Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
The human ear is a sensitive device that converts pressure variations in air at audible frequencies into electrical signals that travel to the brain via the auditory nerve.
The Outer Ear: Consists of the 'pinna' which collects sound and the auditory canal. At the end of the canal is a thin membrane called the ear drum or tympanic membrane.
The Middle Ear: Contains three tiny bones—the hammer (malleus), anvil (incus), and stirrup (stapes). These bones amplify the pressure variations received from the ear drum several times.
The Inner Ear: The amplified pressure variations are turned into electrical signals by the cochlea. These signals are then sent to the brain.
Mechanism: Compression in the sound wave increases pressure outside the eardrum, pushing it inward; rarefaction decreases pressure, pulling it outward, causing the membrane to vibrate.
Audible Range: The average human ear can hear sounds in the frequency range of to ().
📐Formulae
💡Examples
Problem 1:
A sound wave travels at a speed of . If its wavelength is , what is the frequency of the wave? Will it be audible?
Solution:
Given: , . Using , we get . Since , it is not audible to humans.
Explanation:
The frequency is calculated by dividing velocity by wavelength. Since the result exceeds the upper limit of human hearing (), it is classified as ultrasonic sound.
Problem 2:
What is the function of the three bones in the middle ear during the process of hearing?
Solution:
The hammer, anvil, and stirrup act as a lever system to amplify the vibrations of the tympanic membrane. The pressure variations are increased significantly before being passed to the inner ear.
Explanation:
Because the inner ear is filled with fluid, it requires more force to create waves than air does. The middle ear bones provide the necessary mechanical advantage to amplify the pressure variations by a factor of about or more.