Sound and waves

Sound is a fascinating topic that we encounter in our daily lives. The chirping of birds in the morning, the music we listen to, or just the simple act of talking are all examples of sound waves. This explanation will cover the basics of sound and waves, help you understand how they work, and explain their properties.

What is sound?

Sound is a type of energy that is produced when an object vibrates. These vibrations cause the air molecules around the object to move, creating sound waves. Our ears pick up these waves, and our brain interprets them as various sounds.

Introduction to waves

Waves are disturbances that transfer energy from one place to another. They are everywhere in our natural world and can be found in the ocean, in light, and of course in sound.

Types of waves

There are two main types of waves:

• Transverse waves: In these waves, the disturbance moves perpendicular to the direction of the wave. A typical example of this is waves on water.
• Longitudinal waves: In these waves, the disturbance moves in the direction of the wave. Sound waves are a type of longitudinal waves.

How sound waves work

Sound waves are created when an object vibrates. For example, when you strum a guitar string, it vibrates and creates a series of compressions and rarefactions in the air around it. These areas of high and low pressure travel through the air as longitudinal waves.

This diagram shows the series of compressions (closed circles) and rarefactions (dispersed circles) that create a sound wave.

Characteristics of sound waves

Let's explore some of the important properties of sound waves:

Frequency

Frequency tells us how many waves pass a point in one second. It is measured in Hertz (Hz). Higher frequency means higher pitch, and lower frequency means lower pitch. For example, the frequency of a dog whistle is higher than what humans can hear.

Wavelength

The distance between two successive compressions or rarefactions is called wavelength. It is usually measured in metres.

In this wave, the distance between the start of the wave and where it repeats (marked in red) is the wavelength.

Dimensions

The amplitude is the height of the wave above its rest position. It is related to the volume of the sound: the higher the amplitude, the louder the sound.

Speed of sound

Sound travels at different speeds depending on the medium (such as air, water or steel). In dry air at 20 degrees Celsius, the speed of sound is about 343 meters per second. The speed is faster in water and even faster in solids.

Noise and music

Noise is a random sound that has no definite tone and is unpleasant to the ear. Music is a pleasant sound that has a definite tone and pattern.

How do we hear sound?

Our ears are amazing organs designed to capture sound waves and help us hear. Here's a basic overview of how our hearing works:

1. Sound waves enter our outer ear and travel through the ear canal to the eardrum.
2. The eardrum vibrates in response to sound waves.
3. These vibrations reach three tiny bones located in the middle ear called the hammer, anvil, and stirrup.
4. These vibrations are then transmitted to the cochlea, a spiral-shaped organ filled with fluid in the inner ear.
5. Tiny hair cells inside the cochlea move in response to the vibrations and convert them into electrical signals.
6. Electrical signals are sent through the auditory nerve to the brain, where they are interpreted as sound.

Applications of sound

There are many applications of sound in our daily life:

• Communication: We use sound to communicate through conversations, phone etc.
• Music: Sound allows us to enjoy and perform music, providing entertainment and cultural enrichment.
• Sonar: Ships and submarines use sonar (sound navigation and ranging) to determine the distance between underwater objects.
• Medical imaging: Ultrasound uses high-frequency sound waves to make images of the inside of the body.

Representing sound waves visually

Sound waves can also be observed using oscilloscopes which present sound waves as waveforms. Here is an example of how sound waves may appear:

In this display, the blue line represents the sound's waveform, showing its amplitude over time.

Conclusion

Understanding sound and waves provides insight into how the world works. Sound is more than just noise; it is an important part of communication, art, technology and science. By studying the various properties of sound waves, such as frequency, wavelength and amplitude, you understand the rich and complex nature of sound. This knowledge forms a strong foundation for beginning more advanced studies in physics.

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