Wireless recording of the calls of Rousettus aegyptiacus and their reproduction using electrostatic transducers

Bats are capable of imaging their surroundings in great detail using echolocation. To apply similar methods to human engineering systems requires the capability to measure and recreate the signals used, and to understand the processing applied to returning echoes. In this work, the emitted and reflected echolocation signals of Rousettus aegyptiacus are recorded while the bat is in flight, using a wireless sensor mounted on the bat. The sensor is designed to replicate the acoustic gain control which bats are known to use, applying a gain to returning echoes that is dependent on the incurred time delay. Employing this technique allows emitted and reflected echolocation calls, which have a wide dynamic range, to be recorded. The recorded echoes demonstrate the complexity of environment reconstruction using echolocation. The sensor is also used to make accurate recordings of the emitted calls, and these calls are recreated in the laboratory using custom-built wideband electrostatic transducers, allied with a spectral equalization technique. This technique is further demonstrated by recreating multi-harmonic bioinspired FM chirps. The ability to record and accurately synthesize echolocation calls enables the exploitation of biological signals in human engineering systems for sonar, materials characterization and imaging

Evolutionary origins of ultrasonic hearing and laryngeal echolocation in bats inferred from morphological analyses of the inner ear

PMCID: PMC3598973This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited

Laryngeal Nerve Activity During Pulse Emission in the CF-FM Bat, Rhinolophus ferrumequinum. I. Superior Laryngeal Nerve (External Motor Branch)

The activity of the external (motor) branch of the superior laryngeal nerve (SLN), innervating the cricothyroid muscle, was recorded in the greater horseshoe bat,Rhinolophus ferrumequinum. The bats were induced to change the frequency of the constant frequency (CF) component of their echolocation signals by presenting artificial signals for which they Doppler shift compensated. The data show that the SLN discharge rate and the frequency of the emitted CF are correlated in a linear manner

Neural control of vocalization in bats: mapping of brainstem areas with electrical microstimulation eliciting species-specific echolocation calls in the rufous horseshoe bat

1. The functional role of brainstem structures in the emission of echolocation calls was investigated in the rufous horseshoe bat, Rhinolophus rouxi, with electrical low-current microstimulation procedures. 2. Vocalizations without temporal and/or spectral distortions could be consistently elicited at low threshold currents (typically below 10 A) within three clearly circumscribed brainstem areas, namely, the deep layers and ventral parts of the intermediate layers of the superior colliculus (SC), the deep mesencephalic nucleus (NMP) in the dorsal and lateral midbrain reticular formation and in a distinct area medial to the rostral parts of the dorsal nucleus of the lateral lemniscus. The mean latencies in the three vocal areas between the start of the electrical stimulus and the elicited vocalizations were 47 msec, 38 msec and 31 msec, respectively. 3. In pontine regions and the cuneiform nucleus adjacent to these three vocal areas, thresholds for eliciting vocalizations were also low, but the vocalizations showed temporal and/or spectral distortions and were often accompanied or followed by arousal of the animal. 4. Stimulus intensity systematically influenced vocalization parameters at only a few brain sites. In the caudo-ventra1 portions of the deep superior colliculus the sound pressure level of the vocalizations systematically increased with stimulus intensity. Bursts of multiple vocalizations were induced at locations ventral to the rostral parts of the cuneiform nucleus. No stimulus-intensity dependent frequency changes of the emitted vocalizations were observed. 5. The respiratory cycle was synchronized to the electrical stimuli in all regions where vocalizations could be elicited as well as in more ventrally and medially adjacent areas not yielding vocalizations on stimulation. 6. The possible functional involvement of the vocal structures in the audio-vocal feedback system of the Dopplercompensating horseshoe bat is discussed

Acoustic behavior of melon-headed whales varies on a diel cycle.

Many terrestrial and marine species have a diel activity pattern, and their acoustic signaling follows their current behavioral state. Whistles and echolocation clicks on long-term recordings produced by melon-headed whales (Peponocephala electra) at Palmyra Atoll indicated that these signals were used selectively during different phases of the day, strengthening the idea of nighttime foraging and daytime resting with afternoon socializing for this species. Spectral features of their echolocation clicks changed from day to night, shifting the median center frequency up. Additionally, click received levels increased with increasing ambient noise during both day and night. Ambient noise over a wide frequency band was on average higher at night. The diel adjustment of click features might be a reaction to acoustic masking caused by these nighttime sounds. Similar adaptations have been documented for numerous taxa in response to noise. Or it could be, unrelated, an increase in biosonar source levels and with it a shift in center frequency to enhance detection distances during foraging at night. Call modifications in intensity, directionality, frequency, and duration according to echolocation task are well established for bats. This finding indicates that melon-headed whales have flexibility in their acoustic behavior, and they collectively and repeatedly adapt their signals from day- to nighttime circumstances

Hearing and Echolocation in the Australian Grey Swiftlet, Collocalia Spodiopygia

The frequency sensitivity of hearing in the grey swiftlet, Collocalia spodiopygia, was determined by neuronal recordings from the auditory midbrain (MLD). The most sensitive best frequency response thresholds occurred between 0.8 and 4.7 kHz, with the upper frequency limit near 6 kHz. Spectral analysis of echolocation click pairs revealed energy peaks between 3.0 and 8.0kHz for the foreclick, compared to 4.0-6.0 kHz for the principal click. The relationship between good hearing sensitivity and click energy peaks in the swiftlet extends about an octave higher than it does in the oilbird (Steatornis caripensis)