Accession Number : ADA164098

Title :   The Bat's Ear as a Diffraction Grating.

Descriptive Note : Master's thesis,

Corporate Author : AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING

Personal Author(s) : Sowell,William A.

Report Date : DEC 1983

Pagination or Media Count : 83

Abstract : The series of parallel evenly-spaced ridges found in most bats' ears are investigated to determine if they are acting as a diffraction grating. A diffraction grating causes a periodic transverse variation of phase or amplitude in an incident wave. Such a device might be useful to the bat in determining a target's relative vertical position. An experiment using ridged and smooth model ears (of the bat phyllostomus hastatus) was designed. Since the angle of diffraction is related to the angle of signal incidence, it should have been possible to observe periodic variations in amplitude across the frequency sweep received by a model ear. In calculating the predicted dispersion using the Huygen's-Fresnel principle it was determined that diffraction could not occur. The data appears to have supported this, and produced two further results. Significant differences in the data between the two model ears suggest a definite relationship between the ridges and the echolocation process. Also the ears are sensitive to angle of incidence in steps as small as five degrees. Keywords: Bats; Diffraction Grating; Echolocation; and Thesis.

Descriptors :   *GRATINGS(SPECTRA), *HEARING, *EAR, *ECHO RANGING, *BATS, ANGLES, POSITION(LOCATION), MODELS, THESES, TARGETS, VARIATIONS, DIFFRACTION, VERTICAL ORIENTATION, PERIODIC VARIATIONS, TRANSVERSE, SWEEP FREQUENCY TECHNIQUES.

Subject Categories : Anatomy and Physiology

Distribution Statement : APPROVED FOR PUBLIC RELEASE