Detection and Loudness
• Loudness is the subjective impression
of sound level (and not identical to it!)
Detection and Loudness
• For example,
tones of
different
frequencies
that are judged
to be equally
loud have
different SPLs
(dB)
Detection and Loudness
• Hearing loss due to exposure to high-intensity
sounds (greater than 100 dB) can last many hours
Localization
• recall the lake analogy: task is to
localize the positions of the boats on a
lake using the pattern of ripples at two
points on the shore
Localization
• All you have is a pair of instruments
(basilar membranes) that measure air
pressure fluctuations over time
Localization
• There are several clues you could use:
Localization
Left Ear
Right Ear
Compression
Waves
Localization
•
1
There are several clues you could
use:
arrival time - sound arrives first at ear
closest to source
Localization
Left Ear
Right Ear
Compression
Waves
Localization
•
1.
2.
There are several clues you could
use:
arrival time
phase lag (waves are out of sync) wave at ear farthest from sound
source lags wave at ear nearest to
source
Localization
Left Ear
Right Ear
Compression
Waves
Localization
•
1.
2.
3.
There are several clues you could
use:
arrival time
phase lag (waves are out of sync)
sound shadow (intensity difference)sound is louder at ear closer to sound
source
Localization
•
What are some problems or
limitations?
Localization
•
Low frequency sounds aren’t
attenuated by head shadow
Sound is the same
SPL at both ears
Left Ear
Right Ear
Compression
Waves
Localization
•
Left Ear
Right Ear
High frequency sounds have
ambiguous phase lag
Left Ear
Right Ear
Two locations, same phase information!
Localization
•
These cues only provide azimuth
(left/right) angle, not altitude
(up/down) and not distance
Left Ear
Right Ear
Azimuth
Localization
Additional cues:
Localization
Additional cues:
Head Related Transfer Function:
Pinnae modify the frequency
components differently depending on
sound location
Localization
Additional cues:
Room Echoes:
For each sound, there are 6
“copies” (in a simple
rectanguluar room!).
Different arrival times of
these copies provide cues
to location of sound
relative to the acoustic
space
Localization
• What would be the “worst case”
scenario for localizing a sound?