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The sound field distribution in the vocal tract with a single sound source in the glottis and the transfer function of the supraglottal vocal tract of the horseshoe bat, Rhinolophus pusillus, have been obtained using the finite-element method (FEM) technique. The models of vocal tracts used for FEM calculation are constructed by tomography scanning. These models are used to set up a finite-element model for calculating the sound field distribution by loading the unit sound source in the glottis. By changing the frequency of the unit sound source, the frequency response was figured out and the acoustic role of vocal tract chambers was examined by obtaining the transfer function and sound pressure distribution before and after filling the chambers using voxels. Sound pressures in the trachea and nostrils are recorded and some analysis of the acoustics of the subglottal and vocal tract was made to find the function of the construction in the vocal tract and subglottal parts. The results show nasal chambers can effectively improve the Q (quality factor) value near the second harmonic, and alternate the sound distribution in the supraglottal part. Whereas the tracheal chambers can reduce the amplitude second harmonic in the subglottal part, its function is like a notch filter which can block the second harmonic component of the back propagation sound under the glottis.

Horseshoe bats emit biosonar pulses through the nostrils and diffract the outgoing ultrasonic pulses with baffles, so-called “noseleaves,” that surround the nostrils. The noseleaves have complex static geometries and can furthermore undergo dynamic shape changes during emission of the biosonar pulses. The posterior noseleaf part, the lancet, has been shown to carry out anterior-posterior flicking motions during biosonar emissions with average lancet tip displacements of about 1 mm. Here, the acoustic effects of the interplay between the lancet furrows and shape change (lancet rotation) on the emission beam were investigated using the animated digital models obtained from the noseleaves of greater horseshoe bats (Rhinolophus ferrumequinum). It was found that forward lancet rotations increase the amount of sound energy allocated to secondary amplitude maxima (sidelobes) in the beampattern, but only in the presence of the furrows. The interaction between static and dynamic features can be readily quantified by roughness (standard deviation about local mean) of the amplitude distribution of the beampatterns. This effect goes beyond the static impact of the furrows on the width of the mainlobe. It could allow the bats to send out their pulses through a sequence of qualitatively different beampatterns.

Horseshoe bats have to navigate through complex environments such as dense forests and structure-rich vegetation relying on input from their highly sophisticated biosonar systems. One of the key components of these bats' ability to obtain high-quality acoustic information is to alter the shape of their outer ears rapidly. In prior work, the authors have shown that by mimicking the horseshoe bat rapid ear movements, a bat-inspired robotic dynamic periphery for recording speech signals could enhance speech recognition for limited dataset and also provide estimates for the speaker's direction along with speech recognition. In our current study, we continued to investigate how speech datasets processed by the dynamic periphery may be enhanced compared to a reference by extracting acoustical features through Mel frequency cepstral coefficient (MFCC) transform, Lyon's cochlear bandpass filters, and a neural spike representation, respectively. This study aims to characterize the detailed acoustical differences and quantify the improved speaker intelligence with noise robustness through the dynamic periphery. The ultimate goal of this research is to identify a signal representation that is well suited to capitalize on the time-variant properties of the biomimetic recording periphery and make the dynamic information-bearing features accessible for the classification stages.Horseshoe bats have to navigate through complex environments such as dense forests and structure-rich vegetation relying on input from their highly sophisticated biosonar systems. One of the key components of these bats' ability to obtain high-quality acoustic information is to alter the shape of their outer ears rapidly. In prior work, the authors have shown that by mimicking the horseshoe bat rapid ear movements, a bat-inspired robotic dynamic periphery for recording speech signals could enhance speech recognition for limited dataset and also provide estimates for the speaker's direction along with speech recognition. In our current study, we continued to investigate how speech datasets processed by the dynamic periphery may be enhanced compared to a reference by extracting acoustical features through Mel frequency cepstral coefficient (MFCC) transform, Lyon's cochlear bandpass filters, and a neural spike representation, respectively. This study aims to characterize the detailed acoustical differences a...

