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BC-HIS practice questions

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Question 1Basic Sciences and Acoustics

Which structure in the outer ear primarily funnels sound waves toward the tympanic membrane?

  1. The ossicular chain
  2. The pinna and ear canal Correct answer.
  3. The cochlear duct
  4. The oval window

Explanation

The pinna and external auditory canal collect and direct acoustic energy toward the tympanic membrane. The ossicles and oval window are middle-ear structures that transmit vibration, and the cochlear duct is part of the inner ear.

Question 2Basic Sciences and Acoustics

Sound is best described as which of the following?

  1. A beam of electromagnetic radiation
  2. A stream of charged particles
  3. A static electric field
  4. A pressure wave traveling through a medium Correct answer.

Explanation

Sound is a mechanical longitudinal wave consisting of alternating compressions and rarefactions in a medium such as air. It requires a medium and is not electromagnetic or electrostatic in nature.

Question 3Basic Sciences and Acoustics

Doubling the sound pressure level of a signal corresponds to an increase of approximately how many decibels?

  1. 6 dB Correct answer.
  2. 10 dB
  3. 3 dB
  4. 20 dB

Explanation

Decibels for pressure use 20 log10 of the pressure ratio, so doubling pressure gives 20 log10(2) ≈ 6 dB. A 3 dB change corresponds to doubling acoustic power, not pressure.

Question 4Basic Sciences and Acoustics

The frequency range of normal human hearing is most commonly cited as which of the following?

  1. 200 Hz to 2 kHz
  2. 20 Hz to 20 kHz Correct answer.
  3. 1 Hz to 1 kHz
  4. 2 kHz to 50 kHz

Explanation

Human hearing typically spans roughly 20 Hz to 20 kHz, narrowing with age at the high end. The speech range occupies a smaller portion of this span.

Question 5Basic Sciences and Acoustics

Which ossicle is directly attached to the tympanic membrane?

  1. The cochlea
  2. The malleus Correct answer.
  3. The incus
  4. The stapes

Explanation

The malleus is embedded in the tympanic membrane and transfers vibration to the incus and then the stapes. The stapes contacts the oval window, and the cochlea is an inner-ear organ.

Question 6Basic Sciences and Acoustics

A sound wave with a frequency of 500 Hz has a period of which value?

  1. 5 ms
  2. 2 ms Correct answer.
  3. 20 ms
  4. 0.5 ms

Explanation

Period is the reciprocal of frequency, so 1/500 s equals 0.002 s, or 2 ms. The other values correspond to different frequencies.

Question 7Basic Sciences and Acoustics

The acoustic reflex is mediated primarily by contraction of which muscle?

  1. The tensor tympani only
  2. The stapedius muscle Correct answer.
  3. The levator veli palatini
  4. The cricothyroid muscle

Explanation

The stapedius muscle contracts in response to loud sound and stiffens the ossicular chain, reducing transmission. The tensor tympani can also contract but the stapedius is the principal mediator of the acoustic reflex in humans.

Question 8Basic Sciences and Acoustics

The traveling wave on the basilar membrane reaches its maximum amplitude at a location determined primarily by which factor?

  1. The intensity of the stimulus
  2. The phase of the stimulus
  3. The duration of the stimulus
  4. The frequency of the stimulus Correct answer.

Explanation

Tonotopic organization means high frequencies peak near the base and low frequencies near the apex of the cochlea. Intensity affects amplitude but not the characteristic place of peak vibration.

Question 9Basic Sciences and Acoustics

Which inner-ear structure contains the sensory hair cells responsible for hearing?

  1. The saccule
  2. The organ of Corti Correct answer.
  3. The utricle
  4. The semicircular canals

Explanation

The organ of Corti, situated on the basilar membrane within the cochlea, houses the auditory hair cells. The semicircular canals, utricle, and saccule are vestibular structures.

