`For 14 headphones and 40 human subjects, transfer functions were meas
ured from the voltage at the headphone terminals to the sound pressure
at the entrance to the blocked ear canal. For all headphones the freq
uency responses were characterized by smooth fluctuations at low frequ
encies and rather individual high-Q resonances at high frequencies. Da
ta were also obtained on the headphones' acoustical loading of the ear
canal. The main objective of the investigation was an evaluation of t
he headphones as a means for the reproduction of binaural signals, but
the transfer functions were also compared with design goals adequate
for the reproduction of normal stereo recordings.