Transcript Modeling Auditory Localization of Subwoofer Signals in Multi

Applied Psychoacoustics
Lecture 1: Anatomy and Physiology of the
human auditory system
Jonas Braasch
Overview of the Human Ear
Outer Ear
• Pinna: External cartiledge
– Provides direction dependent frequency cues for
sound localization through spectral filtering
– Position can be actively controlled by some mammals
(e.g., cat)
• Meatus (Auditory Canal)
– Pathway to the middle ear, approx. 7mm diameter,
27mm length
– Amplifies sounds in the range of 2000 to 5000 Hz
through resonance (approx. 10 – 15 dB)
Simulation of the sound pressure
wave in the ear canal
1
3
2
1 frontal, 2.7 kHz
2 lateral, 10 kHz
3 rear, 2.7 kHz
Photo of ear drum
Middle Ear
http://www.bioon.com/book/biology/whole/image/11/11-5.jpg
Middle Ear
Middle Ear
• Tympanic Membrane
– Sound pressure vibration is trancduced into mechanical
oscillation and passed on to the malleus
– protects ear (e.g, water, wind)
• Ossicles
– Malleus, incus, stapes (hammer, anvil, and stirrup)
– are the Smallest bones in human body
• Muscles
– Stapedius muscle (connected to the stapes)
– Tensor tympani muscle (connected to the malleus)
– are the smallest muscles in the human body
• Oval Window
– connection to the cochlea
• Eustachian Tube
– connects the middle ear to the throat for pressure relief
Function of the middle Ear
• Is an impedance transformer
• Without it difference in densities of air and
the cochlear liquid would result in lossy
energy transfer
• Pressure increase the pressure between
the oval window and the ear drum by
nearly a factor of 30
– Amplitude ratio ear (drum/stapes) ~1.3:1
– Area ratio (ear drum /oval window): ~20:1
Acoustic Reflex
• Transmission can be attenuated in the middle
ear by stiffening the Stapedius muscle and the
tensor tympani muscle to protect the inner ear
• Is controlled by the auditory system and react to
loud sound exposure
Arrangement to measure the pressure-force
transfer function of a middle ear (RUB-IKA)
Vibration of the ossicular chain
Vibration of the ossicular chain
Vibration of the ossicular chain
Inner Ear
Semicircular canals
Auditory Nerve
Cochlear
Basilar Membrane
The Traveling Wave in the Basilar Membrane
Frequency Mapping on the BM
Logarithmic Frequency Mapping
http://www.bioon.com/book/biology/whole/image/11/11-10.jpg
Traveling Wave Simulation
250-Hz Tone
1000-Hz Tone
4000-Hz Tone
http://www.boystownhospital.org/Research/Areas/Neurobiological/MoreInfoComLab/traveling_waves.asp
Neurotransmitters
• are chemicals that enable communication
between two neurons
• are released from one neuron at its
presynaptic nerve terminal and cross the
synapse, a small gap, to the receptor of
the second neuron
Connecting the ear to the auditory pathway
•95% of auditory nerve fibres (Type-I fibres: large diameter, myelinated)
innervate IHCs (20- 30 to a single IHC) sending information to the CNS
•5% (Type-II fibres: thin, unmyelinated) innervate OHCs (each fibre
innervating 50-100 OHCs)
Tonotopic organization of auditory
nerve and cochlear nucleus
Definition Tonotopy
(from greek tono- and topos = place: the
place of tones) is the spatial arrangement of
where sound is perceived, transmitted, or
received. It refers to the fact that tones close
to each other in terms of frequency are
represented in topologically neighbouring
neurons in the brain.
from Wikipedia
Cell Response Types
• Primary-like (PL)
• Primary-like, notch (PL-N)
• Phase-lock (onset)
• Onset, lock (O-L)
• Chopper
Cell types
chopper
Primary-like
time
time
Acoustic stimulus
onset
time
Acoustic stimulus
Acoustic stimulus
Primary-like,
notch
time
Acoustic stimulus
Tuning Curves
Post Stimulus Time (PST) Histogram
Phase Locking
action potential
sound pressure
Physiological Coordinate System
Direction
Lateral
Medial
Bilateral
Ipsilateral
Contralateral
Description
Away from the midline
Toward the midline
On both sides of the body or head
On the same side of the body or head
On the opposite side of the body or head