All sounds in nature are fundamentally constructed of sine waves. More complex sounds simply contain more oscillations at different frequencies, stacked one upon another. Higher-frequency, oscillations which are tonally related to the fundamental frequency (the base note or tone) are known as harmonics.
For a single-frequency sound wave, the rate at which it does this is regular and continuous, taking the shape of a sine wave. Thus, the graph of a sound wave is a simple sine wave only if the sound has only one frequency component in it – that is, just one pitch.
Based on a sinusoidal model, an analysis/synthesis technique is developed that characterizes audio signals, such as speech and music, in terms of the amplitudes, frequencies, and phases of the component sine waves.
A sine wave is the simplest of all waveforms and contains only a single fundamental frequency and no harmonics or overtones.
The oscillation of light waves and sound waves (and many other waves) can be described with sinusoidal functions in time (frequency) and in space (wavenumber). Moreover, oscillation of monochromatic waves is perfectly described by a single sinusoidal (single frequency and wavenumber) function.
A sine wave is a simple periodic sound. Musical instruments or the voice produce complex periodic sounds. They have a spectrum consisting of a series of harmonics. Each harmonic is a sine wave that has a frequency that is an integer multiple of the fundamental frequency.
A sine wave has a single frequency component: a fundamental harmonic with absolutely no overtones. If dissected into harmonic components, white noise, on the other hand, contains every frequency, amplitude, and phase relation of a sine wave throughout the audible spectrum.
The sound wave from the flute is very smooth and looks like a sine wave from a mathematics textbook. A flute has a strong fundamental frequency of 262 Hz and practically no other harmonics or overtones. A musician might describe a flute as having a very pure tone.
All string and wind instruments produce pure sine waves. The thing is, usually they produce more than one of them at a time, at multiples of the root.
This combination of many sines waves that are all integer multiples of the fundamental is what gives a piano its distinctive sound. If just the fundamental sine wave vibrated when you pressed a key, it would sound like a cheap alarm clock.
Electrical power can be graphically depicted as a sine wave whereby the electrical signal alternates from +120 volts to -120 volts at a rate of 60 times per second (60 Hz).
The frequency of a sound can be calculated by dividing the rate of the compressions and rarefactions by the length of a soundwave. An oscilloscope is an electronic device that is often used to measure and visualize a sound's frequency. Spectrum represents how many different frequencies a sound produces.
Longitudinal waves
A longitudinal wave is one where all the particles of the medium (such as gas, liquid or solid) vibrate in the same direction as the wave. Sound waves are longitudinal waves. When longitudinal waves travel through any given medium, they also include compressions and rarefactions.
DEFINITION: A sine wave sounds like it looks: smooth and clean. It is sound at its most basic. The sound of a sine wave is only made up of one thing, something known as the fundamental. No partials to be seen!
Sine waves are one of the most common forms of electrical or electronic waveform. Sine waves are the waveform that is seen when displaying electrical supply or mains waveforms, most RF or radio frequency waveforms, as well as some audio test signals.
The variable could be audible sound for example. A single pure note is a sine wave, although it would sound a very plain and flat note indeed with none of the harmonics we normally hear in nature. A straightforward oscillating or alternating current or voltage within a wire can also be represented by a sine wave.
AC (alternating current) means that the voltage swings positive and negative like this sine wave. Guitar signals are AC voltages, just a wee bit more complex than the simple sine wave above.
In general, the fundamental frequency of a guitar string is 80 Hz, but it can reach 1200 Hz. Every note has harmonics, which correspond to energy in different ways. At 440 Hz, for example, an harmonic of note A would be the same as 880 Hz, 1680 Hz, and so on.
The sound of the flute is a little like a sine wave (a very pure vibration) when played softly, but successively less like it as it is played louder. To make a repeated or periodic wave that is not a simple sine wave, one can add sine waves from the harmonic series.
While the fundamental is usually heard most prominently, overtones are actually present in any pitch except a true sine wave.
One representative example of something that creates a pure sound, or only a fundamental tone with no harmonics, is a tuning fork.
If the amplitude of the sine waves decreases with a curve of about -6 dB per octave when their frequencies rise, the noise sounds much warmer. This is called pink noise. Pink noise contains equal energy per octave (or per 1/3 octave).
Pink noise is a category of sounds that contains all the frequencies that a human ear can hear, or 20 Hz to 20,000 Hz, says Iris Langman, MSPA, a clinical audiologist at the UW Medicine Northwest Outpatient Medical Center. Although pink noise contains all of these frequencies, we don't hear all of them equally.