I bought JBL headphones and found out they have these holes on both sides. What are they for? They're empty and kinda deep, the headphones aren't wireless so I guess it's not
HEADSET HEADPHONE JBL T600 BT NC BLACK (PN:TL0612) - MDP IT & Electronic Store
JBL Tune 700BT - wireless, over-ear bluetooth headphones with streaming and voice assistant, up to 27 hours of music playback, in black: Amazon.co.uk: Electronics & Photo