieter, the cause is physical: earwax on the mesh, an earbud tip that does not seal, or an ageing driver. Cleaning the mesh with a dry soft brush fixes it more often than you would expect.
What the stereo sweep and polarity checks add
The stereo sweep moves a tone smoothly from ear to ear. With healthy headphones it travels like a slow wave, never jumping. A crackle or a gap at one point on the way usually means a worn cable or a dirty plug; wiggle the cable near the jack while the sweep plays and listen for the dropout.
The polarity check plays the same low tone in both ears, first in phase and then with one side inverted. In phase sounds solid and centred; out of phase sounds wide, hollow and thin. That difference is the point: if your everyday music always sounds like the out-of-phase version, one side of the headphones (or one speaker) is wired backwards. On speakers, swap the red and black wires on one of them.
Testing speakers instead of headphones
The same buttons work for a pair of speakers or a soundbar. Sit centred between the speakers. The left beep should come only from the left speaker, the right beep only from the right, and the centre sound should appear as a phantom image right between them. For 5.1 or 7.1 systems use the surround sound test.
Frequently asked questions
How do I know which earbud is left and which is right?
Look for a small L or R on the stem, the inner side or the case slot. If there is no marking, play Left on this page: the earbud that makes a sound is the left one.
Why does sound come out of both earbuds when I play the left channel?
Mono audio is switched on in your phone or computer's accessibility settings, or the headset is in hands-free mode because an app is using its microphone. Turn mono off and close any call or voice app, then test again.
Is a left right sound test the same as a stereo test?
Yes, mostly. A left right test plays each channel separately; a stereo test also checks the image between them, which is what the centre and stereo sweep buttons do.
Can I test left and right on a phone speaker?
Many phones have stereo speakers, one at the top and one at the bottom. Hold the phone sideways and play Left and Right; on single-speaker phones both sounds come from the same place, which is normal.