Written By: Yang
Sound plays an important role in my everyday life. From apparent sounds like the radio and morning alarm to unnoticed sounds like the affirming click of the shutting door. I really couldn’t live without it. This makes me wonder: what is sound? And how am I able to hear it?
Sound – Vibrations in the Air
Sound is a form of energy, produced by the vibration of air molecules. In order to make sound, an object, such as a drum or vocal cords, must vibrate and push against the surrounding air. These vibrations cause the air to expand and compress, creating areas of high and low pressure that become sound waves.
The pitch and loudness of sound waves are determined by the wave’s wavelength and amplitude. The wavelength of a wave is the distance between an area of high pressure and the next. The faster the sound waves past a given point, the shorter the wavelength. Wavelength determines pitch. The shorter the wavelength, the higher the pitch. High pitched sounds include a whistle and fireworks, while low pitched sounds include frog noises and bells. However, the loudness of a sound comes from the amount of pressure between the air molecules. The more an object and the air around it vibrates, the more the air molecules “squeeze”, increasing the amplitude and creating a louder sound. The amplitude, wavelength, and corresponding areas of high and low air pressure are represented by the graph below.
The most common forms of sound production heard daily come from people’s voices and music speakers. Humans produce sound from the vocal cords within the larynx. When speaking, exhaled air causes an increase in pressure and vibrates the vocal cords, creating sound. This sound travels through the vocal tract, mouth, lips, tongue, and finally teeth to form speech. Speakers create sound by using electric currents and a magnetic field within to vibrate a voice coil.
Perceiving Sound Waves
Humans are able to hear sounds because of tiny bones and hairs in the ear. Firstly, sound waves travel into the ear through the ear canal, hitting the eardrum. The eardrum, as well as the ossicles situated further into the ear, begin to vibrate due to the incoming sound waves. These vibrations travel into the inner ear to the cochlea. Hair cells inside the cochlea detect the vibrations and convert them into electrical signals. These electrical signals travel to the brain via the auditory nerve, which processes them into recognizable sounds that allow someone to hear.
I cannot imagine not being able to jam out to my favourite tunes while doing homework or relaxing in the house. Interesting to think these sounds are just oscillating air, vibrating the tiny bones and hairs within my ears!