Question 10Basic Sciences and Acoustics

In a pure-tone audiogram, hearing threshold level is referenced to which standard?

  1. The maximum output of the audiometer
  2. The average threshold of normal-hearing listeners Correct answer.
  3. The patient's uncomfortable loudness level
  4. The patient's most comfortable level

Explanation

Hearing level in dB HL is normalized to the average threshold of otologically normal young adults. This allows thresholds to be plotted relative to a common reference across frequencies.

Question 11Basic Sciences and Acoustics

A hearing loss in which air-conduction thresholds are poorer than bone-conduction thresholds by a consistent margin is classified as which type?

  1. Central
  2. Conductive Correct answer.
  3. Mixed
  4. Sensorineural

Explanation

An air-bone gap with normal bone-conduction thresholds indicates a conductive loss, where sound is attenuated before reaching the cochlea. Sensorineural loss shows air and bone thresholds that are similarly reduced.

Question 12Basic Sciences and Acoustics

Which physical property of a medium most directly determines the speed of sound through it?

  1. Its temperature only
  2. Its color
  3. Its volume
  4. Its elasticity and density Correct answer.

Explanation

Sound speed depends on the medium's stiffness (elastic modulus) and density, with stiffer and less dense media generally transmitting sound faster. Temperature matters mainly because it alters these properties.

Question 13Basic Sciences and Acoustics

Two tones of 1000 Hz and 1004 Hz are presented together. A listener perceives a slow fluctuation at 4 Hz, which is an example of which phenomenon?

  1. Reverberation
  2. Resonance
  3. Masking
  4. Beats Correct answer.

Explanation

Beats arise when two tones of slightly different frequency interact, producing amplitude fluctuation at the difference frequency. Resonance and reverberation involve system response and reflections, not this interference pattern.

Question 14Basic Sciences and Acoustics

Which unit is used to express sound intensity level?

  1. Pascal
  2. Decibel Correct answer.
  3. Watt per square meter
  4. Hertz

Explanation

Sound intensity level is a logarithmic ratio expressed in decibels. The pascal measures pressure and the watt per square meter measures intensity itself, not its level.

Question 15Basic Sciences and Acoustics

The term 'presbycusis' refers to which condition?

  1. Hearing loss from earwax impaction
  2. Hearing loss associated with aging Correct answer.
  3. Hearing loss from a perforated eardrum
  4. Hearing loss from acoustic neuroma

Explanation

Presbycusis is age-related sensorineural hearing loss, typically affecting high frequencies first. The other options describe conductive or retrocochlear causes unrelated to aging.

Question 16Basic Sciences and Acoustics

A signal has a sound pressure level of 60 dB. If its pressure is increased by a factor of 10, what is the new level?

  1. 70 dB
  2. 80 dB Correct answer.
  3. 600 dB
  4. 120 dB

Explanation

A tenfold pressure increase adds 20 log10(10) = 20 dB, so 60 dB becomes 80 dB. Adding 10 dB would correspond to a power increase of tenfold, not pressure.

Question 17Basic Sciences and Acoustics

The impedance-matching function of the middle ear is achieved mainly by which combination?

  1. The stiffness of the round window and the cochlear fluid
  2. The length of the ear canal and the pinna shape
  3. The area ratio of the tympanic membrane to the stapes footplate and the ossicular lever Correct answer.
  4. The mass of the basilar membrane and hair cell density

Explanation

The large tympanic membrane area relative to the small stapes footplate, together with the ossicular lever, boosts pressure at the oval window to overcome the fluid impedance of the cochlea. Other listed factors relate to collection, inner-ear mechanics, or transduction.

Question 18Basic Sciences and Acoustics

Which frequency region is typically most important for speech intelligibility?

  1. Above 8 kHz
  2. Below 250 Hz
  3. Around 15 kHz
  4. Around 500 Hz to 4 kHz Correct answer.

Explanation

Most speech energy and consonant cues that support intelligibility lie roughly between 500 Hz and 4 kHz. Very low and very high frequencies contribute less to understanding speech.

