Left and right
Open the Speaker Test and play the left channel, then the right. The sound should come only from that side. If it comes from the other side, the speakers or the headphone cable are swapped; if it comes from both, the system may be set to mono (on Windows, Settings → Accessibility → Audio; on a Mac, System Settings → Accessibility → Audio).
One side is silent
- Check the balance slider in the sound settings is in the middle.
- For wired headphones, push the plug all the way in and turn it; a half-inserted plug often loses one channel.
- Try another pair of headphones on the same port to see whether the fault is in the headphones or the computer.
Bass and treble
People hear from about 20 Hz to 20,000 Hz, and the top limit drops with age. Play a sweep or single tones with the Tone Generator, starting quietly. Small laptop speakers often produce little below 150 Hz; good headphones reach 20 Hz. A buzz or rattle at one frequency points to a loose part in the speaker or nearby.
Keep the volume low
Pure tones sound much louder than music at the same setting and can damage hearing or speakers. Start low and turn up slowly, especially with headphones.