Sound
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Vibrations that travel through air or matter
Sound is a type of energy that we can hear. It is produced when an object vibrates, causing the air or another material around it to move. These movements travel as waves through the air or other substances until they reach our ears. For example, when a drum is hit, its surface vibrates and makes the air vibrate too. The ear receives these vibrations and the brain understands them as sound.
Sound needs a material to travel through, such as air, water, or a solid object. These materials are called mediums. Sound cannot travel through a vacuum, because there are no particles to carry the vibrations. The speed of sound changes depending on the medium. It travels fastest through solids, slower through liquids, and slowest through gases like air. For instance, sound travels faster through metal than through air.
Sound moves in waves. A sound wave has two main parts: compression and rarefaction. Compression is where the air particles are close together, and rarefaction is where they are spread out. These waves can be described by their frequency and amplitude. Frequency is how many waves pass a point in one second and affects the pitch—how high or low a sound is. Amplitude measures the size of the vibration and affects the loudness of the sound.
Humans can usually hear sounds with frequencies between about 20 and 20,000 hertz (Hz). Sounds higher than this range are called ultrasound, and sounds lower are called infrasound. Some animals, like bats and dolphins, can hear ultrasound and use it for finding objects or hunting. This process is called echolocation.
The ear is the organ that detects sound. The outer ear collects sound waves and sends them through the ear canal to the eardrum, which vibrates. These vibrations move through tiny bones in the middle ear and then to the inner ear, where they are turned into signals that the brain can understand as sound. People can use devices called microphones to record sound or speakers to play it back.
Sound has many uses in daily life. People use speech and music to communicate and express themselves. Scientists and doctors use sound waves in tools such as ultrasound machines to study the inside of the human body. Understanding sound helps in designing buildings, musical instruments, and audio equipment that work well with how sound travels and behaves.
Sound needs a material to travel through, such as air, water, or a solid object. These materials are called mediums. Sound cannot travel through a vacuum, because there are no particles to carry the vibrations. The speed of sound changes depending on the medium. It travels fastest through solids, slower through liquids, and slowest through gases like air. For instance, sound travels faster through metal than through air.
Sound moves in waves. A sound wave has two main parts: compression and rarefaction. Compression is where the air particles are close together, and rarefaction is where they are spread out. These waves can be described by their frequency and amplitude. Frequency is how many waves pass a point in one second and affects the pitch—how high or low a sound is. Amplitude measures the size of the vibration and affects the loudness of the sound.
Humans can usually hear sounds with frequencies between about 20 and 20,000 hertz (Hz). Sounds higher than this range are called ultrasound, and sounds lower are called infrasound. Some animals, like bats and dolphins, can hear ultrasound and use it for finding objects or hunting. This process is called echolocation.
The ear is the organ that detects sound. The outer ear collects sound waves and sends them through the ear canal to the eardrum, which vibrates. These vibrations move through tiny bones in the middle ear and then to the inner ear, where they are turned into signals that the brain can understand as sound. People can use devices called microphones to record sound or speakers to play it back.
Sound has many uses in daily life. People use speech and music to communicate and express themselves. Scientists and doctors use sound waves in tools such as ultrasound machines to study the inside of the human body. Understanding sound helps in designing buildings, musical instruments, and audio equipment that work well with how sound travels and behaves.
What We Can Learn
- Sound is made by vibrations that travel through materials.
- It moves as waves of compression and rarefaction.
- Pitch and loudness depend on frequency and amplitude.
- The ear and brain work together to detect and understand sound.
