Test: Physiology of Hearing and Audiology - 1 - NEET PG MCQ

• Whenever there is a sound of 70–100 dB above the hearing threshold of the person, the stapedial reflex gets activated which does not allow a high intensity sound to damage the inner ear thereby protecting the inner ear from noise trauma.
• The transformer action of the middle ear reduces the impedance (resistance) and increases the admittance of sound, thereby amplifying the sound intensity during normal hearing.

• The handle of malleus is 1.3 times longer than the long process of incus so that the lever ratio is 1.3:1.
• 17: 1 is the Areal ratio
• 22 is the total transformer ratio of middle ear (Areal ratio × lever ratio)

• Bekesy evolved his travelling-wave theory for which he received the Nobel Prize.
• Helmholtz detected the sound amplifying effect of the eardrum and the auditory ossicles.
  Furthermore, he developed the resonance–theory of the perception of pitch in the inner ear. This theory postulates that specific frequencies are displayed on definite locations of the cochlea of the inner ear (place theory of pitch perception). This was replaced by the travelling wave theory by Georg v. Békésy

• From pinna to foot plate of stapes occurs the conduction of sound. So this is the conductive pathway and any defect here will lead to a conductive deafness.
• While travelling in an aeroplane, sudden changes in pressure during descent, leads to forceful closure of the Eustachian tube and tympanic membrane retraction leading to temporary conductive hearing loss and earache. This can be overcome by Valsalva manoeuvre.
• Trauma to labyrinth will lead to SN hearing loss.
• Noise induced hearing loss is associated with pathological changes in cochlea leading to SN hearing loss.

• Old age (presbycusis) leads to SN hearing loss.
• Loud noise induced hearing loss is associated with pathological changes in cochlea leading to SN hearing loss. Noise trauma, presbycusis and ototoxic drugs involve basal turns of cochlea first; thereby affect high frequency sounds early.
• Cochlear otosclerosis leads to sensory hearing loss.

• The tuning fork tests are most commonly done with 512 Hz (or FPS, i.e. frequency per second) sound frequency producing forks because these are better heard.
• Tuning forks with frequency less than 512 have more of vibration sense and those with frequency above 512 dampen very fast because of which comparison is not possible.

• Tympanosclerosis being a conductive pathology so BC > AC so Rinne will be negative.
• All the other options being SN deafness so AC > BC so Rinne will be positive.

• CSOM being a conductive pathology so BC > AC so Rinne will be negative.
• All the other options being SN deafness so AC > BC so Rinne will be positive.

• Presbycusis being a SN pathology so AC > BC so Rinne will be positive.
• All the other options being conductive deafness so BC > AC so Rinne will be negative.

• Rinne is said to be positive when AC > BC.
• In normal ear air conduction is more than the bone conduction due to the transformer action of the middle ear.
• All the other options are conductive deafness conditions so BC > AC, i.e. Rinne will be negative.

• Middle ear pathology indicates conductive deafness so Weber will be lateralised to the right side in the right ear pathology, i.e. towards the worst side.
• Weber is lateralised to the Worst ear in Conductive hearing loss and Better ear in Sensorineural hearing loss.

• Threshold for bone conduction is normal means that the sensorineural pathway is normal.
• Threshold for air conduction is increased means conductive hearing loss.

So this is indicative of middle ear disease.