Question 19Basic Sciences and Acoustics

In psychoacoustics, the just-noticeable difference for frequency is smallest at which condition?

  1. Mid frequencies at moderate intensity Correct answer.
  2. Very high frequencies near threshold
  3. Low frequencies at high intensity
  4. High frequencies at low intensity

Explanation

Frequency discrimination is most acute in the mid-frequency range at moderate levels, where pitch cues are strongest. Discrimination worsens at very low or very high frequencies and near threshold.

Question 20Basic Sciences and Acoustics

Which membrane separates the middle ear from the inner ear at the oval window?

  1. The tectorial membrane
  2. Reissner's membrane
  3. The basilar membrane
  4. The stapes footplate and annular ligament Correct answer.

Explanation

The stapes footplate, sealed by the annular ligament, sits in the oval window and transmits vibration into the cochlear fluids. The basilar, tectorial, and Reissner's membranes are internal cochlear structures.

Question 21Basic Sciences and Acoustics

A room with a long reverberation time most directly impairs which aspect of listening?

  1. Temporal separation of successive speech sounds Correct answer.
  2. Detection of very quiet sounds
  3. The ability to perceive low frequencies
  4. The perception of loudness at high levels

Explanation

Long reverberation causes each sound to persist and overlap with following sounds, smearing temporal cues important for speech. Reverberation does not primarily raise thresholds or alter loudness perception.

Question 22Basic Sciences and Acoustics

Which statement correctly describes the relationship between wavelength, frequency, and speed of sound?

  1. Wavelength is independent of frequency
  2. Wavelength equals speed divided by frequency Correct answer.
  3. Wavelength equals speed multiplied by frequency
  4. Wavelength equals frequency divided by speed

Explanation

The wave equation gives wavelength as the speed of sound divided by frequency. Higher frequency therefore yields shorter wavelength for a fixed speed.

Question 23Basic Sciences and Acoustics

Otoacoustic emissions are produced by which mechanism?

  1. Passive vibration of the tympanic membrane
  2. Active motility of outer hair cells Correct answer.
  3. Contraction of the stapedius muscle
  4. Movement of the ossicular chain alone

Explanation

Outer hair cells actively change length and amplify cochlear motion, generating emissions that can be recorded in the ear canal. The other structures are passive or reflexive and do not generate emissions.

Question 24Basic Sciences and Acoustics

A listener reports that a 40 dB HL pure tone at 4000 Hz is inaudible while a 40 dB HL tone at 500 Hz is heard clearly. Which cochlear region is most likely impaired?

  1. The basal region Correct answer.
  2. The helicotrema
  3. The vestibular apparatus
  4. The apical region

Explanation

High frequencies are encoded at the base of the cochlea, so a high-frequency deficit localizes to basal damage. The apex encodes low frequencies, which remain intact in this case.

Question 25Basic Sciences and Acoustics

Which factor most increases the risk of noise-induced hearing loss?

  1. Higher intensity and longer exposure duration Correct answer.
  2. Intermittent exposure at low levels
  3. Lower intensity with brief exposure
  4. Exposure to low-frequency sound only

Explanation

Noise-induced hearing loss depends on both the level of sound and the duration of exposure, with risk rising as either increases. Low-level or brief exposures carry much less risk.

Question 26Basic Sciences and Acoustics

In a normal ear, sound waves are transmitted from the middle ear to the inner ear primarily through which structure?

  1. The eustachian tube
  2. The oval window Correct answer.
  3. The tympanic membrane
  4. The round window

Explanation

The oval window is the membrane-covered opening that connects the middle ear to the vestibule of the inner ear, and it is the primary pathway for sound transmission. The round window acts as a pressure relief valve, while the eustachian tube equalizes pressure and the tympanic membrane receives sound from the ear canal.

