Sound chipA sound chip is an integrated circuit (chip) designed to produce audio signals through digital, analog or mixed-mode electronics. Sound chips are typically fabricated on metal–oxide–semiconductor (MOS) mixed-signal chips that process audio signals (analog and digital signals, for both analog and digital data). They normally contain audio components such as oscillators, envelope controllers, samplers, filters, amplifiers, and envelope generators. A number of sound synthesis methods for electronically producing sound were devised during the late 20th century.
Low-frequency oscillationLow-frequency oscillation (LFO) is an electronic frequency that is usually below 20 Hz and creates a rhythmic pulse or sweep. This is used to modulate musical equipment such as synthesizers to create audio effects such as vibrato, tremolo and phasing. Low-frequency oscillation was introduced with modular synthesizers of the 1960s, such as the Moog synthesizer. Often the LFO effect was accidental, as there were myriad configurations that could be "patched" by the synth operator.
Acoustic waveAcoustic waves are a type of energy propagation through a medium by means of adiabatic loading and unloading. Important quantities for describing acoustic waves are acoustic pressure, particle velocity, particle displacement and acoustic intensity. Acoustic waves travel with a characteristic acoustic velocity that depends on the medium they're passing through. Some examples of acoustic waves are audible sound from a speaker (waves traveling through air at the speed of sound), seismic waves (ground vibrations traveling through the earth), or ultrasound used for medical imaging (waves traveling through the body).
Reverb effectA reverb effect, or reverb, is an audio effect applied to a sound signal to simulate reverberation. It may be created through physical means, such as echo chambers, or electronically through audio signal processing. The American producer Bill Putnam is credited for the first artistic use of artificial reverb in music, on the 1947 song "Peg o' My Heart" by the Harmonicats. Spring reverb, created with a series of mounted springs, is popular in surf music and dub reggae.
Audio time stretching and pitch scalingTime stretching is the process of changing the speed or duration of an audio signal without affecting its pitch. Pitch scaling is the opposite: the process of changing the pitch without affecting the speed. Pitch shift is pitch scaling implemented in an effects unit and intended for live performance. Pitch control is a simpler process which affects pitch and speed simultaneously by slowing down or speeding up a recording. These processes are often used to match the pitches and tempos of two pre-recorded clips for mixing when the clips cannot be reperformed or resampled.
Audio filterAn audio filter is a frequency dependent circuit, working in the audio frequency range, 0 Hz to 20 kHz. Audio filters can amplify (boost), pass or attenuate (cut) some frequency ranges. Many types of filters exist for different audio applications including hi-fi stereo systems, musical synthesizers, effects units, sound reinforcement systems, instrument amplifiers and virtual reality systems. Low-pass Low-pass filters pass through frequencies below their cutoff frequencies, and progressively attenuates frequencies above the cutoff frequency.
Physical modelling synthesisPhysical modelling synthesis refers to sound synthesis methods in which the waveform of the sound to be generated is computed using a mathematical model, a set of equations and algorithms to simulate a physical source of sound, usually a musical instrument. Modelling attempts to replicate laws of physics that govern sound production, and will typically have several parameters, some of which are constants that describe the physical materials and dimensions of the instrument, while others are time-dependent functions describing the player's interaction with the instrument, such as plucking a string, or covering toneholes.
LoudnessIn acoustics, loudness is the subjective perception of sound pressure. More formally, it is defined as the "attribute of auditory sensation in terms of which sounds can be ordered on a scale extending from quiet to loud". The relation of physical attributes of sound to perceived loudness consists of physical, physiological and psychological components. The study of apparent loudness is included in the topic of psychoacoustics and employs methods of psychophysics.
