Compression waves travelling down a slinky are a basic illustration of such waves. By pushing and pulling the slinky horizontally, one may create a longitudinal wave. When these waves move through a medium, they cause compression and rarefaction. That is, adjacent portions of the medium are pushed together or pulled apart by the wave.
Longitudinal waves can be found in many things around us. A drum head produces longitudinal waves when it is beaten. Longitudinal waves also occur as part of the sound produced by some instruments, for example the violin. Even thunder is a form of longitudinal wave: it is our interpretation of this sound that creates the feeling of danger or not.
Longitudinal waves are responsible for the loudness of certain sounds and the sensitivity of hearing to high frequencies. Without these waves, music would be too quiet to hear and lightning would be like exploding fireworks!
The study of longitudinal waves is called "acoustics". Acoustic engineers use knowledge of how objects with different shapes and materials reflect sound to design products such as headphones and microphones. Scientists have also studied how animals such as whales and bats use sound waves to communicate over long distances without using wires or radio signals.
In physics, longitudinal waves are one type of wave. They require a force acting on the medium in the direction it moves.
Pressure waves are the name given to the longitudinal waves. These are the longitudinal waves. Longitudinal waves are referred to as "pressure waves." When compression and rarefaction occur, the propagation of longitudinal waves in a medium involves changes in pressure and volume of air. The term "pressure wave" is also used to describe other types of longitudinal waves such as those that occur in water or glass.
Longitudinal waves can be either surface waves or body waves. In surface waves, the wave moves along the surface of the medium; this type of wave is called a "surface wave". In body waves, the wave travels through the medium below its surface; this type of wave is called a "body wave".
The direction of travel for both surface waves and body waves is parallel to the direction of maximum stress in the medium. This means that if you were to draw a diagram of the path that these waves would take, they would all point in the same direction. Body waves always travel farther than surface waves because they can travel more deeply into the medium.
Surface waves can be divided up into three different types according to how they are generated: sea waves, wind waves, and rippling waves. Sea waves are the most common type of surface wave and they can be generated by several different factors. Wind waves are caused by winds blowing against the surface of the medium and they can be very large.
Because it needs pressure on the medium to propagate, this sort of wave is also known as a compressive wave. The peak and trough of a transverse wave correspond to compression and rarefaction in a longitudinal wave, respectively. When the particles in the medium through which the wave is passing are crushed, this is referred to as compression. If the particles are spread out, this is called expansion. A longitudinal wave is also called a tension wave because peaks and troughs on either side of the particle axis represent tension and compression along that axis.
A wave can be considered both transverse and longitudinal depending on the nature of its oscillations. For example, a sound wave is both transverse and longitudinal, but a surface wave such as a tsunami is only longitudinal.
Longitudinal waves are commonly found in ocean waves and underground as seismic waves. Seismic waves travel through Earth's solid material, causing small changes in density and therefore creating disturbances that can be felt by people living near their path. Ocean waves are made up of different types of longitudinal waves: sea waves are made up of water droplets suspended in air, while lake waves are made up of water droplets trapped in ice.
The frequency of a longitudinal wave is the number of times it crosses some fixed point per second. So, the frequency of ocean waves is usually expressed in hertz (Hz), with one Hz being one wave per second.