WHAT IS SOUND?
Sound is a type of energy produced by vibrating objects and propagated in waves via various mediums such as air, water, and solids. It is essential for communication and perception, defining our worldview by letting us to detect and comprehend various frequencies and patterns.
Source of sound: The source of sound can only be a vibrating object. Sound is a form of energy that is merely a manifestation of the mechanical energy of vibrating objects.
Material medium: The propagation of sound requires some kind of physical medium. That is, sound cannot propagate through vacuum. Although sound travels from one place to another through a physical medium, the particles of the medium do not move from one place to another. Again, when a wave propagates from one place to another, the particles of the medium do not move. That is, sound and waves propagate through the medium in the same way. From the similar use of the two, it can be concluded that sound propagates through a medium in the form of waves.
Sound detector: Sound evokes the sense of hearing in the human ear. But there is a certain limit to the receptiveness of the ear. If the frequency of the sound wave hitting the ear is less than 20 Hz or more than 20000 Hz, it cannot cause any hearing sensation. So, the frequency range from 20 Hz to 20000 Hz is generally called the audible frequency range. However, it should be remembered that the above range is slightly different for different people. Generally, the ears of different animals detect sounds of different ranges.
WHAT IS SOUND?
Sound is a type of energy emitted by vibrating objects that propagates in the form of waves through an inert medium and produces a sense of hearing in the ears of most animals, including humans.
HOW SOUND IS PRODUCED?
When an object vibrates, it creates a pressure wave which results in the production of sound. This pressure wave leads to the vibrational motion of particles in the surrounding medium, whether it’s air, water, or a solid. The vibrating particles then transmit the sound further through the medium by moving nearby particles. Sound waves are detected by the human ear when vibrating air particles cause small parts within the ear to vibrate.
In several aspects, sound waves share similarities with light waves. Both types of waves have a specific source and can be dispersed or scattered using different methods. Unlike light waves, however, sound waves can only travel through a medium such as air, glass, or metal. This means that there is no sound in space!
TYPES OF SOUND WAVES
There are three kinds of sound waves exist. They are:
- Subsonic sound waves: Sound waves whose frequency is less than 20 Hz are called subsonic waves. This wave can be caused by the vibration of very large sensors. Waves produced by earthquakes are an example of a subsonic wave.
- Ultrasonic sound waves: Sound waves whose frequency is higher than 20000 Hz are called ultrasonic waves. The bat creates these waves on its face while flying. If there is an obstacle in front, this wave is reflected by that obstacle. Bats sense the location of obstacles by listening to reflected waves.
- Infrasonic sound waves: Low-frequency sound, which is also called infrasonic sound waves, pertains to sound waves with a frequency below the lower limit of what can be heard (around 20 Hz). As frequency decreases, our ability to hear diminishes, so the sound pressure needs to be relatively high for humans to detect infrasound. While the ear is the primary organ for perceiving low-frequency sound, excessive levels of infrasound vibrations can be felt in various parts of the body.
PROPAGATION OF SOUND
- Sound propagates through any medium (gaseous, liquid or solid) in the form of longitudinal waves and no displacement of the particles of the medium occurs during sound propagation.
- The elasticity of the medium is due to the fact that a compressed layer tends to expand again or an expanded layer tries to return to equilibrium by contracting again. So, sound cannot propagate without a medium and sound waves are elastic waves.
- For one complete vibration of a vibrating object, a condensation and rarefaction occurs in the inert medium. So, the wave produced by the combination of these two is a complete wave.
- The frequency of the sound wave is the same as the frequency of the vibrating source.
- It takes time for sound waves to propagate through any inert medium. So, it can be said that sound has specific velocity. Speed of sound is different in different media. Again, if the temperature of the medium is changed without changing the medium, the speed of sound also changes.
- In the case of words, there are properties such as reflection, refraction, interference, diffraction etc.
- Sound is longitudinal wave. So, there is no polarisation of sound.
SPEED OF SOUND
Sound takes some time to travel any distance, i.e. sound has definite speed. It is easily understood by comparing it with the speed of light. In many everyday occurrences light and sound originate simultaneously. Because the speed of light is so high (about 186,000 mi or 300,000 km per second), it reaches the eyes of a distant observer almost instantaneously. However, since the speed of sound is relatively low, it takes a little longer to reach the ear. The speed of sound in air at 0°C is about 332 m/s. This velocity increases as temperature increases, other physical conditions also affect the velocity of sound.
Through Material Medium
Scientist Newton showed theoretically that the speed of sound through medium,
c = √E/ρ ………..(1)
(where, ρ = density of the medium, E = coefficient of elasticity of the medium).
Through Gaseous Medium
c = √γp/ρ ………..(2)
For air at STP, γ = 1.4, p = 76 X 13.6 X 980 dyn/cm², ρ = 0.001293 gm/cm³.
So, c = 33117 cm/s = 331.2 m/s
Through Solid and Liquid Medium
c = √Y/ρ ………(3)
& c = √k/ρ ……….(4)
Where, Y = Young’s modulus, k = Bulk modulus, ρ = density of the liquid or solid.
SPEED OF SOUND IN DIFFERENT MEDIUM
| Medium | Speed of Sound (m/s) | Medium | Speed of Sound (m/s) |
|---|---|---|---|
Air (0°C) | 331 | Water (4°C) | 1436 |
Air (20°C) | 343 | Copper | 3970 |
Oxygen (0°C) | 317 | Distilled water (25°C) | 1496 |
Hydrogen (0°C) | 1286 | Steel | 4700 - 5200 |
Carbon dioxide (0°C) | 257 | Glass | 4000 - 5000 |
APPLICATION OF SOUND
Sound serves various purposes in everyday life and across different sectors. Within the medical field, ultrasound is utilized for both imaging and diagnosing medical conditions. SONAR technology is instrumental for navigation and exploration, particularly in underwater environments. Sound plays a pivotal role in facilitating verbal communication and the operation of telecommunication devices. In the realm of entertainment, it enriches experiences in music, movies, and gaming. Furthermore, sound is essential in engineering for structural analysis, such as identifying cracks through acoustic testing. In wildlife research, it contributes to the study of animal behaviour. Moreover, sound-based alarms and warning systems enhance safety in transportation and public alert systems.
CONCLUSION
The role of sound in our everyday lives is essential, as it allows for communication, music, and awareness of our surroundings. Sound moves through different mediums, including air, water, and solids, in the form of vibrations. Appreciating the significance of sound enhances our understanding of its presence in nature, technology, and human life.