Beamwidth in bat biosonar and man-made sonar

Abstract

Beamwidth measures how a sonar system distributes emitted energy or receiver sensitivity over angle. For man-made sonars, this is considered to be of critical importance, since a small beamwidth supports high-resolution imaging. For bat biosonar, the role of beamwidth is far less clear. In order to investigate how biosonar beamwidths could compare to its man-made peers, we have compiled beamwidth data for bats (based on numerical predictions) and man-made sonar systems (based on data sheets). An analysis of this data shows that bat biosonar and man-made sonars operate in very different regimes with respect to the ratio of characteristic dimension (i.e., aperture diameter for bats and array length for man-made sonars) to wavelength. Whereas the aperture diameters of bats ranged from falling below the employed wavelength to being about 10 times larger, man-made sonars were typically at least one order of magnitude larger than the employed wavelengths and ranged up to 1000 times larger. Furthermore, for any given characteristic-dimension-to-wavelength ratio, bats showed much more variability in beamwidth than man-made sonar. In fact, the variability in the bat beamwidths was found to be as large as that in a set of random horns, which indicates a role for other determining factors.Beamwidth measures how a sonar system distributes emitted energy or receiver sensitivity over angle. For man-made sonars, this is considered to be of critical importance, since a small beamwidth supports high-resolution imaging. For bat biosonar, the role of beamwidth is far less clear. In order to investigate how biosonar beamwidths could compare to its man-made peers, we have compiled beamwidth data for bats (based on numerical predictions) and man-made sonar systems (based on data sheets). An analysis of this data shows that bat biosonar and man-made sonars operate in very different regimes with respect to the ratio of characteristic dimension (i.e., aperture diameter for bats and array length for man-made sonars) to wavelength. Whereas the aperture diameters of bats ranged from falling below the employed wavelength to being about 10 times larger, man-made sonars were typically at least one order of magnitude larger than the employed wavelengths and ranged up to 1000 times larger. Furthermore, for any ...