Question 27Basic Sciences and Acoustics

A sound wave has a frequency of 2000 Hz. What is its period?

  1. 0.5 ms Correct answer.
  2. 5 ms
  3. 0.2 ms
  4. 2 ms

Explanation

The period is the reciprocal of frequency. For 2000 Hz, period = 1/2000 seconds = 0.0005 s = 0.5 ms.

Question 28Basic Sciences and Acoustics

Which type of hearing loss is characterized by normal bone-conduction thresholds and abnormal air-conduction thresholds?

  1. Mixed hearing loss
  2. Conductive hearing loss Correct answer.
  3. Central auditory processing disorder
  4. Sensorineural hearing loss

Explanation

In conductive hearing loss, air-conduction thresholds are elevated while bone-conduction thresholds remain normal because the inner ear function is preserved. Sensorineural loss affects both air and bone conduction, and mixed loss shows both components.

Question 29Basic Sciences and Acoustics

A sound has an intensity of 10^-6 W/m². What is its intensity level in decibels (dB IL)? (Reference intensity = 10^-12 W/m²)

  1. 6 dB
  2. 120 dB
  3. 60 dB Correct answer.
  4. 0 dB

Explanation

Intensity level in dB is calculated as 10 log10(I/I0). Substituting I = 10^-6 and I0 = 10^-12 gives a ratio of 10^6, and 10 log10(10^6) = 10 × 6 = 60 dB.

Question 30Basic Sciences and Acoustics

A listener with normal hearing is asked to detect a 1000 Hz tone in the presence of a broadband noise. If the noise level is increased while the tone level is held constant, what happens to the tone's detectability?

  1. It increases because the noise masks competing frequencies
  2. It increases because the noise enhances temporal integration
  3. It decreases because the signal-to-noise ratio is reduced Correct answer.
  4. It remains unchanged because the tone frequency is fixed

Explanation

Detectability depends on the signal-to-noise ratio (SNR). Increasing noise while keeping the signal constant lowers the SNR, making the tone harder to detect. Masking occurs when noise interferes with the signal, and a lower SNR means poorer detection.

Question 31Anatomy and Physiology of the Auditory System

Which structure separates the external ear canal from the middle ear cavity?

  1. The round window
  2. The Eustachian tube
  3. The tympanic membrane Correct answer.
  4. The oval window

Explanation

The tympanic membrane forms the boundary between the external auditory canal and the middle ear space, vibrating in response to sound and transferring energy to the ossicles. The oval and round windows are middle-ear structures opening into the inner ear, and the Eustachian tube connects the middle ear to the nasopharynx.

Question 32Anatomy and Physiology of the Auditory System

The three ossicles of the middle ear, in order from the tympanic membrane to the inner ear, are:

  1. Incus, malleus, stapes
  2. Malleus, stapes, incus
  3. Stapes, incus, malleus
  4. Malleus, incus, stapes Correct answer.

Explanation

Sound travels from the tympanic membrane through the malleus, then the incus, and finally the stapes, whose footplate sits in the oval window. This chain provides impedance matching between air and cochlear fluids.

Question 33Anatomy and Physiology of the Auditory System

Which cranial nerve carries the primary afferent fibers from the cochlea to the brainstem?

  1. Facial nerve (CN VII)
  2. Trigeminal nerve (CN V)
  3. Vestibulocochlear nerve (CN VIII) Correct answer.
  4. Glossopharyngeal nerve (CN IX)

Explanation

Auditory and vestibular afferents travel in the vestibulocochlear nerve, cranial nerve VIII. Its cochlear division synapses in the cochlear nucleus of the brainstem.

Question 34Anatomy and Physiology of the Auditory System

The scala media (cochlear duct) is filled with which fluid?

  1. Endolymph Correct answer.
  2. Perilymph
  3. Plasma
  4. Cerebrospinal fluid

Explanation

The scala media contains endolymph, a potassium-rich fluid that bathes the hair cells and establishes the endocochlear potential. Perilymph fills the scala vestibuli and scala tympani.

