acoustics2 slides - HSLS 250 HSLS 250 Speech Science Basic...

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Unformatted text preview: HSLS 250 HSLS 250 Speech Science Basic acoustics 2 Last week: Last week: Sinusoidal wave Amplitude & loudness 1 f= Period, frequency & pitch T Propagation velocity c = fλ Wavelength Not all waves are Not all waves are sinusoidal Sounds can be different even with the same frequency, amplitude, and phase Today’s outline Today’s outline Complex waves Fourier Analysis Repetitive vs. non­repetitive waves Quality: Complexity of Quality waveform Quality difference in Quality difference in speech Quality difference? Quality difference? Quality difference is characterized by presence of additional frequencies Fourier analysis: Part 1 Fourier analysis Any periodic waveform, no matter how complex it is, can be closely approximated by adding together a number of sinusoidal waveforms Synthesizing a complex Synthesizing a complex wave Decomposing a complex Decomposing a complex wave Fourier analysis: Part 2 Fourier analysis: Part 2 The set of sinusoids that one adds together to approximate a particular complex waveform are harmonically related Harmonics Harmonics The components of a periodic complex wave are whole number multiples of fundamental frequency (f0) These multiples are called harmonics Harmonics and f0 Harmonics and Harmonics are whole number multiples of f0 n­th harmonic = n f0 f0 is the greatest common denominator (GCD) of the frequencies of harmonics For example For example Harmonics: 100 Hz ( f0 ), 200 Hz (2 f0), 300 Hz (3 f0) f0 = 100 Hz Frequency is not enough Frequency is not enough A complete specification of a complex wave includes the frequency and amplitude of component sine waves Spectrum Spectrum Graphical representation of the sinusoid components of complex waves Specifies the frequency and amplitude of components Examples of line spectra Examples of Why Fourier analysis? Why Fourier analysis? Our auditory system performs a similar analysis that enables us to distinguish sounds of different quality Fourier analysis in cochlea Fourier analysis in cochlea (inner ear) Same components, Same components, different Waves Phase indifference Phase indifference For different complex waves, as long as their components are the same, we hear them as the same sound Non­repetitive waves Non­repetitive waves Spectra of non­repetitive Spectra of non­repetitive waves: Continuous Repetitive vs. non­ Repetitive vs. non­ repetitive waves Repetitive waves: Line spectrum Non­repetitive waves: Continuous spectrum ...
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This note was uploaded on 05/08/2011 for the course HSLS 250 taught by Professor Lee during the Winter '10 term at Ohio University- Athens.

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