| Popis: |
Selected pure‐tone pulses (1 to 13.7 kHz) were directed toward a methyl methacrylate replica of the left external ear from a large albino rabbit. Sound‐pressure measurements were taken 4 msec after pulse‐envelope arrival through a 14‐in. calibrated condenser microphone situated within the auditory canal. The signal was amplified, displayed on a CRO, and photographed for analysis. The 12‐cm pinna served to diffract directionally sounds of wavelengths smaller than its dimensions. Sensitivity in the horizontal plane 90° to 150° ipsilateral to the pinna opening produced amplifications of 20 dB re 0.0002 dyn/cm2 at the canal base for frequencies 2.2, 5, 8, and 10 kHz. Vertical and horizontal angles displayed marked frequency dependence. Sound‐pressure measurements at the base and opening of the auditory canal suggest that cavity resonance interacts with the pinna‐diffraction effects and is dependent upon the azimuth of the incident sound. [Supported by a National Science Foundation grant to R. A. Suthers.] |
