How does hearing work?

From sound to auditory perception

The process of hearing is astonishingly complex and fascinating. The finely tuned mechanisms of our hearing enable us to experience the world’s rich variety of sounds. Our ear does not merely act as a passive receiver of sound; it processes incoming sound waves in an astonishing way to allow us to perceive sounds with precision. Find out more about the amazing capabilities of our auditory system.

The structure of the ear: three main parts for a unique function

The human ear consists of three main parts:

• the outer ear
• the middle ear
• the inner ear

These parts all play a crucial role in the process of hearing. But exactly how do they help us to perceive the sounds and noises around us?

The outer ear comprises the auricle and the ear canal. The auricle captures sound waves and directs them into the ear canal. The sound waves travel through the ear canal and strike the eardrum. These vibrations set the hearing process in motion. Just like a funnel directing water into a bottle, the outer ear directs sound deep into our ear.

The middle ear is home to three tiny bones: the malleus, incus and stapes - the ossicles. They form the smallest bone system in the human body and transmit sound waves from the air into the inner ear. This part also contains the tympanic cavity, an air-filled space that equalises the pressure between the outer and middle ear. This is where a connection is formed between the ear canal and the inner ear, a bridge that carries the sound.

The inner ear contains the cochlea. It is filled with fluid and contains thousands of hair cells. These tiny hairs react to the slightest movements and convert them into electrical signals.

The path of sound: from the outer ear to the brain

The path of sound from the outer ear to the brain can be imagined as a kind of relay race, in which the baton - in this case, the sound - is passed from one team member to the next. At every stage of the process, the sound changes and approaches its final form as a sound that our brain can recognise.

Step 1: Sound is picked up by the outer ear

The sounds around us are sound waves vibrating through the air. These waves strike the outer ear, are focused and directed into the ear canal.

Step 2: Transmission to the middle ear

The sound waves strike the eardrum and cause it to vibrate. These vibrations are transmitted to the ossicles, which amplify them and pass them on to the inner ear.

Step 3: Conversion into electrical signals in the inner ear

The vibrations reach the cochlea and cause the fluid inside it to move. The hair cells’ cilia follow this movement, which generates electrical impulses.

Step 4: Transmission of the impulses to the brain

The electrical signals generated are picked up by the auditory nerve and transmitted to the auditory centre in the brain. There, they are interpreted as sounds and tones. The auditory nerve acts like a messenger, carrying the messages from the hair cells to the brain.

Our hearing: frequencies and frequency ranges

The human ability to hear is impressive. We can perceive a wide range of frequencies. The normal frequency range that the human ear can cover lies between 20 Hz and 20,000 Hz. However, it is important to know that our hearing can deteriorate over time, which can lead to hearing loss.

Modern solutions for hearing: hearing aids

If hearing loss occurs at some point, whether due to age or illness, there are various aids that can improve hearing. Hearing aids, for example, amplify sound waves so that they can be more easily picked up and processed by the ear.

However, hearing aids are generally designed to amplify all sounds, meaning both speech and ambient noise. This can be particularly problematic when watching television.

For this reason, faller audio has developed the OSKAR TV sound amplifier for people with hearing loss. The portable speaker amplifies dialogue whilst watching TV and simultaneously filters out distracting background noise. This makes it a useful addition to a hearing aid.