High resolution acoustic measurement system and beam pattern reconstruction method for bat echolocation emissions.
Measurements of the transmit beam patterns emitted by echolocating bats have previously been limited to cross-sectional planes or averaged over multiple signals using sparse microphone arrays. To date, no high-resolution measurements of individual bat transmit beams have been reported in the literature. Recent studies indicate that bats may change the time-frequency structure of their calls depending on the task, and suggest that their beam patterns are more dynamic than previously thought. To investigate beam pattern dynamics in a variety of bat species, a high-density reconfigurable microphone array was designed and constructed using low-cost ultrasonic microphones and custom electronic circuitry. The planar array is 1.83 m wide by 1.42 m tall with microphones positioned on a 2.54 cm square grid. The system can capture up to 228 channels simultaneously at a 500 kHz sampling rate. Beam patterns are reconstructed in azimuth, elevation, and frequency for visualization and further analysis. Validation of the array measurement system and post-processing functions is shown by reconstructing the beam pattern of a transducer with a fixed circular aperture and comparing the result with a theoretical model. To demonstrate the system in use, transmit beam patterns of the big brown bat, Eptesicus fuscus, are shown.
Naval Undersea Warfare Center, Newport, Rhode Island 02841.
Jason E
JE
Gaudette
Department of Neuroscience, Brown University, Providence, Rhode Island 02912.
Laura N
LN
Kloepper
Department of Neuroscience, Brown University, Providence, Rhode Island 02912.
Michaela
M
Warnecke
Department of Neuroscience, Brown University, Providence, Rhode Island 02912.
James A
JA
Simmons
D000162:Acoustics / Q000295:instrumentation; D000818:Animals; D002685:Chiroptera / Q000145:classification / Q000502:physiology / Q000523:psychology*; D004455:Echolocation; D004867:Equipment Design; D008962:Models, Theoretical; D010363:Pattern Recognition, Automated; D015203:Reproducibility of Results; D012815:Signal Processing, Computer-Assisted; D013997:Time Factors; D014159:Transducers; D014828:Vocalization, Animal