We take for granted that we can hear voices, songs and our favourite shows via various streaming services. How does sound occur, what is sound, and what happens when we can’t hear? Here we will discuss these questions and explain the magic of sound.
Sound is created when something emits energy in the form of a vibration (i.e. moving backwards and forwards rapidly). If you were to pull a guitar string, when you then release the tight string, the potential energy becomes vibrational energy. This causes the air around it to vibrate as well and moves the energy outwards from the source in all directions, extending to vibrating the air in your ear: that is when we start to hear the sound. How do we use this sound though?
There are two aspects to how we perceive sound: physical and psychological. The physical aspect does what it says on the tin, it is the physical movement or action that caused the sound (i.e. hitting a drum etc.). Then there is the psychological aspect. This is the process which occurs in our ears and brains to convert those vibrational waves into the sound we interpret as voices, music etc.
Our ears consist of tiny bones, tubes and membranes (such as our ear drum), helping to process the sound waves to send to our brains. Our ears are funnel shaped, making them adapted to collecting and filtering the sound waves, guiding them towards the ear drum. Once the waves reach the ear drum (in the outer ear), they cause the drum to vibrate. This makes the tiny bones (in the middle ear) move, whilst the last bone in the chain ‘knocks’ on the membrane in front of the cochlea (in the inner ear), making the fluid in the cochlea move. The fluid movement triggers an electrical response in the hearing nerve, which can be processed by our brain.
(Image credit to: https://www.hearinglink.org/your-hearing/about-hearing/how-the-ear-works/)
All of this happens in 0.05 seconds, that is 10 times faster than blinking. The speed of light may be faster than the speed of sound, but our ears work faster than our eyes, making hearing our fastest sense.
What happens when you are, or become deaf? There are numerous causes of hearing loss or deafness. People can become deaf suddenly as a complication of a virus, or lose hearing over time due to disease, nerve damage, or injury caused by noise. Noise–induced hearing loss happens as a result of acute or sustained exposure to very loud noises. For example, if you are at a loud concert the hair cells in your ear can become over-stimulated. In response to this, the body sends oxygen to this region, causing the death of the cell (i.e. oxidative cell death). Noise-induced hearing loss usually makes it harder to hear lower pitched sounds, such as those between 3 and 6kHz. There are two main types of hearing loss: Conductive and Sensorineural hearing loss. The first happens when something blocks sound waves from reaching the inner ear, whereas sensorineural hearing loss is caused by damage to the inner ear or to the nerves that send sound to the brain, and this is more likely to be permanent.
There is also the inability to hear high frequency (i.e. high pitched) sounds. Pitch is dependent on how many times the eardrum is compressed per second. Did you know that shops sometimes use high pitched sounds (i.e. the Mosquito sound) to deter teenagers from loitering, but you haven’t heard it? Some children cottoned on and set this sound as a ringtone so teachers couldn’t hear if they received texts in class. As we age we lose the ability to hear higher frequency sounds. This process is called presbycusis (a mouthful), and can be seen in those as young as 18. Presbycusis is completely natural and occurs as the cells in our ears age, making it unavoidable. The average adult can hear sounds between 0.02 and 16kHz, but the high pitched sound of the Mosquito noise is at 17.4kHz, making it hard for some people to hear it.
I’m sure there are many sounds in this world we would happily live without, li ke car horns or the sound of building work outside our office window. However, sound is something we take for granted every day. Listening to the radio, a podcast, TV in the morning, talking to a friend, or humming our favourite tune. Without our amazing ears, processing this information in 0.05 seconds all day, every day, we would miss an awful lot. Take care of these wonder machines!