Sony WI-1000XM2 Help Manual page 98

Use a smartphone or mobile phone at least 50 cm (19.69 in.) away from the headset. Noise may result if the smartphone or
mobile phone is too close to the headset.
Your voice will be heard from the headset through the headset's microphone (Sidetone function). In this case, ambient sounds or
the sounds of the headset operation may be heard through the headset, but this is not a malfunction.
Related Topic
How to make a wireless connection to Bluetooth devices
Receiving a call
Functions for a phone call
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