#4 A shift in their voice
It is a natural stress response for people to tense up the muscles in and around their vocal cords when they are anxious. The voice may come off as high-pitched as a result. The voice of the liar may also have squeaks and cracks in it.
Normally, you can detect a person’s speech’s natural rhythm and flow. However, when a voice raises in pitch or when the volume or pace picks up, it’s time to pay attention.
As we instinctively conceal and muffle our voices when we’re discussing something we shouldn’t be sharing with others, a liar’s voice may grow higher or louder due to nervousness, or alternatively, they may speak more quietly (almost like they’re telling you a secret).