Double Tap for 'Mute' on AirPods

So, the answer to the original question about muting is "No." There is currently no way to mute/unmute the mic on a phone call using gestures or tapping on the airpods.

Yes.

While wearing either AirPod, two quick, sharp taps on the outside of that AirPod will answer a phone call or hang up the phone. Each AirPod can also do one of these:

• Activate Siri*
• Play and pause your audio content
• Skip to the next track
• Go back to the previous track
• Turn off your audio content

Use your AirPods - Apple Support

So, your answer to the question is not to answer the question.

You are correct, there is no mute function for the mic by tapping the airpods.