Horseshoe bat biosonar is characterized by a pronounced dynamics at the interfaces of ultrasound emission and reception: The bats can alter the shapes of their noseleaves and outer ears (pinnae) through muscular action while they are emitting or receiving biosonar signals. An information-theoretic analysis has been conducted to assess whether these non-rigid baffle motions could affect the ability of the bats' biosonar system to encode sensory information. This analysis was based on acoustic characterizations (beampatterns) obtained either through numerical predictions or from measurements of physical models. In total, four time-variant baffle shapes, for emission and reception, numerical and physical each, have been analyzed. The similarity of beampattern across different baffle shape conformations was quantified using normalized mutual information that was found to be

Bats have evolved unique mechanisms by which to navigate and hunt in their environments. Some species of the microchiroptera, such as members of the horseshoe bat family (Rhinolophidae), which live in particularly challenging, cluttered environments, have been observed to move their peripheral structures for emission and reception (noseleaf and pinna) during echolocation very rapidly, e.g., within a tenth of a second. With these behaviors, the bats could create time-variant properties in their biosonar systems to provide additional degrees of freedom to be used for enhancing the encoding of sensory information. To make full use of this opportunity, a tight sensorimotor integration is likely to be required. In order to explore the possible role of sensorimotor integration in a dynamic biosonar system, we have developed biomimetic robotic models to replicate the effects of the dynamics of the baffle structures. Data obtained with these systems indicates that a coordinated emitter and receiver dynamics can b...

Echolocation signals of horseshoe bats (Rhinolophidae) consist of a relatively long component of constant frequency (CF) which is preceded by an initial frequency-modulated (iFM) component and followed by a terminal frequency-modulated (tFM) component. To examine the role of these components in echolocation, four bats were trained to fly from a perch to a landing bar. A dual camera system allowed reconstruction of the flight paths in three dimensions. Echolocation signals were recorded, analyzed, and correlated with the flight behavior of the bats. It was confirmed that during flight the bats compensate the Doppler shifts which are produced by their own flight movement. In free flight they emit per wing beat one single signal of long duration, with little variation in the three signal components. In approach flight the bats reduce pulse duration and interval with decreasing target range. The iFM is not varied with respect to target range, suggesting that this component plays little role in the processing of echolocating a target of interest. The bandwidth of the tFM component is increased while its duration is shortened in proportion to decreasing target range, so that the signal-echo overlap of the FM component is avoided down to a target distance of 15 cm. These concurrent changes suggest that the tFM component is used for ranging. During the last 60 cm of the approach the bats compensated for the increase of echo SPL by lowering the emission level of the CF component by 6-9 dB and that of the tFM component by 9-11 dB per halving of range. The specific signal structure of horseshoe bats is discussed as an adaptation for the hunting of fluttering insects in highly cluttered environments.

Horseshoe bats can alter the shape of noseleaves and outer ears (pinnae) at the time of emission and reception of biosonar pulses. The shape changes are a result of specific muscular action and significantly change the emission and reception beams by a spatial redistribution of energy in mainlobe and sidelobes. Here, we explore the potential of embedding dynamic features into the speech signals by means of bat inspired reception dynamics to improve the speech recognition accuracy and speaker localization. For this analysis, a digit dataset with 11 U.S. English speakers was recorded through a robotic setup that mimics pinna dynamics as observed in bats. The utterances were obtained through open-source speech corpora and amplitude modulated (carrier frequency: 55 kHz) to shift to ultrasonic band. These utterances were then re-recorded through the dynamic pinna set up and later demodulated to extract the original signal. It was found that reception dynamics have been able to enrich the speech signals with dynamic, direction-dependent time-frequency patterns. The next step in this research is to assess whether these patterns can be utilized to improve speech recognition and speaker localization.

Echolocating bats can fly without colliding with obstacles by synchronizing acoustic guidance and flight control. To research how bats adapt echolocation as they became familiar with the spaces, we made CF-FM bats (Japanese horseshoe bat) exhibit S-sharp flight repeatedly in a chamber arranged acoustically transparent chains. We found (1) flight path was changed continuously to reduce its curvature as the bats repeated the flights, resulting that the maximum flight speed increased from 2.7 to 3.0 m/s in the 1st trial to 3.2 to 3.8 m/s in the 12th (last) trial for all three bats, (2) pulse emission was reduced by 45% (66/148 pulses) from the first to the last trial, (3) they shifted the pulse direction dynamically relative to their flight direction in the 1st flight whereas the pulse direction was shifted smoothly, the bats emitted more intense pulses toward the intended flight direction as they became familiar with the space. When acrylic boards were arranged, the bats could not pass through the obstacle ...

