Auditory Dimensions of Acoustic Images in Echolocation

Simmons, James A.; Ferragamo, Michael J.; Saillant, Prestor A.; Haresign, Tim; Wotton, Janine M.; Dear, Steven P.; Lee, David N.

doi:10.1007/978-1-4612-2556-0_4

Cited by 51 publications

(68 citation statements)

References 55 publications

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“…Carollia produces broadband and high-frequency FM signals which are well suited for this task. Hence, Carollia could potentially use dierences in surface texture as a cue to distinguish ripe from unripe fruits and fruits from other objects by analyzing dierences in the spectral or temporal signature of the returning echo (Bradbury 1970;Habersetzer and Vogler 1983;Mogdans and Schnitzler 1990;Ostwald et al 1988;Schmidt 1988;Simmons and Vernon 1971;Simmons et al 1974Simmons et al , 1995. However, our study with untrained bats in the¯ight cage showed that both species approached, and even bit into foam rubber models of Piper which clearly diered in surface structure from real fruits.…”

Section: Role Of Surface Structurementioning

confidence: 73%

“…Since leaf-nosed bats echolocate (e.g., Barclay et al 1981;Belwood 1988;Howell 1974) and produce short, multiharmonic, downward frequency-modulated (FM) signals of low sound pressure level (SPL), they could possibly use echolocation to perform those tasks. Short, broadband FM signals are well suited for exact localization and spectral characterization of targets (e.g., Schnitzler and Henson 1980;Simmons et al 1995). However, because these bats glean mostly stationary food from vegetation or the ground (e.g., insects or fruits), the returning echoes of the food are often buried in a multitude of clutter-echoes from leaves, branches, and surfaces on which the food rests (highly cluttered space).…”

Section: Introductionmentioning

confidence: 99%

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The roles of echolocation and olfaction in two Neotropical fruit-eating bats, Carollia perspicillata and C. castanea , feeding on Piper

Thies

Kalko

Schnitzler

1998

Behavioral Ecology and Sociobiology

207

224

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We studied the echolocation and foraging behavior of two Neotropical frugivorous leaf-nosed bats (Carollia perspicillata, C. castanea: Phyllostomidae) in ā ight cage. To test which cues Carollia uses to detect, identify, and localize ripe Piper fruit, their preferred natural food, we conducted experiments under seminatural conditions with ripe, unripe, and arti®cal fruits. We ®rst oered the bats ripe fruits and documented their foraging behavior using multi¯ash stereophotography combined with simultaneous sound recordings. Both species showed a similar, stereotyped foraging pattern. In search¯ight, the bats circled through the¯ight cage in search of a branch with ripe fruit. After ®nding such a branch, the bats switched to approach behavior, consisting of multiple exploration¯ights and the ®nal approach when the bats picked up the fruit at its tip and tore it o in¯ight. Our behavioral experiments revealed that odor plays an important role in enabling Carollia to ®nd ripe fruit. While foraging, Carollia always echolocated and produced multiharmonic, frequency-modulated (FM) signals of broad bandwidth, high frequency, short duration, and low intensity. We discriminated an orientation phase (mostly a single pulse per wingbeat) and an approach phase (groups of two to six pulses per wing beat). We conclude from the bats' behavioral reaction to real and arti®cial fruit as well as from characteristic patterns in their echolocation behavior that during exploration¯ights, Carollia changes from primarily odor-oriented detection and initial localization of ripe fruit to a primarily echo-oriented ®nal localization of the position of the fruit.

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Section: Role Of Surface Structurementioning

confidence: 73%

Section: Introductionmentioning

confidence: 99%

The roles of echolocation and olfaction in two Neotropical fruit-eating bats, Carollia perspicillata and C. castanea , feeding on Piper

Thies

Kalko

Schnitzler

1998

Behavioral Ecology and Sociobiology

207

224

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“…The value of Q is a well known quantity that represents the sharpness (''quality'') of the filtering imposed on echoes independent of frequency, but it also is the relative width of the target impulse response in number of cycles or peaks (16). From previous experimental results, big brown bats appear to perceive the shape of targets in terms of the distribution of reflecting points along the range axis (3,8), which is equivalent to the distribution of peaks in the target's impulse response. By expressing the bandwidth of echoes normalized to frequency, and thus the time-extent of the impulse response in normalized, or dimensionless, time, the bat may display shape as the number of parts in the target independent of their actual time separations.…”

mentioning

confidence: 93%

“…Big brown bats, Eptesicus fuscus (4), broadcast wideband, multipleharmonic, downward-sweeping, frequency-modulated (FM) biosonar sounds covering frequencies from 22 to 100 kHz (3,5,6), and they perceive objects from echoes of these sounds that return to their ears. Bats determine target distance, or range, from the delay of echoes, which is 5.8 ms͞m (7)(8)(9). In principle, the high center frequency (f c ϭ Ϸ60 kHz) and wide bandwidth (⌬f ϭ Ϸ80 kHz) of the big brown bat's FM signals can support very accurate determination of delay (10,11).…”

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confidence: 99%

“…By expressing the bandwidth of echoes normalized to frequency, and thus the time-extent of the impulse response in normalized, or dimensionless, time, the bat may display shape as the number of parts in the target independent of their actual time separations. This efficient abstract representation may be responsible for the demonstrated abilities of echolocating bats to classify rapidly moving targets in multipleobject ''scenes'' (3,8).…”

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confidence: 99%

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Delay accuracy in bat sonar is related to the reciprocal of normalized echo bandwidth, or Q

Simmons

Neretti

Intrator

et al. 2004

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

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Big brown bats (Eptesicus fuscus) emit wideband, frequencymodulated biosonar sounds and perceive the distance to objects from the delay of echoes. Bats remember delays and patterns of delay from one broadcast to the next, and they may rely on delays to perceive target scenes. While emitting a series of broadcasts, they can detect very small changes in delay based on their estimates of delay for successive echoes, which are derived from an auditory time͞frequency representation of frequency-modulated sounds. To understand how bats perceive objects, we need to know how information distributed across the time͞frequency surface is brought together to estimate delay. To assess this transformation, we measured how alteration of the frequency content of echoes affects the sharpness of the bat's delay estimates from the distribution of errors in a psychophysical task for detecting changes in delay. For unrestricted echo frequency content and high echo signal-to-noise ratio, bats can detect extremely small changes in delay of about 10 ns. When echo bandwidth is restricted by filtering out low or high frequencies, the bat's delay acuity declines in relation to the reciprocal of relative echo bandwidth, expressed as Q, which also is the relative width of the target impulse response in cycles rather than time. This normalized-time dimension may be efficient for target classification if it leads to target shape being displayed independent of size. This relation may originate from cochlear transduction by parallel frequency channels with active amplification, which creates the auditory time͞frequency representation itself.

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Perspectives and Progress in Animal Acoustic Communication

Simmons¹

Acoustic Communication

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Auditory Dimensions of Acoustic Images in Echolocation

Cited by 51 publications

References 55 publications

The roles of echolocation and olfaction in two Neotropical fruit-eating bats, Carollia perspicillata and C. castanea , feeding on Piper

The roles of echolocation and olfaction in two Neotropical fruit-eating bats, Carollia perspicillata and C. castanea , feeding on Piper

Delay accuracy in bat sonar is related to the reciprocal of normalized echo bandwidth, or Q

Perspectives and Progress in Animal Acoustic Communication

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