William Morris Hartmann
Andrew Wittenberg
Michigan State Univ., Dept. of Phys., East Lansing, MI 48824
Successful imaging of real sound sources by headphones can be done by measuring free-field head-related transfer functions (HRTF) using small microphones in the ear canals and then inverse filtering by the headphone response. A simpler alternative to this standard procedure is described where a listener, with small microphones in the ear canals, wears open-air headphones throughout the experiment. A synthesized vowel is played, first from a loudspeaker and then from the headphones. The headphone signal is adjusted so that the amplitudes and phases of the harmonics measured with the small microphones are the same as those found when the loudspeaker is sounding. The technique is successful in that listeners cannot distinguish between real and virtual sources. It lacks the flexibility of the HRTF technique, but it allows an experimenter to study the most interesting psychoacoustical questions about sound localization and externalization using an experimental technique that is simpler and probably more reliable. [Work supported by the NIDCD and by the NSF Research Participation for Undergraduates Program.]