The vertical distance of the peak of the wave from the equilibrium point (horizontal line running through the wave). It is half of the height of the wave from the trough to the peak.
Compression
The region where the particles are closely packed when describing a longitudinal wave
Diaphragm
A thin membrane in a microphone that detects sound by oscillating at the same frequency as the sound waves.
Eardrum
A thin layer of skin within the ear that detects sound by oscillating at the same frequency as the sound waves that reach it from the air in the ear canal.
Echo
Reflected waves, typically sound waves.
Echolocation
A method of emitting sound waves and then detecting their echoes to find prey and obstacles that must be avoided.
Equilibrium position
Where the particles in a medium would rest if there were no wave passing through it.
Frequency
The number of oscillations or waves per second. Frequency is measured in hertz, Hz.
Hertz (Hz)
The unit that is used to measure frequency. It is abbreviated to Hz.
Infrasound
Sounds that have a frequency lower than 20 hertz that is too low for humans to hear.
Larynx
The part of your throat that contains your vocal cords. It is also known as your voice box.
Longitudinal wave
A type of wave in which the particles in the medium are oscillating (vibrating) in the same direction as the direction that the wave is moving as it transfers energy.
Medium
The substance that a wave passes through.
Octave
A scale or separation of eight musical notes, where the frequency is doubled or halved.
Oscillation
Vibration about a particular point.
Oscilloscope
A device for displaying waveforms on a screen so that measurements can be made of them, such as their amplitude.
Peak
The highest point on the wave.
Pitch
How high or low a musical note is. Pitch is determined by the frequency of the sound wave.
Rarefaction
A region in a longitudinal wave where the particles in the medium are less widely spaced than they were before the wave began moving through the medium.
Rogue wave
An extremely tall wave that appears as if from nowhere on an otherwise normal sea. It is caused by constructive interference of waves.
SONAR
A device used by ships and submarines to find the depth of the sea and to detect things like shoals of fish, using sound waves. SONAR stands for SOund Navigation And Ranging.
Sound wave
A longitudinal wave that passes through solids, liquids and gases because of the particles vibrating at a frequency that can be detected by the ear and therefore heard.
Transducer
A device that shifts energy from one store to another as part of a signalling or communication system.
Transverse wave
A wave in which the oscillations are at right angles to the direction in which the wave is moving, and thus the direction of energy transfer.
Trough
The lowest point of a transverse wave. It is the furthest point from a peak.
Ultrasound
Sound waves that have a frequency higher than 20 kilohertz which is too high for humans to hear.
Wave
A regular oscillation passing through a medium. The wave transfers energy without transferring the medium itself.
Wavefront
A line drawn along a wave (when viewed from above) that joins points that all have the same peak. Wavefronts are at right angles to the direction of the movement of the wave.
Wavelength
The distance between two adjacent peaks on a wave. At a given wave speed, the longer the wavelength, the lower the frequency.