The sine wave or sinusoid is a mathematical function that describes a smooth repetitive oscillation. It occurs often in pure and applied mathematics, as well as physics, engineering, signal processing and many other fields. Its most basic form as a function of time (t) is:
y(t)=A ⋅ \sin(\omegat+\phi)
The sine wave is important in physics because it retains its waveshape when added to another sine wave of the same frequency and arbitrary phase. It is the only periodic waveform that has this property. This property leads to its importance in Fourier analysis and makes it acoustically unique.
In general, the function may also have:
which looks like this:
y(x,t)=A ⋅ \sin(\omegat-kx+\phi)+D.
The wavenumber is related to the angular frequency by:.
This equation gives a sine wave for a single dimension, thus the generalized equation given above gives the amplitude of the wave at a position x at time t along a single line.This could, for example, be considered the value of a wave along a wire.
In two or three spatial dimensions, the same equation describes a travelling plane wave if position x and wavenumber k are interpreted as vectors, and their product as a dot product. For more complex waves such as the height of a water wave in a pond after a stone has been dropped in, more complex equations are needed.
A cosine wave is said to be "sinusoidal", because
The human ear can recognize single sine waves as sounding clear because sine waves are representations of a single frequency with no harmonics; some sounds that approximate a pure sine wave are whistling, a crystal glass set to vibrate by running a wet finger around its rim, and the sound made by a tuning fork.
See main article: Fourier analysis.
In 1822, Joseph Fourier, a French mathematician, discovered that sinusoidal waves can be used as simple building blocks to describe and approximate any periodic waveform including square waves. Fourier used it as an analytical tool in the study of waves and heat flow. It is frequently used in signal processing and the statistical analysis of time series.
When two waves having the same amplitude and frequency superpose each other then a stationary wave pattern is created that is known as a stationary wave... Suppose a wave is of type y(t)=Asin(ωt-kx) then reflected wave would be of type... y(t)= -Asin(ωt+kx) so Asin(ωt-kx)-Asin(ωt+kx) = -2A sinkx cosωt which is a stationary wave equation (ref Rushi vyas textbook)