sineaalto

Sineaalto, also known as a sinusoid, is a smooth periodic oscillation whose instantaneous value follows a sine function over time. In mathematical terms, it can be written as y(t) = A sin(2π f t + φ), where A is the amplitude, f is the frequency, and φ is the phase. The wave is periodic with period T = 1/f, and the angular frequency ω = 2π f.

As a waveform, the sine wave is the simplest non-constant periodic signal. In Fourier analysis, a pure sine contains a single frequency component, while more complex waveforms can be decomposed into sums of sinusoids with different frequencies and amplitudes. A sine wave is infinitely differentiable and has no discontinuities, which makes it ideal for modeling and testing linear time-invariant systems.

Sine waves are generated in electronics and signal processing by oscillator circuits (RC, LC, crystal oscillators) or by digital synthesis using phase-accumulation or direct digital synthesis methods. They are used as reference signals, test tones, carriers in communication systems, and building blocks for audio synthesis and modulation schemes. In analysis, sine waves simplify the study of system response because of their consistent frequency content.

In Finnish terminology, siniaalto is the standard term for a sine wave; sineaalto is a less common spelling variant or loanword. See also sinusoid, waveform, Fourier analysis.