Flashcards in Audition Deck (18)
What is place theory
-our perception of sound depends on where the frequency (location of maximum displacement) produces vibrations along the basilar membrane
-each position of the basilar membrane is associated with a particular frequency
How is the frequency mapped in the ear according to the place theory?
-the mapping of place is linearly related to frequency with frequency gradually decreasing as one moves from the oval window (base) to the apex of teh cohlea
According to place theory, at the base (oval window) what frequencies does it respond to and what bandwidth does it have?
high and sharp frequencies
small bandwidth - only lets good sounds in
According to place theory, at the apex what frequencies does it respond to and what bandwidth does it have?
low and not sharp frequencies
What is place coding (a concept within place theory)
-pitch discrimination for pure tones should depend on the bandwidth of audio filters
What are the problems with place theory?
-cannot fully account for our ability to discriminate between two tones of similar frequencies
-cant account for the missing fundamental
How do we measure auditory filter bandwidth?
-using masking experiments
-the perception of one sound is affected by the presence of another
what is a critical bandwidth (a concept within place theory)
the smallest band of frequencies around it which will activate the same part of the basilar membrane
what is frequency selectivity
if two sounds of two different frequencies are played together two separate sounds can often be heard rather than a combination tone
what is the missing fundamental
pitch is perceived also by the relationships between harmonics, sometimes the fundamental may not even be present but we can still hear it
What is timing theory
says that our perception of sound depends on the timing patterns to which the neurons respond to sound in cochlea
What is phase-locking (a concept within timing theory?)
the chemical process is timed with how the auditory nerve fires. The principle only works for low frequencies (up to 4 hz) because of the refractory period
What is the volley principle and what does it explain
-it explains how we hear pitches with frequencies higher than 4 Hz
-it explains the perception of pure tones and the missing fundamental
-the summation of different responses for each fibre codes the sound for higher frequencies
Discuss how the timing theory explains the missing fundamental
-the two harmonics of the higher frequencies fit into the same bandwidth (unresolved harmonics)
-the unresolved harmonics produce beats which helps you perceive the missing fundamental called "residue pitch"
What is a problem with the timing theory
-you don't hear the pitch for unresolved harmonics when they say you should
What is pattern theory
-the brain resolves individual sine wave components and analyses frequencies using place code
-it then finds the best firing harmonic series that sound like the fundamental frequency
What can the pattern theory account for?
-the missing fundamental
-for reliance on resolved harmonics