Acoustical Beam Patterns for Bats: Some Theoretical Considerations

Abstract

Acoustical beam patterns for emission from several different bats are calculated assuming a piston source in an infinite baffle, both as single and as double emitters. The calculated beam patterns agree well enough with experimental values available in the literature to justify the assumptions used. For those bats which possess no facial appendages to serve as a baffle, the simple acoustical model does not work, as anticipated. The calculated beam patterns are for fixed frequencies in the examples used; however, some aspects of frequency modulated beams are briefly discussed.

Phylogeny of Phyllostomid Bats (Mammalia: Chiroptera): Data From Diverse Morphological Systems, Sex Chromosomes, and Restriction Sites

“…Interference between the emission from each nostril is apparently used to direct sound in the horizontal dimension (Hartley and Suthers, 1987). These results are similar to those for other species of bats in which the role of the noseleaf was studied (e.g., Megaderma and Rhinolophus; Möhres and Neuwiler, 1966;Strother and Mogus, 1970;Sokolov and Makarov, 1971;Schnitzler and Grinnell, 1977). Although other features of the noseleaf and horseshoe have not been studied in relation to their affect on echolocation pulses, it seems likely that these characters influence some aspects of pulse emissions.…”

Tight coordination of aerial flight maneuvers and sonar call production in insectivorous bats

“…5B). Assuming a constant emitter size, 5.9 mm as reported by Jakobsen and Surlykke (2010) for Eptesicus serotinus, similar to E. fuscus, we estimated the beam width using a piston model (Strother and Mogus, 1970). As the bats approached the first net opening, they decreased end frequency of the FM sweep from 26.2 to 23.4 kHz, which, according to the model, would increase the half-amplitude angle of their sonar beam by 10 deg, from 51 to 61 deg.…”

Radiation pattern of echolocation pulse in Taiwanese leaf-nosed bat, Hipposideros terasensis

“…This suggests that the horizontal radiation pattern in H. terasensis, as well as in other bats with nostril emitters, follows basic principles of combining simple sources. In several bats that emit echolocation through the nostrils, their nostril separations are known to be nearly equal to one-half the wavelength of the CF 2 frequency [6]. H. terasensis also has a nostril separation with a half wavelength of the CF 2 frequency.…”

“…For CF 3 , there was a sharp drop in the amplitude at 50 degrees in contrast to CF 2 . When the pulse is emitted through two nostrils as in Rhinolophus ferrumequinum, the radiation pattern can be estimated by considering a combination of simple sources placed closely enough so that interference occurs [6]. The estimated pattern is given by PðÞ ¼ 20 log cos…”

“…For a few echolocating bats with nostril emitters, the directionality of the emitted echolocation pulse has been discussed by considering a combination of simple sources placed closely enough so that interference occurs [6]. The second aim of this report is to examine whether the directionality obtained from the echolocation pulse of H. terasensis follows this acoustical principle of combining simple sources, and discuss the acoustical basis of a sonar transmitter of an echolocating bat with a nostril emitter.…”