Sony WI-C100 Help Manual page 82

When using the voice assist function, 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.
If the headset's microphone rubs against your clothing, etc., noise may interfere with your voice input. When inputting a voice
command, change the direction of the remote control component so that the microphone's audio capture hole does not touch
your clothing, etc.
Siri may not be activated depending on specifications of the smartphone or application version.
Be careful because the headset will turn off when you press and hold the (play/call) button.
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