Spectral modeling synthesis (SMS) is an
acoustic modeling approach for speech and other signals.
SMS considers
sounds as a combination of
harmonic
A harmonic is a wave with a frequency that is a positive integer multiple of the ''fundamental frequency'', the frequency of the original periodic signal, such as a sinusoidal wave. The original signal is also called the ''1st harmonic'', the ...
content and
noise
Noise is unwanted sound considered unpleasant, loud or disruptive to hearing. From a physics standpoint, there is no distinction between noise and desired sound, as both are vibrations through a medium, such as air or water. The difference arise ...
content. Harmonic components are identified based on peaks in the
frequency spectrum of the signal, normally as found by the
short-time Fourier transform. The signal that remains following removal of the spectral components, sometimes referred to as the residual, is then modeled as
white noise
In signal processing, white noise is a random signal having equal intensity at different frequencies, giving it a constant power spectral density. The term is used, with this or similar meanings, in many scientific and technical disciplines, ...
passed through a time-varying filter. The output of the model, then, are the frequencies and levels of the detected harmonic components and the
coefficients of the time-varying filter.
Intuitively, the model can be applied to many types of audio signals. Speech signals, for example, include slowly changing harmonic sounds caused by vibration of the
vocal cords
In humans, vocal cords, also known as vocal folds or voice reeds, are folds of throat tissues that are key in creating sounds through vocalization. The size of vocal cords affects the pitch of voice. Open when breathing and vibrating for speech ...
plus wideband, noise-like sounds caused by the lips and mouth. Musical instruments also produce sounds containing both harmonic components and percussive, noise-like sounds when the notes are struck or changed.
See also
*
Speech coding
*
CELP
*
Source-filter model of speech production
*
FM synthesis
*
Sound synthesis
SPEAR - Sinusoidal Partial Editing Analysis and Resynthesis
References
*
*
*
*
*
Speech recognition
{{science-software-stub