STUDY QUESTIONS AUDITORY SYSTEM
What distinguishes a sound, a sound and a noise?
Sound: pure sine wave with always the same period, not actually found in nature
Sound: mixing several tones, the fundamental sine curve is superimposed by other tones
with a frequency equal to an integer multiple of the fundamental frequency
Noise: many different frequencies and amplitudes mixed unsystematically and without
pattern
In which frequency range does the human auditory system work?
approx. 20 Hz to 16000 Hz
Is a certain sound pressure perceived as equally loud at all audible frequencies?
No
You buy a pair of earplugs with 40 dB (A) attenuation. What does that mean?
That the earplugs cause a hundredfold attenuation of auditory signals.
How is the middle ear structured? What is its function?
The middle ear consists of the three ossicles (hammer, anvil and stirrup) and is laterally
separated from the outer auditory canal by the eardrum and from the inner ear by the oval
window. When sound from the ear canal causes the eardrum to vibrate, it is first transmitted
to the ossicles and then to the oval window and thus the cochlea. The auditory ossicles
mainly have a lever function, on the one hand to compensate for the different impedance
between the air in the middle ear and the fluid in the inner ear, on the other hand to amplify
the incoming signal. Due to the leverage effect of the middle ear bones in combination with
the transmission of the vibrations to smaller and smaller surfaces, this results in an
approximately 44-fold pressure amplification of the original signal.
How is middle ear hearing loss different from inner ear hearing loss?
In a middle ear hearing loss, the cause of the hearing loss lies in the middle ear, for example,
if the middle ear bones are not functional. The sound cannot be transmitted from the external
auditory canal to the inner ear. This is also referred to as conductive hearing loss.
In inner ear hearing loss, the cause of hearing loss lies in the inner ear, for example when
hair cells are damaged or missing from birth. The sound is transmitted to the cochlea, but no
mechano-electrical transformation takes place. This is also referred to as sensorineural
hearing loss.
Explain the structure of the cochlea.
The cochlea is a fluid-filled structure that adjoins the middle ear and ossicles through the oval
window. It consists of two fluid-filled ducts (scala vestibuli and scala tympani) connected at
the tip of the cochlea. At the end of the second aisle is the round window. Between the two
fluid ducts sits the Corti organ, which consists of the basilar membrane with hair cells and the
tectorial membrane. The hair cells can be divided into about 4500 inner, predominantly
afferent and about 12000 external, predominantly efferent hair cells, whereby the inner hair
cells represent the actual sensory receptors.
Which sensory cells perform the mechanoelectric transformation in the auditory
system?
The inner hair cells.
What distinguishes a sound, a sound and a noise?
Sound: pure sine wave with always the same period, not actually found in nature
Sound: mixing several tones, the fundamental sine curve is superimposed by other tones
with a frequency equal to an integer multiple of the fundamental frequency
Noise: many different frequencies and amplitudes mixed unsystematically and without
pattern
In which frequency range does the human auditory system work?
approx. 20 Hz to 16000 Hz
Is a certain sound pressure perceived as equally loud at all audible frequencies?
No
You buy a pair of earplugs with 40 dB (A) attenuation. What does that mean?
That the earplugs cause a hundredfold attenuation of auditory signals.
How is the middle ear structured? What is its function?
The middle ear consists of the three ossicles (hammer, anvil and stirrup) and is laterally
separated from the outer auditory canal by the eardrum and from the inner ear by the oval
window. When sound from the ear canal causes the eardrum to vibrate, it is first transmitted
to the ossicles and then to the oval window and thus the cochlea. The auditory ossicles
mainly have a lever function, on the one hand to compensate for the different impedance
between the air in the middle ear and the fluid in the inner ear, on the other hand to amplify
the incoming signal. Due to the leverage effect of the middle ear bones in combination with
the transmission of the vibrations to smaller and smaller surfaces, this results in an
approximately 44-fold pressure amplification of the original signal.
How is middle ear hearing loss different from inner ear hearing loss?
In a middle ear hearing loss, the cause of the hearing loss lies in the middle ear, for example,
if the middle ear bones are not functional. The sound cannot be transmitted from the external
auditory canal to the inner ear. This is also referred to as conductive hearing loss.
In inner ear hearing loss, the cause of hearing loss lies in the inner ear, for example when
hair cells are damaged or missing from birth. The sound is transmitted to the cochlea, but no
mechano-electrical transformation takes place. This is also referred to as sensorineural
hearing loss.
Explain the structure of the cochlea.
The cochlea is a fluid-filled structure that adjoins the middle ear and ossicles through the oval
window. It consists of two fluid-filled ducts (scala vestibuli and scala tympani) connected at
the tip of the cochlea. At the end of the second aisle is the round window. Between the two
fluid ducts sits the Corti organ, which consists of the basilar membrane with hair cells and the
tectorial membrane. The hair cells can be divided into about 4500 inner, predominantly
afferent and about 12000 external, predominantly efferent hair cells, whereby the inner hair
cells represent the actual sensory receptors.
Which sensory cells perform the mechanoelectric transformation in the auditory
system?
The inner hair cells.
