To find out if there’s an issue with the microphone on your device—and not your cellular connection or the app that you're using—test each microphone. Microphone location can vary by device. You can use your product's technical specifications to find the microphones.
There is more than one microphone on your iPhone.
To test the primary microphone on the bottom of your iPhone, open Voice Memos and tap the record icon. Then speak into the microphone and tap the play icon to play back the recording. You should be able to hear your voice clearly.
If your voice sounds faint when you’re using the speakerphone on a phone call, make sure that your iPhone receiver isn’t blocked or covered.
If audio from video recordings sounds faint, or Siri can’t hear you, make sure that the microphone near the iSight camera—on the top, back corner of your iPhone—and the receiver isn’t blocked or covered.
To test the microphone on your iPad, record a video using the Camera app, then play back the recording. You can also use FaceTime to make a video or audio call to test the sound quality.
To test the microphone on your iPod touch, open Voice Memos. Tap the record icon, speak into the microphone, then tap the play icon to play back the recording. You should be able to hear your voice clearly.