The Ear Flashcards
Sound waves are incident on a human ear.
Describe how the frequency and amplitude of the vibrations change as the wave is transmitted through the ear to the fluid in the inner ear
Frequency does not change
Amplitude is reduced
Sound waves are incident on a human ear
Explain how the components of the ear act to amplify the pressure changes due to the sound wave
Ossicles lever system produces increase in force
Area of oval window much less than area of ear drum
Pressure = F / A so large increase in pressure
State what is meant by the threshold of hearing and state the frequency at which the reference threshold is quoted
Lowest intensity of sound detected by human ear reference intensity (1.0 × 10–12 W m–2) is taken at 1 kHz
Sound intensity levels are usually measured in decibels. Give two reasons why this logarithmic scale is used.
The ear has a logarithmic response
To accommodate a very wide range of sound intensities to which ear can respond
Why was it necessary to introduce an adapted scale referred to as the dBA scale, which is used on some sound level matters?
The dBA scale takes account of the frequency dependence of the sensitivity of the ear
What is the function of the ear drum
Transfers vibration of sound waves into mechanical oscillations the outer ear to the ossciles of the middle ear
What is the function of the ossicles
System of levers to multiply the force (around x 1.5)
What is the function of the windows (oval and round)
Allow sound vibrations to enter the fluid of the inner ear
What is the function of the cochlea
Converts pressure wave in fluid into electrical signal
What are the main differences between the dBA and the dB scales?
dB scale has a flat response with frequency.
dBA scale is frequency compensated.
for dBA, threshold intensities are different for different frequencies
What is the main difference between age related hearing loss and noise-induced hearing loss?
loss due to age increases with frequency
loss due to noise is maximum at 4000 Hz
State the frequency of sound at which the normal ear is most sensitive
3 kHz
State the main features of hearing loss in terms of frequency response for
age-related hearing loss
as f increases, loss increases
State the main features of hearing loss in terms of frequency response for
noise-related hearing loss
loss is maximum at 4 kHz
Define intensity
power per unit cross-sectional area (in path of wave)
State what is meant by attenuation and what causes it.
reduction in intensity/energy/power as wave travels through a medium due to absorption/scattering/diffraction
Define the threshold of hearing, Io
Minimum intensity heard by normal / average ear
At frequency of 1kHz
Describe how the vibrations of a sound wave are received by the outer ear and transmitted to the inner ear.
longitudinal/pressure waves in the ear canal
forces eardrum into mechanical vibrations.
(Mechanical) vibrations (passed through middle ear) by a lever
system/series of bones/named bones to the oval window
sets up pressure waves in fluid in cochlea
Explain how the pressure changes due to the sound wave are amplified by the ear.
force increased by the action of the lever system/series of
bones/named bones; value F × 1.5
area of oval window «_space;area of the eardrum ; value A/20
effect of pinna in increasing intensity in ear canal
intensity is proportional to
amplitude squared
The ear acts as a
Transducer, converting sound energy into electrical energy
Where does the db and dba scale meet?
1000 Hz
Draw a graph of intensity against frequency (log)
Intensity scale (10^-2) to 10^2, at 1 is the threshold of feeling The curve starts at 20 and ends at 20000, with the minimum point at 3000 hz
Increase in loudness is proportional to
log(new intensity/original intensity)
