Acoustic terms

Sound timbre

Overtones, Harmonics - Every sound consists, in fact, of a series of harmonics sounded together. Two sounds of the same volume and pitch, originating from different instruments, sound different since the relative volumes of their overtones (harmonics higher than the basic frequency) are different. If, in a particular sound the higher overtones are more intense, for example, the sound will be sharp and even discordant. A sound whose lower overtones are more intense, will be slightly muffled.

Resonance - Every body making a sound has its own resonance frequency. This frequency is the regularity in which an outside sound provokes a sonic reaction on its behalf. The phenomenon of resonance is probably familiar to all of you: windows trembling as an airplane makes a supersonic boom, glass that hum with a certain note of the piano, etc. All of those bodies simply react to sounds in their own resonance frequency.

Sound components

Frequency - The number of a body's vibration per time unit forms frequency of the sound it makes. The higher the frequency is (that is, the bigger number of vibrations), the higher the sound would be. The measurement unit is Hertz (Hz). 1 Hz = one vibration per second.

Wavelength - The wavelength is the distance between too similar points on the wave - this parameter is frequency's opposite, and in fact its inversion. The higher the frequency - the shorter the wavelength.

Waveform - sets a sound's timbre. Since every natural sound consists of several sound waves sounded together, they make a complex wave form. If the wave form is cyclic, the sound has a definite pitch. An irregular sound form is noise.

Amplitude - Amplitude sets a sound's volume. It is the maximal distance from point of equilibrium in the regular motion on the generated sound.

The sound description

Except for the timbre of a musical sound, there is another component, assisting its identification. And that is the graph of its changing along the time axis: the envelope.

This sound's appearance (envelope) consists of four main phases:

1) Attack - sound volume leaps from zero to its maximum volume.

2) Decay - volume drop from peak.

3) Sustain - a certain time in which sound remains at a certain volume, almost unchanged.

4) Release - sound drops to zero volume.