The science of what you hear

Ever wonder how that tree falling in the forest becomes a sound? Sounds are atmospheric vibrations that travel through the air into your ears. Your ears can detect and decode tiny changes in the air pressure of only a few billionths of the atmospheric level. How they achieve this feat comes down to hair cells, your ears’ sensory receptors.

How hair cells work

Hair cells have tiny tufts of bristles that turn atmospheric vibrations into electrical currents that the brain can interpret.

How does this happen? The bristles consist of 20 to 100 fine cylindrical rods, with a fine filament connecting the rods together. As vibrations rock the rods back and forth, the filament opens a series of channels to allow millions of ions into the cell. The ions constitute an electrical current, which stimulates the cell, sending energy to the auditory nerve, which then transmits a signal to the brain.

The larger the wave, the longer the channel opens and the more ions enter, creating more energy and a “louder” sound. But how do we distinguish one sound from another?

The cochlea

Hair cells live inside the cochlea, a tiny organ resembling a snail’s shell. The cochlea splits complex sounds into component frequencies. For example, the cochlea mechanism can break down a piano chord note by note.

The cochlea's spiral construction allows different sound frequencies to travel specific lengths along the organ's tubes. So, each hair cell amplifies a particular frequency and ignores the rest. Ultimately, the 12,000 outer hair cells send this bundle of frequencies to the brain, which interprets a sound. This process allows us to distinguish between voices, instruments or birds.

The active process

Your ears also have a mechanism called the active process, which enables your ears to organize sounds. The process amplifies sound in quiet environments and shuts down in noisy environments. How it works is still a bit of mystery to scientists. However, we know that when the active process fails, it can lead to impaired hearing and the need for hearing aids.

What the future holds

When human hair cells die, they’re gone for good, which can result in hearing loss. Seeking a way to regenerate hair cells in humans, scientists are trying to decode the molecular signals other animals use for hair cell regeneration. Further research aims to gain a better understanding of the active process.

Hearing tests and hearing aids in Calgary

At Soundwave Hearing Care, we provide hearing tests and hearing aids so you can experience a full range of sounds. Visit one of our experienced audiologists in Calgary, Lethbridge, Grande Prairie or High River. Contact us today to book your appointment.