Research with behaving horseshoe bats has suggested that the animals' biosonar system is characterized by pervasive dynamics at the interfaces for ultrasound emission and reception. Baffle shapes that diffract the outgoing and incoming ultrasonic pulses change their geometries during emission and reception. However, it remains unclear if and how this dynamics could affect the function of bats' biosonar system. To investigate this question, biomimetic reproduction of this peripheral dynamics have been used to obtain system characterizations as well as echo recordings. The data obtained with these biomimetic sonar systems have yielded the following key results: If the static and dynamic geometries of the diffracting baffles as well as their coupling to the transducers is suitable, time-variant device characteristics can be produced—even for small and geometrically simple changes to the shapes. These characteristics depend on direction and frequency (like a static beampattern) as well as on time. Furthermore...

This study describes variation patterns in the constant frequency of echolocation calls emitted at rest and when not flying (“resting frequency” RF) of the least horseshoe bat, Rhinolophus pusillus, on a broad geographical scale and in response to local climatic variables. Significant differences in RF were observed among populations throughout the species range in Mainland China, and this variation was positively and significantly related to climate conditions, especially environmental humidity, but the variability was only weakly associated with geographical distance. Sex dimorphism in the RF of R. pusillus may imply that female and male might keep their frequencies within a narrow range for sex recognition. Moreover, bats adjusted resting frequency to humidity, which may imply partitioning diet by prey size or the influence of rainfall noise. The results indicate that bats adjust echolocation call frequency to adapt to environmental conditions. Therefore, environmental selection shape the diversity of echolocation call structure of R. pusillus in geographically separated populations, and conservation efforts should focus on changes in local climate and effects of environmental noise.

Horseshoe bat noseleaves are intricate baffle structures that diffract the animals' ultrasonic biosonar pulses upon emission. Furthermore, horseshoe bats dynamically change the shapes of their noseleaves through muscular actuation. Motions have been previously described for two lancet parts, anterior leaf and lancet. In both cases, the observed motions resulted in changes to the opening angle of the noseleaf baffle. Here, experiments were carried out with simplified baffle shapes that mimic the dynamics seen in horseshoe bats. For the baffle walls to have an effect on the outgoing wavefields, the sound outlets have to be narrow at least in one direction so that their near-fields generate substantial sound pressure amplitudes on the surface of the baffle. The baffle geometry was found to play an important role in the generation of dynamic signatures in the emitted pulses. As the opening of the baffle was varied by small increments, concave baffle surfaces were found to result in much larger dynamic changes to the beampatterns than straight baffles surfaces. Hence, concave baffles were able to introduce large dynamic signatures into the pulses even for small changes in opening angles. This may match the situation in horseshoe bats where the concerned baffles are also concave.

The periphery of the biosonar system of horseshoe bats is characterized by a conspicuous dynamics where the shapes of the noseleaves (structures that surround the nostrils) and the outer ears (pinnae) undergo fast changes that can coincide with pulse emission and echo reception. These changes in the geometries of the sound-reflecting surfaces affect the device characteristics, e.g., as represented by beampatterns. Hence, this dynamics could give horseshoe bats an opportunity to view their environments through a set of different device characteristics. It is not clear at present whether horseshoe bats make use of this opportunity, but there is evidence from various sources, namely, anatomy, behavior, evolution, and information theory. Anatomical studies have shown the existence of specialized muscular actuation systems that are clearly directed toward geometrical changes. Behavioral observations indicate that these changes are linked to contexts where the bat is confronted with a novel or otherwise demanding situation. Evolutionary evidence comes from the occurrence of qualitatively similar ear deformation patterns in mustached bats (Pteronotus) that have independently evolved a biosonar for Doppler-shift detection. Finally, an information-theoretic analysis demonstrates that the capacity of the biosonar system for encoding sensory information is enhanced by these dynamic processes.

