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Sound Processing

Sound Processing. 3rd practice Medical Informatics Biomedical Signal Processing TAMUS , Zoltán Ádám zoltanadam_tamus@yahoo.com. D/A converter. Output device. Basics of signal processing. Electrical signal. Conputer processing, storing. Input device. A/D converter. Binary number.

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Sound Processing

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  1. SoundProcessing 3rdpractice Medical InformaticsBiomedical Signal Processing TAMUS, Zoltán Ádám zoltanadam_tamus@yahoo.com

  2. D/A converter Output device Basics of signal processing Electrical signal Conputer processing, storing Input device A/D converter Binary number Signal processing

  3. Digitalization • Sound, biological signal (function of time) • Sampling • Quantization

  4. Sampling • Problem: Losing information in the interval between samples! • Nyquist-Shannon theorem: fs>2f, 2Ts<T • fs: sampling frequency • Aliasing: when the Nyquist-Shannon equation is not satisfied • Movie: the wheel rotate „contrariwise”

  5. Quantization • Ordering numbers to samples • Nearest value

  6. Quantization • Quantization • Problem: losing of the values between steps

  7. Recovered signal The difference between the original and the recovered signal is the quantization noise

  8. Signal-to-Noise Ratio • Important: The useful part of signal is not covered by noise • Signal to Noise Ratio (SNR) • SNR=6,08n+1,78 [dB] • n: the number of bits of the converter („the resolution of the amplitude axis”)

  9. Example: digitalizing of the sound • Frequency range • Shannon theory • Dynamic Range • Signal-to-Noise Ratio

  10. What is the sound? The sound is a mechanical wave which is generated by a vibrating object and propagated through a medium. The propagation method of the sound is longitudinal wave because the motion of individual particles of the medium is parallel with the energy transfer direction of the wave.

  11. What is the sound? • Main properties: • Frequency • 0-20 Hz: Infrasound • 20 Hz-20 kHz: Sound • 20 kHz-1 GHz: Ultrasound • 1 GHz- 10 THz: Hypersound • Sound pressure • Deviation from local ambient pressure [p; unit: Pa] • Intensity • Sound power per unit area [I; unit W/m2]

  12. What is the sound? • Sound Intensity Level [LI unit: dB]: • I0=10-12 W/m2 • Sound Pressure Level [LP unit: dB]: • p0= 20 μPa

  13. What is the sound?

  14. What is the sound? Fletcher-Munson curves

  15. Exercise • Using an audio processor program software: Audacity http://audacity.sourceforge.net/

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