Animal Communication Exam 1 – Animal Behavior Study Guide, Key Concepts
and Practice Questions
Oilbirds produce clicks in damp caves and use the echoes to orient and avoid obstacles. If an
oilbird has the same auditory sensitivity as a human, i.e. can hear sound above 0 dB, how far
could it detect an obstacle if the clicks register 78 dB 1 m from the bird? - ✔✔6dB for every
doubling of distance → is this a constant????
● 78/6=13
● 2^13=number we multiply our initial distance by to find total distance
● Final answer = 1*2^13=8192m (multiply by one b/c that's initial distance)...and divide this
number in half!!! (See comment below)
● I asked him about this question, and he said to keep in mind that the sound goes toward the
object and echoes back. So this length should be halved. He also said in reality, it stops at 30 dB
rather than all the way at 0 dB, which would decrease the length significantly
Will the Fourier analysis of a mixture of two tones, 1 kHz and 5 kHz, emitted for either 1 second
or 1/100 of a second be different? How and why? - ✔✔The fourier analysis would have the
same waveform because the frequencies do not change based off the amount of time. However,
the number of sidebands would be less for the 1/100 of a second analysis
Explain why it is impossible to measure frequency and duration with certainty at the same time
using Fourier analysis (or our ears) - ✔✔Uncertainty principle - any fourier analyzer needs
several cycles of a signal to compute component frequencies. The more cycles of a stable
frequency that an analyzer can measure, the more accurate the measurement of the frequency.
If the analyzer only has a short time to estimate frequencies, each component will appear as a
wide band in the frequency spectrum. If a longer duration is available, frequencies components
will be narrower. The uncertainty principle limits the precision of simultaneous measurement of
duration and sound.
Give the three main sources of distortion for frequency modulated signals. Which is likely to
have the largest effect in air? - ✔✔Spherical spreading??
● Heat loss (will not distort- Dr. Wilkinson)
,○ the amplitude of sound decreases with distance as heat increase
○ Heat losses increase with square of sound frequency, so higher frequency sounds decrease in
amplitude more with heat than lower frequency sounds
○ Medium also plays a role: heat loss for seawater>freshwater, air>seawater, solid
substrates>air
○ [See page 72 from textbook]
● Scattering ○ Occurs when sound from sender encounters objects with different acoustic
impedances from the medium. Filters out higher frequency components.
○ [See page 72 from textbook]
● Boundary effects
○ Occur when a sound encounters a boundary with a different acoustic impedance than the
medium the sound was sent in
■ Case 1: boundary is near medium results in a direct and reflected wave (can result in positive
or negative interference)
■ Case 2: sound propagates between two parallel boundaries (such as in cave, walls of cave vs
ground)
■ Case 3: both sender and receiver live in a medium but communicate across a boundary that's
a different medium (such as insects that communicate with other insects by vibrating a plant)
○ [pages 73-78]
● LARGEST EFFECT IN AIR??
○ Probably heat loss: "In air, heat losses are more variable than in water, as they are sensitive to
fluctuating temperature and humidity." (page 72)
○ Boundary effects and scattering can happen in a variety of media
Use graphs to predict the optimal frequency of sound to use for long distance communication.
Show and explain how the optimal frequency should differ for animals calling from the ground
vs calling from the air - ✔✔idk yet
Describe a situation in air and in water that would create a sound shadow and a sound channel
(give four different situations) - ✔✔Sound shadow in air- sound traveling parallel to the ground
, on a hot day will be refracted upwrd because the warm ground heats the immediately adjacent
layer of air, generating a gradient of decreasing air temperatures with increasing height above
the ground. At a sufficient distance from the sender, a sound shadow is created.
Sound shadow in water- in temperate summer, sound traveling parallel to the surface of the
water will refract downward creating a sound shadow a distance away from the sender near the
surface of the water
Sound channel in air - At dawn or on a clear night, the earth radiates heat back into the sky so
there is a temperature gradient of increasing temperatures with increasing height above the
ground. Sound travelling parallel to the ground from the sender to the receiver is initially
refracted downward at the ground then reflected back up towards the receiver. Sound initially
travelling above the receiver is refracted down towards the receiver. This creates a sound
channel. (Can also use forest example: colder under canapy of trees, creating channel.)
Sound channel in water - During cold winter, the surface of the water is colder than at mid
depths. Sound travelling parallel to the surface refracts upward then reflects off the surface
back downward towards receiver. Sound travelling initially downward gets refracted upward
towards the receiver. This creates a sound channel
Many animals emit contact cells to coordinate group movements. For these calls to be effective
at communicating the range of an animal, what characteristics must they possess? How would
you expect these features to differ in the animal was a dolphin versus a vervet monkey? -
✔✔They must have the appropriate bandwith, frequency, duration, modulation type and rate,
location of sender and receiver, and transmission medium.
Dolphins - sound propagates in water better than air, less attenuation of high frequency sounds
Vervet monkeys - lower frequency sounds so they are able to propagate far enough.
