Biomedical Instrumentation Questions and Answers – Mechanism of Hearing

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This set of Biomedical Instrumentation Multiple Choice Questions & Answers (MCQs) focuses on “Mechanism of Hearing”.

1. The tympanic membrane separates the ear canal from the _____________
a) upper ear cavity
b) lower ear cavity
c) middle ear cavity
d) inner ear cavity
View Answer

Answer: c
Explanation: The tympanic membrane separates the ear canal from the middle ear cavity. The pinna scatters acoustic waves so that some of the scattered energy enters the auditory canal and pushes against the tympanic membrane during a wave of compression. The distance membrane moves is a function of the force and velocity with which the air molecules strike it and is, therefore, related to the loudness of sound.
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2. The middle ear is exposed to atmospheric pressure only through the _______
a) eustachian tube
b) tympanic membrane
c) pinna
d) auditory nerve
View Answer

Answer: a
Explanation: The middle ear is exposed to atmospheric pressure only through the eustachian tube, which connects it to the pharynx and nose or mouth. The sound energy from the tympanic membrane is transmitted through the cavity of the middle ear, to the receptor cells in the inner ear, which are surrounded by fluid. The tympanic membrane separates the ear canal from the middle ear cavity.

3. The major function of the middle ear is ____________
a) to transfer movements of the air in the outer ear to the cochlea
b) to transfer movements of the air in the outer ear to the auditory nerves
c) to transfer movements of the air in the outer ear to the tympanic membrane
d) to transfer movements of the air in the outer ear to the fluid-filled chambers of the inner ear
View Answer

Answer: d
Explanation: Thus, the major function of the middle ear is to transfer movements of the air in the outer ear to the fluid-filled chambers of the inner ear. A chain of three small, middle ear bones couple the tympanic membrane to a membrane covered opening, called the oval window. The total force on the oval window is the same as that on the tympanic membrane.
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4. The human ear responses to vibrations ranging from ___________
a) 20KHz – 20MHz
b) 2KHz – 20MHz
c) 20Hz – 20KHz
d) 2Hz – 2KHz
View Answer

Answer: c
Explanation: The human ear responds to vibrations ranging from 20 to 20,000 Hz. The waves of speech and many other common sounds are not of single frequency but are complex waves made up of several frequencies of vibration. The number of sound frequencies in addition to the fundamental tone, i.e. the degree of purity of the sound wave is related to the quality or timbre of the sound. The human ear can in fact, distinguish some 400,000 different sounds.

5. Name the bone that rests upon the lower end of the cochlea and passes the vibrations directly into the fluid within.
a) malleus
b) stapes
c) incus
d) hammer
View Answer

Answer: b
Explanation: One of the bones, called the stapes, rests upon the lower end of the cochlea and passes the vibrations directly into the fluid within. A chain of three small, middle ear bones couple the tympanic membrane to a membrane covered opening, called the oval window. The total force on the oval window is the same as that on the tympanic membrane.
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6. Air conduction, by definition, is the transmission of sound through the external and middle ear to the internal ear.
a) True
b) False
View Answer

Answer: a
Explanation: It is true. Air conduction, by definition, is the transmission of sound through the external and middle ear to the internal ear. Bone conduction, on the other hand, refers to the transmission of sound to the internal ear mediated by mechanical vibration of the cranial bones and soft tissues. Clinical observation has shown that hard-of-hearing patients with middle ear disease usually have normal hearing by bone conduction, whereas patients with inner ear involvement have decreased or diminished bone-conduction.

7. The hearing threshold is an invariable fixed intensity above which sound is always heard and below which sound is never heard.
a) True
b) False
View Answer

Answer: a
Explanation: It is False. The hearing threshold is not an invariable fixed intensity above which sound is always heard and below which sound is never heard. In fact, the sensitivity of the auditory mechanism is found to vary with interactions between certain physiological, psychological and physical factors. Therefore, the threshold may be regarded as an intensity range within which sound stimuli at or near the statistically determined threshold may or may not be perceived.
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8. Unit of sound intensity ________
a) joules per sq. cm
b) watt per sq. cm
c) joules per cm
d) watt per cm
View Answer

Answer: b
Explanation: Sound intensity may be defined as the amount of energy flow per unit time through a unit area perpendicular to the direction of energy flow. It is expressed as watts per square centimetre. However, the common receivers of sound are microphones, which do not measure sound intensity directly.

