The touch area is on the earbuds (both on the left and right).
For your reference, the detailed control methods are as follows:
1. For a call, tap the touch area twice to answer or hang up the call. Tap three times to reject the call;
2. For music playback, tap the touch area twice to pause or play the music. Tap three times to switch to the next song;
3. Press and hold the touch area for two seconds to switch modes among [Transparency], [Noise cancellation] and [Off].