the beat goes on

Kraig Grady stated:

>I am not convinced that two pitches 100 and 101 sounded together
are percieved as 100.5 with a beat rate of 1. First how can this be
meaused.

This is a standard result in psycho-acoustics. For instance,
there's an extended description and a couple of figures describing it
in Roederer's book (Physics and Psychophysics of Music).

On page 31 there is a footnote:

How do we verify that, indeed, the pitch sensation of the resulting
tone does correspond to a tone of frequency f1+delta f/2? This is
accomplished with pitch matching experiments: the subject is
presented alternatively with a reference tone of controllable pitch
and is requested to "zero in" the frequency of the latter until he
senses "equal pitch" with respect to the original tone.