Sound

Sound is a fascinating phenomenon that lets us hear everything around us, from birds chirping to music playing. It happens when pressure changes move through materials like air, water, or solids. These changes are called mechanical waves, and they carry energy from one place to another.

Our ears can detect sounds with frequencies between 20 hertz and 20 kilohertz, which means we can hear a wide range of noises. Sound is very important in many parts of life. It lets us enjoy music, use spoken language to talk to each other, and even helps doctors look inside the body using special imaging techniques. Understanding sound is also a big part of many areas of science.

Definition

Sound is a type of wave that moves through materials like air, water, or solids. It is created when something vibrates, causing small changes in pressure that travel through the material. These changes can be heard by our ears, which pick up the vibrations and send them to the brain, allowing us to perceive sound.

In science, sound is often described as a disturbance that moves through a medium, changing how the particles in that material are pressed together and spread apart. This helps scientists understand how sound works in different situations.

Acoustics

Main article: Acoustics

Acoustics is the scientific study of sound and related waves, such as vibrations and ultrasound, in different materials like air, water, or solids. Scientists who study acoustics are called acousticians, and those who apply this knowledge in engineering are known as acoustical engineers. Audio engineers focus on recording and manipulating sound.

Acoustics has many practical uses in everyday life. It includes areas like architectural acoustics, which helps design quiet and pleasant spaces, as well as musical acoustics, which studies the science behind music. Other fields involve controlling noise, understanding how animals communicate with sound, and exploring sound under water.

Physics

Sound travels as a mechanical wave through materials like water, crystals, or air. It is created by a source, such as a vibrating loudspeaker diaphragm, which moves the surrounding material and creates a wave of pressure changes. These waves move away from the source at the speed of sound, changing the pressure, speed, and position of particles in the material as they pass by.

Sound can only travel through materials that have particles to move—like solids, liquids, or gases. It cannot travel through a vacuum, where there are no particles. The speed of sound changes depending on the material it travels through and conditions like temperature. In air at room temperature, sound travels at about 343 meters per second. In water, it moves faster, and in solids like steel, it moves even faster. Sound waves can also change direction or get weaker depending on the material they move through.

Perception

Main article: Psychoacoustics

In physiology and psychology, the term sound refers to what we feel when our ears pick up vibrations in the air. This is different from the scientific meaning of sound, which looks at how these vibrations travel. The study of how we hear and understand sounds is called psychoacoustics, a part of the larger field of psychophysics.

Humans can hear sounds that vibrate between about 20 times a second (Hz) and 20,000 times a second (kHz). As we get older, we usually lose the ability to hear the very high sounds. Some animals, like dogs, can hear even higher sounds than we can. Sound helps animals detect danger, find food, navigate, and talk to each other. On Earth, many things create sounds, like wind, rain, or animals communicating. Humans have also created tools like music, telephones, and radios to make, send, and receive sounds.

Noise is simply unwanted sound. In science, noise can block the sounds we want to hear, but for our ears, noise can help us figure out where a sound is coming from. The word soundscape describes all the sounds around us in a place, whether we can hear them or not.

Frequency

See also: Audio frequency

Ultrasound is sound with frequencies higher than 20,000 Hz, which humans cannot hear. It is used in medical tools to help doctors see inside the body.

Infrasound is sound with frequencies lower than 20 Hz. Humans can feel these sounds as quick pulses. Animals like whales and elephants can hear infrasound and use it to talk to each other. Infrasound can also help scientists know when volcanoes are about to erupt and is sometimes used in music.

See also: Perception of infrasound