Investigation of digital audio manipulation methods

Trevorrow, B. (2013) Investigation of digital audio manipulation methods. [USQ Project]

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Abstract

This project investigates the application of signal processing techniques to three unique situations: 1) the extraction and suppression of a melody in a digital recording, 2)changing the tempo (time stretching) of a polyphonic musical recording without changing its pitch and 3) the reconstruction of audio waveforms which have been truncated (clipped) due to sample values exceeding full scale detection.

Each of the applications under investigation requires the implementation of signal processing algorithms. The melody extraction/suppression application is performed through the implementation of digital filters which target the harmonic components of a musical note. Four filters are examined: the finite impulse response filter, the two pole resonant filter, the notch filter, and the infinite impulse response bandstop filter.
The constant pitch time stretching application investigates two techniques: the phase vocoder and overlap-add. Finally the truncated waveform reconstruction application investigates the effectiveness of using low pass filtering and interpolation. All algorithms are implemented using a high level programming language and the performance of these algorithms is measured using a combination of quantitative and qualitative
assessment.

The melody extraction/suppression algorithms are shown to be capable of extracting and suppressing a melody to a certain extent, their effectiveness being dependent on the type of instrument which is being filtered. The truncated waveform reconstruction techniques proposed show only limited success, capable of removing clipping in simple waveforms with only minor amounts of clipping. The three time stretching techniques
all manage to successfully change the speed of a digital recording without changing its pitch, however each technique introduces their own distinct audible artifacts.


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Item Type: USQ Project
Item Status: Live Archive
Faculty / Department / School: Current - Faculty of Health, Engineering and Sciences - School of Mechanical and Electrical Engineering
Supervisors: Leis, John
Date Deposited: 09 Apr 2014 23:38
Last Modified: 10 Apr 2014 03:17
Uncontrolled Keywords: digital audio; manipulation methods
Fields of Research : 09 Engineering > 0906 Electrical and Electronic Engineering > 090609 Signal Processing
09 Engineering > 0906 Electrical and Electronic Engineering > 090699 Electrical and Electronic Engineering not elsewhere classified
URI: http://eprints.usq.edu.au/id/eprint/24622

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