On-board telemetry of emitted sounds from free-flying bats: compensation for velocity and distance stabilizes echo frequency and amplitude

Hiryu, Shizuko; Yu, Suzhu; Hosokawa, Tatsuro; Riquimaroux, Hiroshi; Watanabe, Yoshiaki

doi:10.1007/s00359-008-0355-x

Cited by 75 publications

(63 citation statements)

References 35 publications

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“…2 H and I). We conclude, first, that these frequency shifts result from the bat's response, because the miniature microphone in the Telemike system protrudes forward from the Telemike circuit board on the bat's back and neck to occupy a recording position slightly forward of the external ears and just above the bat's open mouth (15)(16)(17). This location serves as a constant acoustic "vantage point" for measuring changes in FM1, so that the observed frequency differences can be attributed reasonably to the bat's vocalizations themselves.…”

Section: Discussionmentioning

confidence: 91%

“…Here, we combine two recently introduced experimental methodsradio telemetry of sounds from the flying bat for very stable recording of the transmitted signals (15)(16)(17) in tandem with flight tests using an extended array of obstacles during which bats emit sounds at sufficiently short IPIs to create the conditions for ambiguity (12). The bat's response to ambiguity caused by overlap of extended echo streams is specific: Whenever ambiguity occurs (IPIs shorter than ESDs), the bat shifts the frequencies of the FM sweep upward in the first broadcast and downward in the second broadcast by several kilohertz (ΔF) in proportion to the degree of overlap (IPI minus ESD).…”

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confidence: 99%

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FM echolocating bats shift frequencies to avoid broadcast–echo ambiguity in clutter

Hiryu

Bates²,

Simmons

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

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Sonar broadcasts are followed by echoes at different delays from objects at different distances. When broadcasts are emitted rapidly in cluttered surroundings, echo streams from successive broadcasts overlap and cause ambiguity in matching echoes to corresponding broadcasts. To identify reactions to ambiguity in clutter, echolocating bats that emit multiple-harmonic FM sounds were trained to fly into a dense, extended array of obstacles (multiple rows of vertically hanging chains) while the sonar sounds the bat emitted were recorded with a miniature radio microphone carried by the bat. Flight paths were reconstructed from thermal-infrared video recordings. Successive rows of chains extended more than 6 m in depth, so each broadcast was followed by a series of echoes from multiple rows of chains that lasted up to 40 ms. Bats emitted sounds in pairs ("strobe groups") at short (20-40 ms) interpulse intervals (IPIs) alternating with longer IPIs (>50 ms). For many short IPIs, the stream of echoes from the first broadcast was still arriving when the second broadcast was emitted. This overlap caused ambiguity about matching echoes with broadcasts. Bats shifted frequencies of the first sound in each strobe group upward and the second sound downward by 3-6 kHz. When overlap and ambiguity ceased, frequency shifts ceased also. Frequency differences were small compared with the total broadcast band, which was 75-80 kHz wide, but the harmonic structure of echoes enhances the differences in spectrograms. Bats could use time-frequency comparisons of echoes with broadcasts to assign echoes to the corresponding broadcasts and thus avoid ambiguity.bat sonar | clutter interference | echo delay | FM sounds

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Section: Discussionmentioning

confidence: 91%

mentioning

confidence: 99%

FM echolocating bats shift frequencies to avoid broadcast–echo ambiguity in clutter

Hiryu

Bates²,

Simmons

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

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“…Returning echoes also vary in amplitude as a result of varying distances to objects. Bats compensate for these changes by adapting the amplitude of the successive calls to prevent echo intensities from exceeding an optimal level (38)(39)(40). Additionally, echolocating bats that use frequency-modulated (FM) sonar pulses for echolocation shift their call frequencies upon receiving ambiguous echoes (41).…”

Section: Discussionmentioning

confidence: 99%

Ambient noise induces independent shifts in call frequency and amplitude within the Lombard effect in echolocating bats