Horseshoe bats (family Rhinolophidae) have evolved a capable biosonar system to allow the pursuit of prey amid dense vegetation that produces large amounts of clutter echoes. Horseshoe bats have long been known to employ dynamic effects such as Doppler effect compensation and large-scale rotations of their pinnae to realize these capabilities. Recent research has produced evidence of even more pervasive dynamical biosonar properties in horseshoe bat biosonar as well as in the related Old World leaf-nosed bats (family Hipposideridae). On the emission side, these animals employ elaborate baffle shapes that surround the exit points of their ultrasonic pulses (nostrils). During echolocation, multiple parts of these noseleaves such as the anterior leaf and the lancet in horseshoe bats are set in motion, typically in synchrony with pulse emission, hence creating a time-variant channel for the exiting wave packets. Similarly, the pinnae which diffract the incoming echoes on the reception side are frequently in motion while echoes impinge on them. These motions include non-rigid changes in shape. All these effects add a dynamic dimension to the interface of the bats' biosonar with the external world, which could allow the animals to enhance the quantity and quality of the sensory information they receive.

Glenis and I were psychology graduate students together in 1970-1971. She was interested in auditory psychophysics, but soon developed an interest in comparative psychophysics which she pursued in a post-doc and a faculty position in Germany, where she obtained a behavioral audiogram for the horseshoe bat and later studied masking in the same species. This audiogram was one of the very first psychophysical investigations of hearing in any bat and the very first for the horseshoe bat. It confirmed a rather complex frequency response function with sensitivity peaks at about 20 kHz and 60 kHz, and a very sharp peak at about 80 kHz. The masked thresholds indicated rather normal critical masking ratios (CR) except in a narrow region at about 80 kHz where the CRs are up to 15 dB lower than expected, suggesting a critical band of about 300 Hz at 80 kHz that is presumably used in Doppler-shift compensation. In 1981-1983, Glenis went on to investigate frequency and rate modulation discrimination in the chinchilla, for the first time, and to study tone-on-tone masking in the chinchilla. Since these early works, Glenis has maintained her comparative interests with studies on birds, kangaroo rats, frogs, and fleas on cats.

Horseshoe bats are known to exhibit non-rigid pinna deformations as part of their biosonar behaviors. During these deformation cycles, the pinnae of the animals alternate between upright and bent shape configurations that differ in their overall geometry as well as in the shapes and relative positions of local shape features. Artificial baffle prototypes have been designed to emulate these deforming bat pinnae. The prototype shapes were designed by augmenting an obliquely truncated cone with biomimetic local shape features. The prototype was implemented using elastic (synthetic rubber) materials. The deformation of the structure was accomplished through a simple actuation mechanism that was inserted on the back side of the artificial pinna. Features of the horseshoe bat pinna that have been evaluated for this study include a prominent vertical ridge that runs along the entire inner pinna surface, the antitragus along with the lateral incisions that separate it from the back portion of the pinna, and a pin...

Many bat species exhibit conspicuous ear movements as part of their biosonar behaviors. The resulting transformations of the pinnae can contain rigid rotations as well as nonrigid deformations. Characteristic ear deformations are frequently observed in horseshoe bats (Rhinolophidae). In these animals, the pinna changes regularly between an upright and a bent configuration. In the bent configuration, the tip of the pinna tilts forward, down, and sideways, changing the curvature of large portions of the ear surface. Entire deformation cycles can be completed in as little as 200 ms. The time‐variant geometry of the pinna deformations in the greater horseshoe bat (Rhinolophus ferrumequinum) was captured with a stereo pair of high‐speed video cameras. Landmark points were marked on the pinna with dyes that were equally visible in the video frames as in x‐ray micro‐CT. The CT model was matched to the locations of the landmarks in the deforming ears inferred from stereo reprojection. Numerical predictions were obtained for the acoustic behavior of ear shapes at different phases during the deformation cycle. It was found that the pinna deformations seen in the animals can produce large changes in the directivity patterns. [Work supported by NSFC (Project No. 10774092) and CSC.]

