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Complex Auditory Stimuli

Complex Auditory Stimuli. Complex periodic waves Complex aperiodic waves. Complex Periodic Waves. Addition of sine waves See next slide for examples Always repeat themselves over time … and therefore have a period. Always have a fundamental frequency

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Complex Auditory Stimuli

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  1. Complex Auditory Stimuli • Complex periodic waves • Complex aperiodic waves

  2. Complex Periodic Waves • Addition of sine waves • See next slide for examples • Always repeat themselves over time • … and therefore have a period. • Always have a fundamental frequency • Fundamental is the largest common denominator of a group of component frequencies • Always have harmonic frequencies • Harmonics are are whole number multiples of the fundamental • e.g., 1f, 2f, 3f, etc.

  3. Periodic Complex Waves

  4. Periodic Complex Waves

  5. Periodic Complex Waves

  6. How are complex periodic waves displayed? • Waveform • Amplitude Spectrum (line spectrum)

  7. How are complex periodic waves displayed? • Several examples of a line spectrum. The lower figure represents the vowel / i /.

  8. Fundamental Frequency • See earlier slide. Largest common denominator of a group of component frequencies. • E.g., If the the component frequencies are 500, 550, 1000, 1050, the largest number that can be evenly divided would be 50. Therefore, 50 Hz would be the fundamental. • It would also have the same pitch as a 50 Hz tone.

  9. Harmonics • Harmonics are whole number multiples of the fundamental (fo). The fundamental is always the first harmonic (1f). • May be determined by dividing the fo into the component frequency. • In the previous example the component frequencies would equal the following harmonics. • 500 Hz = 10xf (i.e., 10th Harmonic) • 550 Hz = 11xf • 1000 Hz = 20xf • 1050 Hz = 21xf

  10. Harmonics • Relationship between harmonics and overtones. • Overtones are a musical term and are related to harmonics.

  11. Complex Aperiodic Waves • Frequencies are random • Do not repeat over time • Do not have a fundamental frequency • Do not have harmonics

  12. How are complex aperiodic waves displayed? • Waveform • Amplitude spectrum (continuous spectrum)

  13. How are complex aperiodic waves displayed?

  14. How is Sound Analyzed? • Spectrogram (aka sonogram) • Sound level meter • Oscilloscope and frequency counter • Fourier and real time analyses

  15. Spectrogram

  16. Sound Level Meter

  17. Sound Level Meter • Sound Pressure Level (linear) • dBA, dBB, dBC (weighted scales)

  18. Sound Level Meter • dBA, dBB, dBC (weighted scales) • Used primarily for industrial, community, and aviation applications. • dBA scale has greatest amount of attenuation in low frequencies. • dBB scale somewhat inbetween dBA and dBC. • dBC scale has least amount of attenuation in high frequencies.

  19. Other Methods of Analysis • Oscilloscope (displays waveform)

  20. Other Methods of Analysis Frequency Counter

  21. Other Methods of Analysis • Fourier Analysis • A method of mathematically changing a waveform to an amplitude spectrum • Real Time Analysis or Fast Fourier Transform (FFT). • Fourier analysis in real time

  22. Summary

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