Question

How can we hear, for example, 50Hz sound waves when its wave length is several times the length of our ears?

Answer 1

Hearing is the perception of sound, which is the result of pressure waves traveling through a medium, such as air. While it is true that a 50Hz sound wave has a relatively long wavelength (approximately 6.8 meters or 22.3 feet in air), we can still hear it due to the remarkable sensitivity and frequency range of our auditory system.

The human ear can detect sound waves with frequencies ranging from around 20Hz to 20,000Hz (20kHz), with the most sensitive range being between 2kHz and 5kHz. When a sound wave with a frequency of 50Hz enters our ears, it sets in motion the auditory process:

1. Sound waves are collected and channeled by the outer ear (pinna) and then directed into the ear canal.
2. The sound waves cause the eardrum (tympanic membrane) to vibrate. The eardrum, being thin and flexible, can respond to a wide range of frequencies, including those with relatively long wavelengths like 50Hz.
3. These vibrations are then transmitted to the three small bones in the middle ear: the hammer (malleus), anvil (incus), and stirrup (stapes).
4. The bones in the middle ear amplify the vibrations and transfer them to the oval window, a membrane that separates the middle ear from the fluid-filled cochlea of the inner ear.
5. The cochlea, a spiral-shaped structure in the inner ear, contains fluid and hair cells. The vibrations cause the fluid to move, and this movement stimulates the hair cells.
6. The hair cells convert the mechanical vibrations into electrical signals that travel through the auditory nerve to the brain.
7. The brain processes these electrical signals, enabling us to perceive and interpret the sound.

Even though the wavelengths of lower-frequency sounds can be longer than the physical size of our ears, the intricate design of the ear allows us to perceive a wide range of sound frequencies. However, it's worth noting that the efficiency of hearing higher-frequency sounds tends to decline with age, as the sensitivity of the hair cells decreases. This is one of the reasons why older individuals may have difficulty hearing certain high-pitched sounds.