This is really fascinating:
Scientists used to consider the frequency band of 500 hertz and below
in the human voice as meaningless noise, because when a voice is
filtered, removing all higher frequencies, ne hears nothing but a
low-pitched hum. All words are lost. But then it was found that this
low hum is an unconscious social instrument. It is different for each
person, but in the course of a conversation people tend to converge.
They settle on a single hum, and it is always the lower status person
who does the adjusting. This was first demonstrated in an analysis of
the Larry King Live television show. The host, Larry King,
would adjust his timbre to that of high-ranking guests, like Mike
Wallace or Elizabeth Taylor. Low-ranking guests, on the other hand,
would adjust their timbre to that of King. The clearest adjustment to
King’s voice, indicating lack of confidence, came from former Vice
President Dan Quayle.
The same spectral analysis has been
applied to televised debates between U.S. presidential candidates. In
all eight elections between 1960 and 2000 the popular vote matched the
voice analysis: the majority of people voted for the candidate who held
his own timbre rather than the one who adjusted.
From this site.