Echolocation Flashcards
Echolocation
• Use echoes of sounds produced to locate objects
Who does echolocation?
– Chiroptera – navigation & hunting – Odontoceti – navigation & hunting? – Soricomorpha – navigation – Afrosoricida – navigation – Rodentia – navigation
• Water is much denser than air
– Sound travels 4X faster in water
– Sound attenuates more rapidly in air
• Aquatic echolocating mammal
– Signals transmitted farther and return faster
– Less energy used for signal of given intensity
Echolocation calls can be described in terms of
time, frequency, and intensity
Echolocation in bats
• Brief pulses of sound •Frequency varies widely among species • Intensity (decibels) • Bandwidth (breadth of frequencies produced)
Range Limits
• Echolocation is a short-range system in air
– Targets detected at close range
– Requires slower, more maneuverable flight
High-Frequency Sound
• Rapidly attenuated in air
• Why use high frequencies?
– High frequency = short wavelength
– Objects equal in size to wavelength reflect that wavelength well
– Low frequency sounds have long wavelengths
• Tend to bend around small objects instead of being reflected
How do bats distinguish incoming from
outgoing calls?
- Duty cycles (high or low)
2. Self deafening
• Clicks
– Produced in nasal passages in odontocetes
– Produced with tongue in two genera of pteropodids
• Vocal signals
– Produced in larynx in most echolocating
chiropterans and soricomorphs
– Low duty cycle approach
- Produce signals small percentage of time
* Do not broadcast and receive signals simultaneously
– High duty cycle approach
• Produce signals larger percentage of time
• Produce pulses and receive echoes simultaneously
• Doppler-shifted echoes
-Distinguish echo by frequency
Self-Deafening
• Middle and inner ear are insulated from the rest of
the skull
• Two ear muscles dampen sounds – Tensor tympani • Changes tension in tympanic membrane – Stapedius • Changes contact between stapes and oval window