Why does a pressure differential detector ear provide more directional information than a
pressure detector ear? - ✔✔Particle detectors can measure directionality, so I'm assuming the
pressure differential detector has these unlike the pressure detector ear
Parallel to tube, perpendicular to membrane; pressure intensity tells you the directionality
Way pressure waves travel, way membrane is hit
and Practice Questions
Oilbirds produce clicks in damp caves and use the echoes to orient and avoid obstacles. If an
oilbird has the same auditory sensitivity as a human, i.e. can hear sound above 0 dB, how far
could it detect an obstacle if the clicks register 78 dB 1 m from the bird? - ✔✔6dB for every
doubling of distance → is this a constant????
● 78/6=13
● 2^13=number we multiply our initial distance by to find total distance
● Final answer = 1*2^13=8192m (multiply by one b/c that's initial distance)...and divide this
number in half!!! (See comment below)
● I asked him about this question, and he said to keep in mind that the sound goes toward the
object and echoes back. So this length should be halved. He also said in reality, it stops at 30 dB
rather than all the way at 0 dB, which would decrease the length significantly
Will the Fourier analysis of a mixture of two tones, 1 kHz and 5 kHz, emitted for either 1 second
or 1/100 of a second be different? How and why? - ✔✔The fourier analysis would have the
same waveform because the frequencies do not change based off the amount of time. However,
the number of sidebands would be less for the 1/100 of a second analysis
Explain why it is impossible to measure frequency and duration with certainty at the same time
using Fourier analysis (or our ears) - ✔✔Uncertainty principle - any fourier analyzer needs
several cycles of a signal to compute component frequencies. The more cycles of a stable
frequency that an analyzer can measure, the more accurate the measurement of the frequency.
If the analyzer only has a short time to estimate frequencies, each component will appear as a
wide band in the frequency spectrum. If a longer duration is available, frequencies components
will be narrower. The uncertainty principle limits the precision of simultaneous measurement of
duration and sound.
Give the three main sources of distortion for frequency modulated signals. Which is likely to
have the largest effect in air? - ✔✔Spherical spreading??
● Heat loss (will not distort- Dr. Wilkinson)
,○ the amplitude of sound decreases with distance as heat increase
○ Heat losses increase with square of sound frequency, so higher frequency sounds decrease in
amplitude more with heat than lower frequency sounds
○ Medium also plays a role: heat loss for seawater>freshwater, air>seawater, solid
substrates>air
○ [See page 72 from textbook]
● Scattering ○ Occurs when sound from sender encounters objects with different acoustic
impedances from the medium. Filters out higher frequency components.
○ [See page 72 from textbook]
● Boundary effects
○ Occur when a sound encounters a boundary with a different acoustic impedance than the
medium the sound was sent in
■ Case 1: boundary is near medium results in a direct and reflected wave (can result in positive
or negative interference)
■ Case 2: sound propagates between two parallel boundaries (such as in cave, walls of cave vs
ground)
■ Case 3: both sender and receiver live in a medium but communicate across a boundary that's
a different medium (such as insects that communicate with other insects by vibrating a plant)
○ [pages 73-78]
● LARGEST EFFECT IN AIR??
○ Probably heat loss: "In air, heat losses are more variable than in water, as they are sensitive to
fluctuating temperature and humidity." (page 72)
○ Boundary effects and scattering can happen in a variety of media
Use graphs to predict the optimal frequency of sound to use for long distance communication.
Show and explain how the optimal frequency should differ for animals calling from the ground
vs calling from the air - ✔✔idk yet
Describe a situation in air and in water that would create a sound shadow and a sound channel
(give four different situations) - ✔✔Sound shadow in air- sound traveling parallel to the ground
, on a hot day will be refracted upwrd because the warm ground heats the immediately adjacent
layer of air, generating a gradient of decreasing air temperatures with increasing height above
the ground. At a sufficient distance from the sender, a sound shadow is created.
Sound shadow in water- in temperate summer, sound traveling parallel to the surface of the
water will refract downward creating a sound shadow a distance away from the sender near the
surface of the water
Sound channel in air - At dawn or on a clear night, the earth radiates heat back into the sky so
there is a temperature gradient of increasing temperatures with increasing height above the
ground. Sound travelling parallel to the ground from the sender to the receiver is initially
refracted downward at the ground then reflected back up towards the receiver. Sound initially
travelling above the receiver is refracted down towards the receiver. This creates a sound
channel. (Can also use forest example: colder under canapy of trees, creating channel.)
Sound channel in water - During cold winter, the surface of the water is colder than at mid
depths. Sound travelling parallel to the surface refracts upward then reflects off the surface
back downward towards receiver. Sound travelling initially downward gets refracted upward
towards the receiver. This creates a sound channel
Many animals emit contact cells to coordinate group movements. For these calls to be effective
at communicating the range of an animal, what characteristics must they possess? How would
you expect these features to differ in the animal was a dolphin versus a vervet monkey? -
✔✔They must have the appropriate bandwith, frequency, duration, modulation type and rate,
location of sender and receiver, and transmission medium.
Dolphins - sound propagates in water better than air, less attenuation of high frequency sounds
Vervet monkeys - lower frequency sounds so they are able to propagate far enough.
Why does a pressure differential detector ear provide more directional information than a
pressure detector ear? - ✔✔Particle detectors can measure directionality, so I'm assuming the
pressure differential detector has these unlike the pressure detector ear
Parallel to tube, perpendicular to membrane; pressure intensity tells you the directionality
Way pressure waves travel, way membrane is hit
