The cupped hand as an aid to hearing.

The acoustic effects of cupping the hand behind the ear were measured by means of a miniature microphone placed at the entrance to the ear canal. Pure tone signals from 0.2 to 10 kHz, at 1/3-octave intervals, were used. Amplification was produced when subjects were facing the sound source, mainly in the mid-frequency range, where there was a peak of 8 dB around 1.6 and 2 kHz. When the subjects had their backs towards the sound source, the effect produced was attenuation, the maximum being 9.5 dB at 2.5 kHz.