Onset refers to the beginning of a
musical note
In music, a note is the representation of a musical sound.
Notes can represent the pitch and duration of a sound in musical notation. A note can also represent a pitch class.
Notes are the building blocks of much written music: discretizatio ...
or other sound. It is related to (but different from) the concept of a
transient
ECHELON, originally a secret government code name, is a surveillance program ( signals intelligence/SIGINT collection and analysis network) operated by the five signatory states to the UKUSA Security Agreement:Given the 5 dialects that ...
: all musical notes have an onset, but do not necessarily include an initial transient.
Onset detection
In
signal processing
Signal processing is an electrical engineering subfield that focuses on analyzing, modifying and synthesizing '' signals'', such as sound, images, and scientific measurements. Signal processing techniques are used to optimize transmissions, ...
, onset detection is an active research area. For example, the
MIREX annual competition features a
Audio Onset Detection contest
Approaches to onset detection can operate in the
time domain
Time domain refers to the analysis of mathematical functions, physical signals or time series of economic or environmental data, with respect to time. In the time domain, the signal or function's value is known for all real numbers, for the ...
,
frequency domain
In physics, electronics, control systems engineering, and statistics, the frequency domain refers to the analysis of mathematical functions or signals with respect to frequency, rather than time. Put simply, a time-domain graph shows how a ...
,
phase domain, or
complex domain
In mathematics, a complex number is an element of a number system that extends the real numbers with a specific element denoted , called the imaginary unit and satisfying the equation i^= -1; every complex number can be expressed in the form a ...
, and include looking for:
* Increases in spectral energy
* Changes in spectral energy distribution (
spectral flux) or
phase
* Changes in detected pitch - e.g. using a
polyphonic
Polyphony ( ) is a type of musical texture consisting of two or more simultaneous lines of independent melody, as opposed to a musical texture with just one voice, monophony, or a texture with one dominant melodic voice accompanied by chords, h ...
pitch detection algorithm
* Spectral patterns recognisable by
machine learning
Machine learning (ML) is a field of inquiry devoted to understanding and building methods that 'learn', that is, methods that leverage data to improve performance on some set of tasks. It is seen as a part of artificial intelligence.
Machine ...
techniques such as
neural network
A neural network is a network or neural circuit, circuit of biological neurons, or, in a modern sense, an artificial neural network, composed of artificial neurons or nodes. Thus, a neural network is either a biological neural network, made up ...
s.
Simpler techniques such as detecting increases in time-domain amplitude can typically lead to an unsatisfactorily high amount of
false positive
A false positive is an error in binary classification in which a test result incorrectly indicates the presence of a condition (such as a disease when the disease is not present), while a false negative is the opposite error, where the test resul ...
s or
false negatives.
The aim is often to judge onsets similarly to how a human would: so
psychoacoustically-motivated strategies may be employed. Sometimes the onset detector can be restricted to a particular domain (depending on intended application), for example being targeted at detecting percussive onsets. With a narrower focus, it can be more straightforward to obtain reliable detection.
See also
*
ADSR envelope ADSR may refer to:
*ADSR envelope (attack decay sustain release), a common type of music envelope
* Accelerator-driven sub-critical reactor, a nuclear reactor using a particle accelerator to generate a fission reaction in a sub-critical assembly of ...
*
Prefix (acoustics)
References
* Bello, J.P., Daudet, L., Abdallah, S., Duxbury, C., Davies, M., Sandler, M.B. (2005
"A Tutorial on Onset Detection in Music Signals" IEEE Transactions on Speech and Audio Processing 13(5), pp 1035–1047
* Bello, J.P, Duxbury, C., Davies, M., Sandler, M. (2004)
"On the use of phase and energy for musical onset detection in the complex domain" ''IEEE Signal Processing Letters''
* Collins, N. (2005
"A Comparison of Sound Onset Detection Algorithms with Emphasis on Psychoacoustically Motivated Detection Functions" Proceedings of AES118 Convention
Psychoacoustics
Synthesizers
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