Both the loudness of a sound and the apparent magnitude of a self-produced vocal response (autophonic response) can be described as power functions of sound pressure, although with different exponents. Two scales, one of loudness, the other of autophonic level, can therefore be specified as a function of the same sound pressures. Under these circumstances theory predicts that loudness should be proportional to the square root of apparent autophonic level. Two separate but similar classroom experiments were performed, in each of which one person made autophonic responses of six different magnitudes whose loudnesses were judged by the members of the class. The obtained exponents between the two scales so erected was 0·52 in one demonstration and 0·53 in the other, thus confirming the prediction. The experiments used no apparatus since the only specification of the stimulus required was that the sound pressure produced by one subject should be the same as that judged by another.