Did you know your ear works similarly to a guitar amplifier and a reverse piano at the same time? Keep reading to find out how this works.
The finely tuned human ear and listening system is not just a passive receiver of sound as you may normally think. It can selectively adjust and amplify sounds (similar to gain) based on the noise and characteristics of the surrounding environment.
The human ear is a complex, vital organ and an imperative tool. The ear acts as both a listening instrument and an active, adaptive amplifier, similar to the kind found in audio equipment. The human ear has the ability to conditionally amplify based on factors like focus and ambient sound levels.
The Human Ear: An Adaptive Amplifier
In The Energetic Ear (American Academy of Arts & Sciences available through MIT) A.J. Hudspeth described the human ear based on its ability to hear and distinguish tones at different frequencies. The cone-shaped ear can differentiate between sound patterns from music or decipher various phonemes and recognize speech patterns from voices. Your ability to tell the difference between tones and frequencies helps you do something as ordinary as tell the difference between voices and speakers in a podcast. As covered in Hudspeth’s journal article (which is related to his body of work), when in a quiet environment attempting to discern a particularly faint sound your ears enter into a active amplification mode (positive feedback loop like an amp with gain) trying to allow you to hear better. It’s an active amplification mode because just like a PA system or speaker, your ears actively use energy for the amplification process to change the original sound making it louder. At the limits of human hearing in quiet environments, Hudspeth states that our “acoustic sensitivity is enhanced more than a hundredfold by the active process operating at its highest gain.” Many trained listeners can pick apart and focus on particular sounds within a wall of sound as well. Speaking of a wall of sound, when you are in a loud environment your ears turn to a more passive mode as amplification is not needed and may indeed may be harmful.
The CDC states that excessive noise is one of the leading contributors to hearing loss, hence the importance of frequency discrimination in the ear. While pianos bring sounds from different strings together, the ear’s cochlea works to separate sounds into individual tonal constituents. Your ears are essentially anti-pianos working in exactly the opposite way. The cochlea has 20,000 hair cells that amplify sound, identify speech and parse complex and even muted sounds. Sounds produced can resonate because of amplified vibrations. Vibrations produce tiny and compressed pulses of air and these air molecules bump up against other air molecules until they get into the ears. For low-pitched sounds, the ear can detect as few as 20-pulses a second and for high-pitched sounds, as much as 20,000-pulses a second.
The ear canal works to channel sound waves that come into the eardrum, the tympanic membrane, which vibrates when a sound comes in and movements are passed into the tiny bones in the middle ear. The middle ear includes the amplifier, the bony prominence that works with the basilar membrane to maximize sound vibrations to compress them as they pass into the ear. To amplify sound, three tiny bones or ossicles, are used. The first bone is the hammer (malleus), which passes vibrations to the anvil (incus), and then onto the stapes before the “foot plate” on the stirrup opens the inner ear. Because the ear can change amplification, surface noise and vibrations are greater than at the foot plate to the stirrup which results in more than a 20-fold pressure increase. As the foot plate moves, it produces waves in the fluid located in the inner ear. It’s a delicate balance that takes place in the inner workings of the ear.
One of the reasons that hearing aids work is they mirror the intricate workings of the ear. They are either digital to convert sound waves into codes before amplifying them or they are analog to turn sound waves into electrical impulses that are then amplified. Hearing aids have three parts: a speaker, microphone and amplifier. Sound comes into the microphone, converted into waves and is then carried to the amplifier which increases the signal and sends it into the ear as a speaker. Hair cells that detect vibrations in sound convert data into neural signals that go to the brain. That’s why hair cells in the cochlea are important to hearing.
The ears are such amazing instruments. It’s no wonder they are compared to audio equipment based on their abilities to process and amplify sound. Just like the ears work to differentiate sound, audio differentiation is important to Backtracks.
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