Horseshoe bats emit their biosonar pulses through nostrils that are surrounded by elaborate baffle shapes (noseleaves). The shape and size of the different noseleaf shape elements can vary considerably between species. Here, the acoustic effects of the length of the sella have been investigated based on the noseleaf of Bourret’s Horseshoe Bat (Rhinolophus paradoxolophus) which features an exceptionally long sella: High‐resolution digital representations of the noseleaves of three specimens were used to vary the sella length below and above its natural value. A principal axis through the sella was used to define the direction of this scaling. The acoustic beamforming properties of the noseleaf were then assessed as a function of sella scale using numerical methods. It was found that elongating the sella narrows the biosonar beam of the second harmonic in elevation. Furthermore, the natural length of the sella in Bourret’s Horseshoe Bat coincided with a fiducial point in the relationship between sella lengt...

Most animals constantly adjust the spectrotemporal composition of their vocalizations depending on the information content intended to be conveyed by these signals. Whereas most studies focus on the sensory processing of spectrotemporal features of vocalizations in various vertebrates, it is still widely unknown how vocal motor structures in the brain adjust these call parameters. We used echolocation and acoustic communication behaviors in horseshoe bats to analyze the neurobiological and biomechanical basis for the motor control of their vocalizations. Results from pharmacological studies of the vocal motor nucleus, the nucleus ambiguus, lead us to developed a novel model for call frequency control by vocal motor neurons. Neurophysiological recordings combined with pharmacological manipulations at the single cell level in spontaneously vocalizing bats substantiated this model. Biomechanical properties of the larynx were also found to aid in call frequency control: Altering tracheal air flow in an isolated larynx preparation resulted in two distinct frequency bands that were non‐harmonically related and reflected the main frequency components of echolocation pulses and communication signals, respectively. In addition, changes in air pressure revealed transitions from periodic to chaotic that occurred within a single signal cycle, giving rise to spectral features observed in horseshoe bat communication signals.