Question 35Anatomy and Physiology of the Auditory System

The organ of Corti rests on which structure within the cochlea?

  1. Reissner's membrane
  2. The basilar membrane Correct answer.
  3. The tectorial membrane
  4. The spiral ligament

Explanation

The organ of Corti sits on the basilar membrane, and its hair cell stereocilia contact the overlying tectorial membrane. Movement of the basilar membrane relative to the tectorial membrane deflects the stereocilia.

Question 36Anatomy and Physiology of the Auditory System

Which muscle contracts to dampen movement of the stapes in response to loud sound?

  1. Stapedius Correct answer.
  2. Levator veli palatini
  3. Tensor tympani
  4. Posterior auricular

Explanation

The stapedius muscle, innervated by the facial nerve, contracts to reduce stapes motion as part of the acoustic reflex. The tensor tympani instead pulls on the malleus.

Question 37Anatomy and Physiology of the Auditory System

The pinna and external auditory canal together make up which portion of the auditory system?

  1. The middle ear
  2. The inner ear
  3. The conductive portion of the outer ear Correct answer.
  4. The central auditory pathway

Explanation

The pinna and ear canal form the outer ear, which conducts sound to the tympanic membrane and provides modest resonance gain. The middle ear and inner ear lie deeper and perform separate transduction functions.

Question 38Anatomy and Physiology of the Auditory System

The cochlea's spiral shape completes approximately how many turns in humans?

  1. About one-half turn
  2. About one-quarter turn
  3. About five turns
  4. About two and one-half turns Correct answer.

Explanation

The human cochlea coils approximately two and one-half to two and three-quarter turns around its modiolus. This length supports a tonotopic arrangement from base to apex.

Question 39Anatomy and Physiology of the Auditory System

A tone is detected at the base of the cochlea. Which frequency range is most consistent with this location?

  1. High frequencies near 8000 Hz Correct answer.
  2. Low frequencies near 250 Hz
  3. All frequencies equally
  4. Frequencies below 100 Hz

Explanation

The basilar membrane is narrow and stiff at the base, so high frequencies produce peak displacement there. Low frequencies peak toward the apex.

Question 40Anatomy and Physiology of the Auditory System

A patient has a perforation of the tympanic membrane with no ossicular damage. What type of hearing loss is most likely?

  1. Central auditory processing disorder
  2. Conductive hearing loss Correct answer.
  3. Retrocochlear hearing loss
  4. Sensorineural hearing loss

Explanation

A tympanic membrane perforation reduces the efficiency of sound transfer to the cochlea, producing a conductive loss. The inner ear remains intact, so sensorineural function is preserved.

Question 41Anatomy and Physiology of the Auditory System

Why does the middle ear provide impedance matching between air and cochlear fluid?

  1. Because air and fluid have very different acoustic impedances, and direct transmission would lose most energy Correct answer.
  2. Because the cochlea requires electrical stimulation to function
  3. Because the Eustachian tube equalizes pressure during swallowing
  4. Because the ossicles amplify sound by a factor of one hundred

Explanation

Fluid is much denser than air, so without matching most sound energy would reflect at the oval window. The areal ratio of the tympanic membrane to the stapes footplate and the lever action of the ossicles together overcome this mismatch.

Question 42Anatomy and Physiology of the Auditory System

In a normal ear, which structure vibrates in response to pressure waves in the scala vestibuli and ultimately stimulates the hair cells?

  1. The tensor tympani
  2. The semicircular canals
  3. The stapes footplate alone
  4. The basilar membrane Correct answer.

Explanation

Pressure waves in the cochlear fluids produce a traveling wave along the basilar membrane, deflecting it and shearing the stereocilia against the tectorial membrane. This mechanical displacement is the proximate stimulus for hair cells.

