It is not possible to see a globe without sound. For most of us, the sound is probably the first thing that we experience when we wake up in the morning – when we hear the birds chirp or when the alarm clock rings. The sound may also be the last thing that we hear at night as we listen to our heartbeat and gradually drift away into the quiet world of sleep. All in all, the sound is fascinating. In this article, let us take a closer look at the science of sound.
Defining Sound
Sound is the energy produced by objects when they vibrate. There are two different aspects to sound: there is a physical process that generates sound energy and sends it darting through the air, and there is a psychological process that happens inside our ears and intelligence, which change the received sound energy into the atmosphere which we understand as sound, communication, and music. In this article, we will be solely concentrating on the physical process of the sound.
Sound is a mechanical wave that arises from the back and forth movement of the particles of the medium through which the sound wave travels. If the noise waves travel from left to right in the air, the element of air will be moving both rightward and leftward as the force of the noise wave overtake through it. The motion of the particles is parallel to the direction of energy transport, and due to this property, the sound waves are characterized as longitudinal waves. The motion of the particles is parallel to the direction of energy transport, and due to this property, the sound waves are characterized as longitudinal waves.
Characteristics of Sound Waves
Following are a few prominent characteristics of sound waves:
- Wavelength – The distance travelled by sound during one vibration of the medium particle is known as the wavelength of the sound wave.
- Amplitude – The maximum displacement of the vibration of the medium particle from its equilibrium position is called the amplitude of the sound wave.
- Time Period – The time taken by the medium particle to complete vibration is known as the time period of sound waves.
- Frequency – The number of vibrations of the medium particle per second is known as the frequency of the sound wave.
Speed of Sound
The speed of sound is the reserves traveled for every unit moment by a noise wave as it propagates during an elastic medium. The speed of sound in air at 20 °C is 343 meters per second. The speed is highly dependent on the temperature and the medium through which the sound waves propagate. Sound travels slowly in gases, faster in liquids, and most quickly in gases. The table below lists the speed of sound in various mediums.
| State | Substance | Speed in m/s |
| Solids | Aluminium | 6420 |
| Steel | 5960 | |
| Iron | 5950 | |
| Glass | 3980 | |
| Liquids | Distilled Water | 1498 |
| Methanol | 1103 | |
| Ethanol | 1207 | |
| Seawater | 1531 | |
| Gases | Oxygen | 316 |
| Hydrogen | 1284 | |
| Sulphur Dioxide | 213 |
Fun Facts
- When the speed of the object exceeds the speed of sound, the speed of the respective object is known as supersonic speed. The speed of bullets and jet airplanes are considered supersonic speed.
- When a sound-producing source itself moves with a speed higher than that of sound, the source produces a shock wave. These shock waves produce a very sharp and loud sound known as the sonic boom.