Memories and Reflections on Biosonars.- Section 1: Echolocation Signals and Their Production.- Echolocation Signal Types of Odontocetes.- The Production of Echolocation Signals by Bats and Birds.- Propagation of Beluga Echolocation Signals.- Nasal Pressure and Sound Production in an Echolocating White Whale, Delphinapterus leucas.- The Study of the Sound Production Apparatus in the Harbour Porpoise, Phocoena phocoena, and the Jacobita, Cephalorhynchus commersoni by Means of Serial Cryo-Microtome Sectioning and 3-D Computer Graphics.- The Anatomy of Acoustic Structures in the Spinner Dolphin Forehead as Shown by X-Ray Computed Tomography and Computer Graphics.- Whale Heads, Magnetic Resonance Images, Ray Diagrams and Tiny Bubbles.- Individual Variation in Vocal Tract Resonance May Assist Oilbirds in Recognizing Echoes of Their Own Sonar Clicks.- Midbrain Areas as Candidates for Audio-Vocal Interface in Echolocating Bats.- The Sounds of Sperm Whale Calves.- Apparent Sonar Clicks from a Captive Bottlenosed Dolphin, Tursiops truncatus, When 2, 7 and 38 Weeks Old.- Ontogeny of Vocal Signals in the Big Brown Bat, Eptesicus fuscus.- Observations on the Development of Echolocation in Young Bottlenose Dolphins.- The Short-Time-Duration Narrow-Bandwidth Character of Odontocete Echolocation Signals.- Section 2: Auditory Systems of Echolocating Animais.- Parallel-Hierarchical Processing of Biosonar Information in the Mustached Bat.- Dolphin Echolocation and Audition.- Parallel Auditory Pathways I: Structure and Connections.- Parallel Auditory Pathways II: Functional Properties.- Cochlear Physiology and Anatomy in Bats.- Ascending Pathways to the Inferior Colliculus via the Superior Olivary Complex in the Rufous Horseshoe Bat, Rhinolophus rouxii.- Pattern of Projections to the 60 KHz Isofrequency Region of the Mustache Bat's Inferior Colliculus.- Target Range Processing Pathways in the Auditory System of the Mustached Bat.- Processing of Paired Biosonar Signals in the Cortices of Rhinolophus rouxi and Pteronotus P. parnellii: A Comparative Neurophysiological and Neuroanatomical Study.- Central Control of Frequency in Biosonar Emissions of the Mustached Bat.- Frontal Auditory Space Representation in the Cerebellar Vermis of Echolocating Bats.- Directional Emission and Time Precision as a Function of Target Angle in the Echolocating Bat Carollia perspicillata.- The Jaw-Hearing Dolphin: Preliminary Behavioral and Acoustical Evidence.- Acoustical Aspects of Hearing and Echolocation in Bats.- The Perception of Complex Echoes by an Echolocating Dolphin.- Morphometric Analysis of Cochlear Structures in the Mustached Bat, Pteronotus p. parnellii.- The Efferent Auditory System in Doppler-Shift Compensating Bats.- Some Comparative Aspects of Auditory Brainstem Cytoarchitecture in Echolocating Mammals: Speculations on the Morphological Basis of Time-Domain Signal Processing.- Temporal Order Discrimination within the Dolphin Critical Interval.- Detection Abilities and Signal Characteristics of Echolocating False Killer Whales (Pseudorca crassidens).- Binaural Neurons in the Mustache Bat's Inferior Colliculus: Physiology, Functional Organization, and Behavioral Implications.- Ontogeny of the Echolocation System in Rhinolophoid CF-FM Bats: Audition and Vocalization in Early Postnatal Development.- Lightmicroscopic Observation of Cochlear Development in Horseshoe Bats (Rhinolophus rouxi).- Only One Nucleus in the Brainstem Projects to the Cochlea in Horseshoe Bats: The Nucleus Olivo-Cochlearis.- Section 3: Performance of Animal Sonar Systems.- The Performance of Echolocation: Acoustic Images Perceived by Echolocating Bats.- Designing Critical Experiments on Detection and Estimation in Echolocating Bats.- Target Discrimination and Target Classification in Echolocating Bats.- Target Detection by Echolocating Bats.- Sonar Target Detection and Recoginition by Odontocetes.- Prey Interception: Predictive and Nonpredictive Strategies.- A Mechanism for Horizontal and Vertical Target Localization in the Mustache Bat (Pteronotus p. parnellii).- Echoes of Fluttering Insects.- Encoding of Natural Insect Echoes and Sinusoidally Modulated Stimuli by Neurons in the Auditory Cortex of the Greater Horseshoe Bat, Rhinolophus ferrumeauinum.- Do Signal Characteristics Determine a Bat's Ability to Avoid Obstacles?.- Greater Horseshoe Bats Learn to Discrimate Simulated Echoes of Insects Fluttering with Different Wingbeat Rates.- Predictive Tracking of Horizontally Moving Targets by the Fishing Bat, Noctilio leporinus.- Discrimination of Target Surface Structure in the Echolocating Bat, Megaderma lyra.- A Time Window for Distance Information Processing in the Bats, Noctilio albiventris and Rhinolophus rouxi.- Section 4: Natural History of Echolocation.- Natural History Aspects of Marine Mammal Echolocation: Feeding Strategies and Habitat.- Behaviour and Foraging Ecology of Echolocating Bats.- Interaction between Echolocating Bats and Their Prey.- Loud Impulse Sounds in Odontocete Predation and Social Behavior.- Harmonic Structure of Bat Echolocation Signals.- Acoustical VS. Visual Orientation in Neotropical Bats.- Echolocation Strategies of Aerial Insectivorous Bats and Their Influence on Prey Selection.- Foraging Behavior, Prey Selection and Echolocation in Phyllostomine Bats (Phyllostomidae).- Variation in Foraging Strategies in Five Species of Insectivorous Bats - Implications for Echolocation Call Design.- Detection of Prey in Echocluttering Environments.- How the Bat, Pipistrellus kuhli Hunts for Insects.- The Communication Role of Echolocation Calls in Vespertilionid Bats.- Auditory Input to the Dorsal Longitudinal Flight Motor Neurons of a Noctuid Moth.- Disrupting Foraging Bats: The Clicks of Arctiid Moths.- The Echolocation Assemblage: Acoustic Ensembles in a Neotropical Habitat.- Microbat Vision and Echolocation in an Evolutionary Context.- Future Directions.- Section 5: Echolocation and Cognition.- On the Evolution of Acoustic Communication Systems in Vertebrates Part I: Historical Aspects.- On the Evolution of Acoustic Communication Systems in Vertebrates Part II: Cognitive Aspects.- Cognitive Aspects of Echolocation.- Cognition and Echolocation of Dolphins.- Loud Sounds during Feeding in Indian Ocean Bottlenose Dolphins.- Attention and Detection in Dolphin Echolocation.- Odontocete Sonar Systems Research - Future Directions from a Ethologist's Personal Point of View.- Section 6: Echolocation Theory and Applications.- Some Theoretical Concepts for Echolocation.- Detection and Recognition Models of Dolphin Sonar Systems.- A Brief History of Bionic Sonars.- Biosonar Signal Processing Applications.- Take off Signals Emitted by Myotis mystacinus: Theory of Receivers and Modelling.- Noseleaves and Bat Pulses.- Time-Frequency Processing of Bat Sonar Signals.- Echoes from Insects Processed Using Time Delayed Spectrometry (TDS).- Sonar Discrimination of Metallic Plates by Dolphins and Humans.- Echoes from Solid and Hollow Metallic Spheres.- Target Identification in a Natural Environment: A Statistical View of the Inverse Problem.- An Automatic Target Recognition Algorithm Using Time-Domain Features.- A Matched Filter Bank for Time Delay Estimation in Bats.- Participants.

