Time Stretching & Pitch Shifting of Audio Signals

Time Stretching & Pitch Shifting of Audio Signals -...

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Unformatted text preview: Microcomputer Systems 2 Time Stretching & Pitch Shifting of Audio Signals Time Stretching & Pitch Shifting of Audio Signals Outline Introduction Techniques Used for Time Compression/Expansion and Pitch Shifting Comparison Timbre and Formants February 11, 2012 Veton Kpuska 3 Outline Introduction Frequency Shift vs. Pitch Shift Audio Examples Time Compression/Expansion Techniques Used for Time Compression/Expansion and Pitch Shifting The Phase Vocoder Related Topics Why Phase Time Domain Harmonic Scaling (TDHS) More recent approaches Comparison Which Method to Use Pitch Shifting Considerations Audio Examples Timbre and Formants Phase Vocoder and Formants Time Domain Harmronic scaling and Formants February 11, 2012 Veton Kpuska 4 Introduction Time Stretching & Pitch Shifting Are two dominant techniques that used for speech and sound manipulation. Typical applications entail: Changing the speed of play-back (altering the length of the signal) without altering the pitch of the voice and/or instruments Changing the pitch of the voice and/or instruments without changing the length of the signal. Pitch Shifting February 11, 2012 Veton Kpuska 6 Pitch Shifting: As opposed to the process of pitch transposition achieved using (a simple) sample rate conversion, Pitch Shifting is a way to change the pitch of a signal without changing its length. In practical applications, this is usually achieved by changing the length of a sound using one of the methods discussed next and then performing a sample rate conversion to change the pitch. February 11, 2012 Veton Kpuska 7 Introduction Pitch Shifting is NOT Frequency Shifting: There exists a certain confusion in terminology in the literature, as Pitch Shifting is often also incorrectly named 'Frequency Shifting'. A true Frequency Shift (as obtainable by modulating an analytic signal by a complex exponential) will shift the spectrum of a sound, while Pitch Shifting will dilate it, upholding the harmonic relationship of the sound. Frequency Shifting yields a metallic, inharmonic sound which may well be an interesting special effect but which is a totally inadequate process for changing the pitch of any harmonic sound except a single sine wave. February 11, 2012 Veton Kpuska 8 Audio Examples of Pitch Shifting vs. Frequency Shifting Original Sound: Pitch Shifted: Frequency Shifted: Time Compression/Expansion February 11, 2012 Veton Kpuska 10 Time Compression/Expansion Time Compression/Expansion, also known as "Time Stretching" is the reciprocal process to Pitch Shifting. process to Pitch Shifting....
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This note was uploaded on 02/10/2012 for the course ECE 3552 taught by Professor Staff during the Fall '10 term at FIT.

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Time Stretching & Pitch Shifting of Audio Signals -...

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