Audio analysis refers to the extraction of information and meaning from audio signals for analysis,
classification
Classification is the activity of assigning objects to some pre-existing classes or categories. This is distinct from the task of establishing the classes themselves (for example through cluster analysis). Examples include diagnostic tests, identif ...
, storage, retrieval,
synthesis
Synthesis or synthesize may refer to:
Science Chemistry and biochemistry
*Chemical synthesis, the execution of chemical reactions to form a more complex molecule from chemical precursors
**Organic synthesis, the chemical synthesis of organi ...
, etc. The observation mediums and interpretation methods vary, as audio analysis can refer to the human ear and how people interpret the audible sound source, or it could refer to using technology such as an
audio analyzer to evaluate other qualities of a sound source such as
amplitude
The amplitude of a periodic variable is a measure of its change in a single period (such as time or spatial period). The amplitude of a non-periodic signal is its magnitude compared with a reference value. There are various definitions of am ...
,
distortion
In signal processing, distortion is the alteration of the original shape (or other characteristic) of a signal. In communications and electronics it means the alteration of the waveform of an information-bearing signal, such as an audio signal ...
,
frequency response
In signal processing and electronics, the frequency response of a system is the quantitative measure of the magnitude and Phase (waves), phase of the output as a function of input frequency. The frequency response is widely used in the design and ...
. Once an audio source's information has been observed, the information revealed can then be processed for the logical, emotional, descriptive, or otherwise relevant interpretation by the user.
Natural Analysis
The most prevalent form of audio analysis is derived from the sense of
hearing
Hearing, or auditory perception, is the ability to perceive sounds through an organ, such as an ear, by detecting vibrations as periodic changes in the pressure of a surrounding medium. The academic field concerned with hearing is auditory sci ...
. A type of sensory perception that occurs in much of the planet's fauna, audio analysis is a fundamental process of many living beings. Sounds made by the surrounding environment or other living beings provides input to the hearing mechanism, for which the listener's brain can interpret the sound and how it should respond. Examples of functions include
speech
Speech is the use of the human voice as a medium for language. Spoken language combines vowel and consonant sounds to form units of meaning like words, which belong to a language's lexicon. There are many different intentional speech acts, suc ...
,
startle response
In animals, including humans, the startle response is a largely unconscious defensive response to sudden or threatening Stimulus (physiology), stimuli, such as sudden noise or sharp movement, and is associated with negative Affect (psychology), af ...
,
music
Music is the arrangement of sound to create some combination of Musical form, form, harmony, melody, rhythm, or otherwise Musical expression, expressive content. Music is generally agreed to be a cultural universal that is present in all hum ...
listening, and more.
An inherent ability of humans, hearing is fundamental in communication across the globe, and the process of assigning meaning and value to speech is a complex but necessary function of the human body. The study of the auditory system has been greatly centered using mathematics and the analysis of sinusoidal vibrations and sounds. The
Fourier transform
In mathematics, the Fourier transform (FT) is an integral transform that takes a function as input then outputs another function that describes the extent to which various frequencies are present in the original function. The output of the tr ...
has been an essential theorem in understanding how the human ear processes moving air and turns it into the audible frequency range, about 20 to 20,000 Hz. The ear is able to take one complex waveform and process it into varying frequency ranges thanks to differences in the structures of the ear canal that are tuned to specific frequency ranges. The initial sensory input is then analyzed further up in the neurological system where the perception of sound takes place.
The auditory system also works in tandem with the neural system so that the listener is capable of spatially locating the direction from which a sound source originated. This is known as the
Haas or Precedence effect and is possible due to the nature of having two ears, or auditory receptors. The difference in time it takes for a sound to reach both ears provides the necessary information for the brain to calculate the spatial positioning of the source.
Signal Analysis
Audio signals can be analyzed in several different ways, depending on the kind of information desired from the signal.
Types of signal analysis include:
*
Level and gain
*
Frequency domain
In mathematics, physics, electronics, control systems engineering, and statistics, the frequency domain refers to the analysis of mathematical functions or signals with respect to frequency (and possibly phase), rather than time, as in time ser ...
analysis
*
Frequency response
In signal processing and electronics, the frequency response of a system is the quantitative measure of the magnitude and Phase (waves), phase of the output as a function of input frequency. The frequency response is widely used in the design and ...
*
Total Harmonic Distortion plus Noise (THD+N)
*
Phase
Phase or phases may refer to:
Science
*State of matter, or phase, one of the distinct forms in which matter can exist
*Phase (matter), a region of space throughout which all physical properties are essentially uniform
*Phase space, a mathematica ...
*
Crosstalk
In electronics, crosstalk (XT) is a phenomenon by which a signal transmitted on one circuit or channel of a transmission system creates an undesired effect in another circuit or channel. Crosstalk is usually caused by undesired capacitive, ...
*
Intermodulation distortion
Intermodulation (IM) or intermodulation distortion (IMD) is the amplitude modulation of signals containing two or more different frequencies, caused by nonlinearities or time variance in a system. The intermodulation between frequency compo ...
(IMD)
*Stereo and Surround

Hardware analyzers have been the primary means of signal analysis since the invention of the first audio analyzer, made by
Hewlett-Packard
The Hewlett-Packard Company, commonly shortened to Hewlett-Packard ( ) or HP, was an American multinational information technology company. It was founded by Bill Hewlett and David Packard in 1939 in a one-car garage in Palo Alto, California ...
, the
HP200A. Hardware analyzers are typically used in engineering, testing, and manufacturing of professional and consumer grade products. As computer technology progressed, integrated software found its way into these hardware systems, and later there would be audio analysis tools that did not require any hardware components save for the computer running the software. Software audio analyzers are regularly used in various stages of music production, such as live audio, mixing, and mastering. These products tend to employ
Fast Fourier Transform (FFT) algorithms and processing to provide a visual representation of the signal being analyzed. Display and information types include frequency spectrum,
stereo field
Stereophonic sound, commonly shortened to stereo, is a method of sound reproduction that recreates a multi-directional, 3-dimensional audible perspective. This is usually achieved by using two independent audio channels through a configurat ...
,
surround field,
spectrogram
A spectrogram is a visual representation of the spectrum of frequencies of a signal as it varies with time.
When applied to an audio signal, spectrograms are sometimes called sonographs, voiceprints, or voicegrams. When the data are represen ...
, and more.
See also
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References
{{DEFAULTSORT:Audio Analysis
Audio engineering