Amplitude discrimination is predictably affected by echo frequency filtering in wideband echolocating bats
Amaro Tuninetti1, Andrea Megela Simmons1, James A Simmons2
1Department of Cognitive, Linguistic, and Psychological Sciences, Brown University, 190 Thayer Street, Providence, Rhode Island 02912, USA.
The Journal of the Acoustical Society of America
|March 2, 2022
Summary
Big brown bats use ultrasonic echolocation for navigation. Experiments show that specific frequency harmonics in their calls are crucial for accurately judging target size and distinguishing it from background noise.
Area of Science:
- Bioacoustics
- Animal Behavior
- Sensory Neuroscience
Background:
- Big brown bats use frequency-modulated (FM) ultrasonic pulses for echolocation.
- Echolocation signals have two main harmonics (FM1 and FM2) affected differently by propagation.
- Previous research linked FM1's low frequencies to target ranging.
Purpose of the Study:
- To investigate how attenuating FM1 or FM2 affects big brown bats' ability to discriminate echo amplitude.
- To test if specific harmonics are essential for distinguishing target echoes from non-target echoes.
Main Methods:
- Bats performed an amplitude discrimination task with virtual targets.
- Echo delay was fixed, amplitude varied, and either FM1 or FM2 was filtered.
- High-pass and low-pass filters selectively attenuated specific frequency ranges.
Main Results:
- Bat performance declined when lower frequencies (FM1) were attenuated in target echoes.
- Performance decreased when higher frequencies (FM2) were attenuated in non-target echoes.
- Reversed filtering conditions produced opposite effects, highlighting harmonic roles.
Conclusions:
- Big brown bats' amplitude discrimination relies on specific frequency components of their echolocation calls.
- Bats demonstrate focused attention to isolate target echoes from background noise based on spectral cues.
Related Concept Videos
01:06Echo
633
The human ear cannot distinguish between two sources of sound if they happen to reach within a specific time interval, typically 0.1 seconds apart. More than this, and they are perceived as separate sources.
Imagine the sound is reflected back to the ears. Assuming that the source is very close to the human, the difference between hearing the two sounds—the emitted sound and the reflected sound—may be more than the minimum time for perceiving distinct sounds. If this is the case,...
Imagine the sound is reflected back to the ears. Assuming that the source is very close to the human, the difference between hearing the two sounds—the emitted sound and the reflected sound—may be more than the minimum time for perceiving distinct sounds. If this is the case,...
633
01:54Convergent Evolution
29.3K
Evolution shapes the features of organisms over time, ensuring that they are suited for the environments in which they live. Sometimes, selection pressure leads to the rise of similar but unrelated adaptations in organisms with no recent common ancestors, a process known as convergent evolution.
29.3K
01:13The Cochlea
46.5K
The cochlea is a coiled structure in the inner ear that contains hair cells—the sensory receptors of the auditory system. Sound waves are transmitted to the cochlea by small bones attached to the eardrum called the ossicles, which vibrate the oval window that leads to the inner ear. This causes fluid in the chambers of the cochlea to move, vibrating the basilar membrane.
46.5K
01:05Doppler Effect - II
3.6K
The Doppler effect has several practical, real-world applications. For instance, meteorologists use Doppler radars to interpret weather events based on the Doppler effect. Typically, a transmitter emits radio waves at a specific frequency toward the sky from a weather station. The radio waves bounce off the clouds and precipitation and travel back to the weather station. The radio frequency of the waves reflected back to the station appears to decrease if the clouds or precipitation are moving...
3.6K
01:01Perception of Sound Waves
4.7K
The human ear is not equally sensitive to all frequencies in the audible range. It may perceive sound waves with the same pressure but different frequencies as having different loudness. Moreover, the perception of sound waves depends on the health of an individual's ears, which decays with age. The health of one's ears may also be affected by regular exposure to loud noises.
The pitch of a sound depends on the frequency and the pressure amplitude of the source. Two sounds of the same...
The pitch of a sound depends on the frequency and the pressure amplitude of the source. Two sounds of the same...
4.7K
01:18Aliasing
270
Accurate signal sampling and reconstruction are crucial in various signal-processing applications. A time-domain signal's spectrum can be revealed using its Fourier transform. When this signal is sampled at a specific frequency, it results in multiple scaled replicas of the original spectrum in the frequency domain. The spacing of these replicas is determined by the sampling frequency.
If the sampling frequency is below the Nyquist rate, these replicas overlap, preventing the original...
If the sampling frequency is below the Nyquist rate, these replicas overlap, preventing the original...
270