Transcript 2320Lecture7

Reading Assignment!
We’ll discuss the chapter by Gregory
in your book on Friday of next week
Hearing:
Detection
Loudness
Localization
Music
Speech
Detection and Loudness
• Sound level is measured in decibels (dB)
- a measure of the amplitude of air
pressure fluctuations
Detection and Loudness
• Sound level is measured in decibels (dB)
- a measure of the amplitude of air
pressure fluctuations
• dB is a log scale - 1 dB difference = 10
times the actual air pressure
Detection and Loudness
• Sound level is measured in decibels (dB)
- a measure of the amplitude of air
pressure fluctuations
• dB is a log scale - 1 dB difference = 10
times the actual air pressure
• We have a dynamic range that is a factor
of 7.5 million!
Detection and Loudness
• minimum sound level necessary to be heard
is the detection threshold
Detection and Loudness
• detection threshold depends on frequency
of sound:
• very high and very low frequencies must have
more energy (higher dB) to be heard
• greatest sensitivity (lowest detection threshold) is
between 1000 hz to 5000hz
Detection and Loudness
• Detection can be compromised by a
masking sound
• even masking sounds that are not
simultaneous with the target can cause
masking (forward and backward
masking)
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
•
There are several clues you could use:
1
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
•
There are several clues you could use:
1.
2.
3.
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?