The Structure of Ear & Hearing Range
What is Sound?
Sound is a form of energy, just like electricity, heat or light. When you strike a bell, it makes a loud ringing noise. Now instead of just listening to the bell, put your finger on the bell after you have struck it. Can you feel it shaking? This movement or shaking, i.e. the to and fro motion of the body is termed as Vibration. The sound moves through a medium by alternately contracting and expanding parts of the medium it is travelling through. This compression and expansion creates a minute pressure difference that we perceive as sound. Let’s take a look at one of our five senses .i.e, Hearing.
Sound Wave (Longitudinal Wave) Travelling
Hearing is a sense endowed to us, thanks to the presence of the human auditory system. This auditory system gives us the ability to perceive sound by detecting vibrations in the surrounding medium. The vibration as mentioned earlier consists of minute pressure variations. How the human ear converts pressure difference into a perception is fascinating. We will now take a closer look at how this is achieved. We are going to start where a sound wave would start and follow it on its journey from outside of our ear all the way to our brain.
When you see someone, all you see is a very small part of a very complex mechanism. The flaps of cartilage are known as the Pinna. These folds of cartilage help reflect the incoming sound waves and also affect its intensity. This effect allows the brain to figure out direction of the source of the sound. The pinna is the opening to the ear Canal. The ear canal is a small cylindrical tube about 2.5 centimetres long. This canal leads to a vibrating membrane commonly known as eardrum. The eardrum marks the beginning of middle Ear.
The sound waves striking the eardrum create a vibration in the air filled cavity of the middle ear. The sound waves are in the form of pressure differences and are transferred from here to the cochlea in the inner ear by the means of three of the smallest bones in the Human Body. They are called Malleus (Hammer), Incus (Anvil) and Stapes (Stirrups). Stapes takes the award for the smallest bone in the human body. The sound here is still in wave form. The sound information is transferred to the Cochlea in the Inner Ear.
Cochlea consists of several fluid-filled sac like structures. The ear structures are covered with tiny hair and these convert the wave information into a form that we can understand. It is here that the sound wave is converted into nerve impulses that is sent to the brain via the auditory nerve. This electrical impulse is perceived by us that leads to our sense of hearing.
So while it seems you can hear a sounds immediately, it travels a long way before it is understood and becomes hearing. Hearing is the ability to perceive sound by detecting the minute changes in pressure. This done with the help of organs such as ear. It is one of our five sense and it defines how we see and experience the world around us.
Hearing Range refers to the range of frequencies that can be detected or heard by human or any other animal in consideration. The human ear and auditory system can detect frequencies between 20 Hz to 20,000 Hz. This range is different for different animals. Dolphins for example can hear sound waves of frequencies up to 100 kHz.