Glover, John C.
Sinusoids, noise and transients: spectral
analysis, feature detection and real-time
transformations of audio signals for musical
PhD thesis, National University of Ireland Maynooth.
This thesis examines the possibilities for real-time transformations of musical audio
signals using sinusoidal models. Four open-source software libraries were developed
with the goal of providing real-time spectral synthesis by analysis tools
for composers, musicians, researchers and audio signal processing developers. The
first of these, called Simpl, provides a consistent API for interacting with established
sinusoidal modelling systems from the literature, and integrates seamlessly with a
powerful suite of libraries for scientific computing.
Sinusoidal models have been used to transform slowly-varying quasi-harmonic
signals with much success, but they have well-documented weaknesses in dealing
with transient signal regions. This problem is significant, as in monophonic musical
sounds, transient locations often correspond with the attack section of notes and
this region plays a large part in our perception of timbre. However in order to
improve the synthesis of note attack transients, these regions must first be accurately
identified. The first step in this attack transient identification process is generally
musical note onset detection. Novel approaches to real-time note onset detection
were developed as part of this research and are included in the Modal open-source
software library. Modal also includes a set of reference samples that were used to
evaluate the performance of the onset detection systems, with the novel methods
being shown to perform better than leading solutions from the literature.
The onset detection process was then combined with cues taken from the amplitude
envelope and the spectral centroid to produce a novel method for segmenting
musical tones into attack, sustain and release regions in real-time. The real-time segmentation
method was shown to compare favourably with a leading non-real-time
technique from the literature, and implementations of both methods are provided in
the open-source Note Segmentation library.
The Simpl sinusoidal modelling library, Modal onset detection library and Note
Segmentation library were then combined to produce a real-time sound manipulation
tool called Metamorph. Metamorph is an open source software library for
performing high-level sound transformations based on a sinusoids plus noise plus
transients model. An overview of the design and implementation of the system is
provided, in addition to a collection of examples that demonstrate the functionality
of the library and show how it can be extended by creating new sound transformations.
||Sinusoids; noise; transients; spectral
analysis; feature detection; real-time
transformations; audio signals; musical
||Faculty of Arts,Celtic Studies and Philosophy > Music
||30 Sep 2013 15:58
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