Hage

Jiang

Berquist

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

125

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The Lombard effect, an involuntary rise in call amplitude in response to masking ambient noise, represents one of the most efficient mechanisms to optimize signal-to-noise ratio. The Lombard effect occurs in birds and mammals, including humans, and is often associated with several other vocal changes, such as call frequency and duration. Most studies, however, have focused on noisedependent changes in call amplitude. It is therefore still largely unknown how the adaptive changes in call amplitude relate to associated vocal changes such as frequency shifts, how the underlying mechanisms are linked, and if auditory feedback from the changing vocal output is needed. Here, we examined the Lombard effect and the associated changes in call frequency in a highly vocal mammal, echolocating horseshoe bats. We analyzed how bandpassfiltered noise (BFN; bandwidth 20 kHz) affected their echolocation behavior when BFN was centered on different frequencies within their hearing range. Call amplitudes increased only when BFN was centered on the dominant frequency component of the bats' calls. In contrast, call frequencies increased for all but one BFN center frequency tested. Both amplitude and frequency rises were extremely fast and occurred in the first call uttered after noise onset, suggesting that no auditory feedback was required. The different effects that varying the BFN center frequency had on amplitude and frequency rises indicate different neural circuits and/or mechanisms underlying these changes.A ny transmission of signals between sender and receiver faces the challenge of being subjected to masking by noise. For acoustic signals, for example, animals have evolved several strategies that aid in increasing the signal-to-noise ratio, thus facilitating signal transmission. One of the most efficient mechanisms is the socalled Lombard effect, i.e., the involuntary rise in call amplitude in response to masking ambient noise (1). This effect was first described in human communication a century ago (2) and has since been found in several species of birds (3-11) and various mammals (12-17), including bats (18). In human speech, several vocal changes, such as a rise in fundamental frequency (19) or lengthening in word duration (20), are often accompanied with the Lombard effect; combined, these changes are referred to as Lombard speech (21). Vocal changes associated with the Lombard effect have rarely been analyzed in animal species. So far, noisedependent changes in call frequency have been observed in birds (8,11,22), and changes in call duration in birds and monkeys (8,12).Most animal studies, however, have focused on noise-dependent changes in call amplitude and do not examine other possible vocal changes (2-5, 7, 9, 10, 15-17). It is therefore still largely unknown how the adaptive changes in call amplitude relate to frequency shifts or call elongation and how the underlying mechanisms are linked. It is also unknown if auditory feedback from the changing vocal output is needed to drive the Lombard effect in general.Over...

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“…1A), each consisting of a CF component with the second harmonic around 68-70 kHz being strongest, plus an accompanying initial short upward FM sweep (iFM: 2-8 kHz, ending at 68-70 kHz) and a terminal short downward FM sweep (tFM: beginning at 68-70 kHz and extending 8-12 kHz lower) (Hiryu et al, 2008).…”

Section: Subjectsmentioning

confidence: 99%

“…The recording procedure was the same as that used in a previous study (Hiryu et al, 2008). The Telemike consisted of a 1/8-inch omni-directional condenser microphone (Knowles, Model FG-3329, Itasca, Illinois, USA), a miniature custom-designed FM transmitter unit, a 1.5-V hearing-aid battery (Sony, Type SR521SW, Tokyo, Japan), and a transmitting antenna.…”

Section: Telemike Recordingmentioning

confidence: 99%

Investigation of acoustic gaze strategy by Pipistrellus abramus and Rhinolophus ferrumequinum nippon during obstacle avoidance flight

Yamada¹,

Oka²,

Hiryu³

et al. 2013

Proceedings of Meetings on Acoustics

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On-board telemetry of emitted sounds from free-flying bats: compensation for velocity and distance stabilizes echo frequency and amplitude

Cited by 75 publications

References 35 publications

FM echolocating bats shift frequencies to avoid broadcast–echo ambiguity in clutter

FM echolocating bats shift frequencies to avoid broadcast–echo ambiguity in clutter

Ambient noise induces independent shifts in call frequency and amplitude within the Lombard effect in echolocating bats

Investigation of acoustic gaze strategy by Pipistrellus abramus and Rhinolophus ferrumequinum nippon during obstacle avoidance flight

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