Six Rhinolophus ferrumequinum were trained to fly through an array of vertical or horizontal wires. Obstacle avoidance performance was measured as the percentage of flights in which the bats did not touch the wires (successful flights). Bats with normal mobile pinnae scored between 70% and 90% successful flights both with vertical and horizontal wires. After surgically immobilizing the pinnae by cutting motor nerves and ear muscles, avoidance performance with vertical wires (horizontal target localization) was unchanged but the percentage of successful flights with horizontal wires (vertical target localization) decreased significantly. This demonstrates the importance of pinna movements for target localization in the vertical plane and supports the hypothesis that scanning movements with pinnae are used by Rhinolophus ferrumequinum for determination of target angle.

The transfer function of the supraglottal vocal tract of the horseshoe bat, Rhinolophus hildebrandti, was obtained by a noninvasive technique, based on incremental variations in the helium content of inspired gas, which also allowed the source spectrum to be determined. The acoustic role of the vocal tract chambers was examined by obtaining the transfer function before and after filling the chambers. Simultaneous recording of sound pressures in the trachea during these experiments allowed some analysis of subglottal acoustics. With the vocal tract intact, the transfer function was found to show sharp transmission minima at the fundamental and third harmonic and a broad transmission maximum at the emitted second harmonic. This transfer function shape, along with the source spectrum obtained, demonstrates that the second harmonic dominance in the emitted pulse is achieved by vocal tract filtering, although the source spectrum is different from that typical of man in that it does not show an f−2 harmonic dec...

The horseshoe bat, Rhinolophus ferrumequinum, emits sonar cries that rise slightly in frequency to about 83 kHz, remain constant at 83 kHz for 10–50 msec or so, and then during the last millisecond or two sweep downward to 65 or 70 kHz. Other laboratories have reported that the bat adjusts its outgoing CW frequency to keep the returning echo frequency at 83.4 kHz regardless of Doppler shift. Discrimination experiments indicate that Rhinolophus uses the terminal FM signal for target ranging, achieving an acuity of about 30 mm with a cross‐correlation sonar receiver. The FM and CW signals are separated by sharply tuned auditory mechanisms into different populations of neurons. Such separation is vital in a correlation receiver to prevent contamination of the FM signal with the CW signal and consequent loss of acuity in ranging. Doppler‐shift compensation is necessary because the narrow‐band FM waveform of Rhinolophus is subject to intolerably large Doppler ranging errors. Other bats that use correlation receivers avoid severe Doppler ranging errors by transmitting broad‐band FM signals.