In
signal processing
Signal processing is an electrical engineering subfield that focuses on analyzing, modifying and synthesizing ''signals'', such as audio signal processing, sound, image processing, images, and scientific measurements. Signal processing techniq ...
, the high frequency content measure is a simple measure, taken across a signal
spectrum
A spectrum (plural ''spectra'' or ''spectrums'') is a condition that is not limited to a specific set of values but can vary, without gaps, across a continuum. The word was first used scientifically in optics to describe the rainbow of colors i ...
(usually a
STFT
The short-time Fourier transform (STFT), is a Fourier-related transform used to determine the sinusoidal frequency and phase content of local sections of a signal as it changes over time. In practice, the procedure for computing STFTs is to divi ...
spectrum), that can be used to characterize the amount of high-frequency content in the signal. The magnitudes of the spectral bins are added together, but multiplying each magnitude by the bin "position" (proportional to the frequency). Thus if ''X''(''k'') is a discrete spectrum with ''N'' unique points, its high frequency content measure is:
:
In contrast to perceptual measures, this is not based on any evidence about its relevance to
human 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 ...
. Despite that, it can be useful for some applications, such as
onset detection
Onset refers to the beginning of a musical note or other sound. It is related to (but different from) the concept of a transient: all musical notes have an onset, but do not necessarily include an initial transient.
Onset detection
In signal pro ...
.
The measure has close similarities to the
spectral centroid The spectral centroid is a measure used in digital signal processing to characterise a spectrum. It indicates where the center of mass of the spectrum is located. Perceptually, it has a robust connection with the impression of brightness of a sou ...
measure, being essentially the same calculation but without normalization according to overall magnitude.
References
* P. Brossier, J. P. Bello and M. D. Plumbley.
Real-time temporal segmentation of note objects in music signals', in Proceedings of the International Computer Music Conference (ICMC 2004), Miami, Florida, USA, November 1–6, 2004.
* Masri, P. (1996). ''Computer modeling of Sound for Transformation and Synthesis of Musical Signal.'' PhD dissertation, University of Bristol.
Digital signal processing
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