The fastest way to check this is to leave the call running. Go to the app’s audio menu, pick your Mac’s microphone and play whatever was sounding wrong a minute ago. Keep the Bluetooth headphones selected as the speakers. If the change works, you’ll still hear the people on the call. The Mac will just be picking up your voice through a different mic.
What the change tells you
Apple has a support page for this particular problem. The Mac can use Bluetooth for higher-quality playback, or it can use the connection for playback and the microphone on the headphones at the same time. When the mic is in use you may notice a drop in volume as well as quality. Apple mentions static and popping too. That explains why a headset can sound fine for an album and then sound very different the next minute, even though you haven’t touched the player.
A good check takes about as much music as you’d use to show someone where a fault is. Pick out a few seconds where you can hear it. With the call app closed, play those seconds once and note what you heard. Now open a test call or a preview that uses the microphone. Select the headset mic and play the same section. For the last pass, stay on the call, change to the Mac mic and go back to the same spot. With any luck you’ll know by the time you get to the end of it. The bit that was clear with the app closed, then dull, then clear again is the result to watch for.
It’s easy to hit the wrong selector in a hurry. In an app with two menus, the speaker setting should be the same through all three listens. If your app uses the system input, look in System Settings under Sound, then Input. Apple shows the path here. Some apps keep a separate choice and will keep using the headset mic until you change it there.
Is the Mac mic close enough?
Try saying a few words to the person on the call after you switch. A laptop on a stand at the back of the desk might be far enough away that your voice suffers. You can go back to the headset mic if that’s what makes the call easier to hear. If you already have a separate microphone, try putting it where it can pick up your voice comfortably, with the same headphones still in use.
If switching made no difference, quit other apps that could be using the headphone mic. Apple also suggests selecting the headphones again as the output. A fault you hear before you start any call needs a different check. Try the same passage on the Mac’s speakers or listen to the headphones on another device. Do those one at a time and you’ll have a better idea where to look.
This guide uses Apple’s support notes. For the player side, there’s our Apple Music lossless setup guide. Save the player changes until you’re done with the mic comparison. Otherwise you may get cleaner sound without knowing which setting did it.