9. Sound intensity is proportional to the _________ of sound pressure.
a) cube
b) square
c) inverse square
d) inverse square root
View Answer

Answer: b
Explanation: Sound intensity is proportional to the square of sound pressure. Sound pressure, for a given sinusoidal event, is related linearly to both amplitude and frequency. Sound intensity may be defined as the amount of energy flow per unit time through a unit area perpendicular to the direction of energy flow.
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10. Decibel expresses the logarithm of the ratio between two sound _________
a) intensities
b) powers
c) pressures
d) intensities, powers and pressures
View Answer

Answer: d
Explanation: Decibel expresses the logarithm of the ratio between two sound intensities, powers or sound pressures. The convenient unit for making such comparisons and to express the sound intensity and sound pressure data for all practical purposes is the decibel (dB). The dB is 1/10 of a larger unit, the bell, named after Alexander Graham Bell.

11. What is the unit of dB?
a) watts per sq cm
b) dyne per sq cm
c) unit less
d) watts per cm
View Answer

Answer: c
Explanation: Since dB is merely a ratio, it is a dimensionless entity. Decibel expresses the logarithm of the ratio between two sound intensities, powers or sound pressures. Use of decibels as units for comparison of intensities help to avoid all mathematical calculations except algebraic addition or subtraction of small numbers. The transmission efficiency of any medium like air, a hearing aid or an amplifier is usually expressed in dB as a gain when the output is greater and as a loss, if less.

12. If I1 and I2 are two intensities in watts per square centimetre, then the number of decibels with which they are related can be expressed as _________
a) N = 10 log I1/I2
b) N = 10 log I2/I1
c) N = -10 log I1/I2
d) N = log I1/I2
View Answer

Answer: a
Explanation: If I1 and I2 are two intensities in watts per square centimetre, then the number of decibels with which they are related can be expressed as N = 10 log I1/I2. Attenuation is commonly expressed in negative dB numbers whereas amplification is given in positive dB numbers. Use of decibels as units for comparison of intensities help to avoid all mathematical calculations except algebraic addition or subtraction of small numbers. The transmission efficiency of any medium like air, a hearing aid or an amplifier is usually expressed in dB as a gain when the output is greater and as a loss, if less.

13. __________ is specialized equipment, which is used for the identification of hearing the loss in individuals.
a) gaugemeter
b) tachometer
c) manometer
d) audiometer
View Answer

Answer: d
Explanation: An audiometer is specialized equipment, which is used for the identification of hearing the loss in individuals, and the quantitative determination of the degree and nature of such a loss. Both frequency and output are adjustable over the audio range. The instrument is also provided with a calibrated noise source and bone-conductor vibrator. It is essentially an oscillator driving a pair of headphones and is calibrated in terms of frequency and acoustic output.

14. Which threshold of hearing is measured by a pure-tone audiometer?
a) air-conduction thresholds of hearing
b) bone-conduction thresholds of hearing
c) speech reception thresholds for diagnostic purposes
d) air-conduction and bone-conduction thresholds of hearing
View Answer

Answer: d
Explanation: A pure-tone audiometer is used primarily to obtain air-conduction and bone-conduction thresholds of hearing. Audiometers may be divided into two main groups on the basis of the type of stimulus they provide to elicit an auditory response: pure-tone audiometers and speech audiometers. These thresholds are helpful in the diagnosis of hearing loss.

15. Speech audiometers are normally used to determine ______________
a) speech reception thresholds for diagnostic purposes
b) air-conduction and bone-conduction thresholds of hearing
c) bone-conduction thresholds of hearing
d) air-conduction thresholds of hearing
View Answer

Answer: a
Explanation: Speech audiometers are normally used to determine speech reception thresholds for diagnostic purposes and to assess and evaluate the performance of hearing aids. A pure-tone audiometer is used primarily to obtain air-conduction and bone-conduction thresholds of hearing. These thresholds are helpful in the diagnosis of hearing loss. Pure-tone screening tests are employed extensively in industrial and school hearing conservation programmes.

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