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MCAT

Unit 3: Lesson 1

Chemical and physical sciences practice passage questions

Clinical applications of tuning forks

Problem

Tuning forks are an effective tool clinicians can employ to test a patient’s hearing, but this goes beyond the simple task of being able to hear a tone. Because hearing is a function of both mechanical components of the ossicles and neural components of the cochlea, hearing loss can be either conductive (a complication with the physical aspect of hearing), or sensorineural (a problem with the neural component of hearing). Sensorineural hearing loss can result in the loss of ability to hear specific frequencies of sound. For example, most humans will lose their ability to hear high frequencies as they age. Conductive hearing loss generally causes decreased perception of all frequencies of sound.
A physician can utilize the simple physics of a tuning fork to determine whether hearing loss is conductive or sensorineural using the Weber and Rinne tests. The Weber test involve placing a tuning fork’s base in the center of a patient’s forehead. If a patient has unilateral conductive hearing loss, the sound from the tuning fork will seem louder in the affected ear. This is because the sound waves travel through bone and bypass the conduction of sound through air.
The Rinne test takes advantage of this phenomena as well; instead of the forehead, a tuning fork is held on the mastoid process just behind the ear. Once a patient is no longer able to hear it via bone conduction, the clinician then removes the fork from the bone, and hold the tuning fork closer to their ear. Because hearing is more sensitive to air conduction, a patient with normal hearing should still be able to hear the tuning fork. If they cannot hear it, this illustrates that the patient’s bone conduction is better than their air conduction, indicating that passage of sound to the inner ear is being inhibited. This suggests the patient has conductive hearing loss.
Two tuning forks of frequencies 440 Hz and 444 Hz are struck, one is held on a patient’s forehead, and the other is held away from their ear at a distance of 5 cm. What is the beat frequency produced by the two sound waves?
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