LG LM-V600EA Mode D'emploi page 45

There are two microphones built into this product. Be careful not to cover
the microphones. While you are talking on the phone, do not cover the
microphone with your hand or fingers.
Do not use a phone case that is not a genuine product or cover the
microphone with accessories, tape, etc.
Hold the product correctly as shown in the image when you are using it.
Good example Bad example
Microphone
Microphone
Microphone Do not cover the microphone.
Basic Functions 44