pulse echo measurements Flashcards
animals that use echolocation
bats and dolphins
frequency of bats chirp
50-1000kHz, lasting 3 milliseconds
how does echolocation help bats see
sensitive ears, brain measures time delay + calculate distance = speed x time
how do dolphins differ from bats
dolphins can build a mental image of what’s around them
speed of sound in air
330ms-1
human uses for pulse echo measurements
sonar, medical imaging, air traffic control, distance of asteroids and the moon
when do humans use pulse echo measurements
when other methods are difficult / dangerous
low frequency sounds travel
further than high frequency sounds
calling at high frequency (more often) gives bats
clearer images - more detailed more precise location as they get closer
as frequency of chirps increases
wavelength decreases
when wavelength decreases
resolution increases as more detail as it refracts less
intensity of a progressive wave
the gradient power passing through a surface per unit area
bats echolocation can be reflected off an objected up to
5m away - any further and echo is too attenuated
I=P/A
I=P/4PIR2
inverse square rule
intensity is inversely proportional to the square of the distance
if distance doubles
intensity decreases by quadruple
decreased amplitude
particles oscillate less
intensity is proportional to
amplitude squared
birds detect
reflection of clicks
the closer the object
the shorter the time for the click to return
half the wavelength
should be less than the distance
if incoming and outgoing pulses overlap
info is lost
longer wait time
less collection
minimum distance of detection =
distance wave can travel during pulse
max distance of detection
distance wave can travel in time between pulses
if obstacle closer than half a wavelength
sounds may detract - can’t detect
min time of travel must equal
pulse direction to avoid overlap
