microphone MacBook Air volume low when using apps

When no additional programs are open, the input volume of my internal MacBook Air microphone is fine. Under Settings → Sound → Input, the input level looks good when I speak. However, when I use the Phone app, Google Meet, or any other app that uses the microphone, the other person can barely hear me. The input level is then zero or very low. As soon as I close the app, the input level returns to normal. What is wrong here?