Spectral cues utilized in the localization of sound in the median sagittal plane

A series of experiments was carried out to further elucidate the role of spectral cues in locating sounds in the median sagittal plane (MSP). Broadband noise bursts, generated at ±30°, ±15°, and O° re aural axis, were recorded via microphones placed in the external ear canals of 8 Ss. When these recorded sounds were played back dichotically through headphones, they were perceived as originating from the loudspeakers, not the headphones. In fact, Ss could identify that loudspeaker which originally generated the sound nearly as accurately as they could when listening under free-field conditions. Analysis of the spectra of these recorded sounds revealed a notch in the frequency response curves which migrated toward the lower frequencies as the sound source was moved from above to below the aural axis. This feature of the spectrum may well be important for accuracy in locating sounds emanating from the frontal segment of the MSP. Four Ss were given additional tests to find out whether they could locate sounds recorded from one another’s ear canals. All Ss immediately externalized the recorded sounds. However, differences between performances among the various tapes of recorded sounds were statistically significant, suggesting that spectral cues provided by some Ss were more efficacious than others in furnishing information on the elevation of sound sources.