Question 43Anatomy and Physiology of the Auditory System

Outer hair cells differ from inner hair cells primarily in that outer hair cells:

  1. Function mainly as cochlear amplifiers through electromotility Correct answer.
  2. Detect only very low frequencies
  3. Are the main source of afferent auditory nerve fibers
  4. Are located in the vestibular apparatus

Explanation

Outer hair cells change length in response to electrical stimulation, providing active amplification and sharpening of the traveling wave. Inner hair cells provide the vast majority of afferent innervation and encode the signal sent to the brain.

Question 44Anatomy and Physiology of the Auditory System

The endocochlear potential is generated largely by which mechanism?

  1. Mechanical pressure from the ossicles
  2. Passive diffusion of sodium into the scala media
  3. Active potassium secretion by the stria vascularis Correct answer.
  4. Calcium influx through hair cell channels

Explanation

The stria vascularis actively pumps potassium into the endolymph, producing a positive potential of roughly 80 to 100 mV relative to surrounding fluids. This potential drives the transducer current through hair cells.

Question 45Anatomy and Physiology of the Auditory System

A lesion at the level of the superior olivary complex would most directly affect which function?

  1. Middle-ear impedance matching
  2. Vestibular control of posture
  3. Detection of very high frequencies at the cochlear base
  4. Binaural processing of interaural timing and level differences Correct answer.

Explanation

The superior olivary complex is the first major brainstem site receiving input from both ears, making it central to localizing sound via interaural time and intensity cues. Frequency analysis begins in the cochlea, and impedance matching is a middle-ear function.

Question 46Anatomy and Physiology of the Auditory System

The stapedius reflex is typically measured clinically for what purpose?

  1. To assess the integrity of the middle-ear reflex arc and identify retrocochlear pathology Correct answer.
  2. To measure the frequency range of the cochlea
  3. To evaluate vestibular function
  4. To determine the length of the external canal

Explanation

Acoustic reflex testing checks a circuit involving the cochlea, auditory nerve, brainstem, facial nerve, and stapedius muscle. Abnormalities can flag middle-ear, cochlear, or retrocochlear problems.

Question 47Anatomy and Physiology of the Auditory System

The medial geniculate body is part of which structure?

  1. The cerebellum
  2. The cochlea
  3. The medulla
  4. The thalamus Correct answer.

Explanation

The medial geniculate body is the auditory relay nucleus of the thalamus, projecting to the auditory cortex. It receives ascending fibers from the inferior colliculus.

Question 48Anatomy and Physiology of the Auditory System

A high-frequency sound produces maximal displacement at the base. Which physical property of the basilar membrane explains this?

  1. It lacks hair cells at the base
  2. It is narrower and stiffer at the base Correct answer.
  3. It is filled with endolymph at the base
  4. It is wider and more compliant at the base

Explanation

The basilar membrane is narrow and stiff near the base, so it resonates best at high frequencies. Toward the apex it widens and becomes more compliant, favoring low frequencies.

Question 49Anatomy and Physiology of the Auditory System

The Eustachian tube normally opens during swallowing or yawning in order to:

  1. Amplify low-frequency sound at the oval window
  2. Equalize pressure between the middle ear and the nasopharynx Correct answer.
  3. Drain endolymph from the scala media
  4. Transmit sound from the nasopharynx to the cochlea

Explanation

Brief opening of the Eustachian tube allows air to enter or leave the middle ear so that its pressure matches ambient pressure. This keeps the tympanic membrane and ossicles operating efficiently.

Question 50Anatomy and Physiology of the Auditory System

Which structure connects the middle-ear cavity to the nasopharynx?

  1. The Eustachian tube Correct answer.
  2. The cochlear aqueduct
  3. The external auditory canal
  4. The oval window

Explanation

The Eustachian tube runs from the middle ear to the nasopharynx and regulates middle-ear pressure. Its dysfunction is a common cause of middle-ear effusion.