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Chapter 5

Chapter 5. Sound Analysis. Filters Shape Spectra. Attenuating (reducing) amplitudes in certain frequency ranges Come in different types: High-Pass Low-Pass Band-Pass Band Reject. All Filters have definable:. Cutoff Frequency: Where attenuation reaches 3 dB

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Chapter 5

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  1. Chapter 5 Sound Analysis

  2. Filters Shape Spectra • Attenuating (reducing) amplitudes in certain frequency ranges • Come in different types: • High-Pass • Low-Pass • Band-Pass • Band Reject

  3. All Filters have definable: • Cutoff Frequency: Where attenuation reaches 3 dB • Rolloff: Rate (in dB/Octave) at which attenuation increases

  4. Low and High Pass Filters

  5. Band Pass and Reject Filters

  6. Example of a Filter’s Effect

  7. Gating: Turning Sounds On and Off • A tone on continuously theoretically has energy at only one frequency • Turning a tone on and off will distort it and produce energy at other frequencies

  8. Gating Terms: • Onset--When amplitude begins to grow from zero. • Rise Time -- Time taken for amplitude to go from zero to largest value. • Offset--When peak amplitude begins to decrease from largest value. • Fall Time -- Time taken for peak amplitude to go from largest value to zero.

  9. Gating Effects--Spectral Splatter • The Shorter the Rise/Fall Times, the greater the spread of energy to other frequencies. • The Longer the Rise/Fall Times, the lesser the spread of energy. • Overall (or Effective) Duration also controls spectral splatter

  10. Distortion: • Broad definition = any alteration of a sound • Specific def. = Addition of energy at frequencies not in the original sound • Devices that produce distortion are said to be “nonlinear”

  11. Examples of Distortion: • Harmonic Distortion = adding energy at multiples of input--often seen when peak-clipping occurs • Intermodulation Distortion = production of energy at frequencies which are sums and/or differences of the input frequencies.

  12. Nonlinearities • Input + additional sinusoids = nonlinear output • Additional tones are combinations tones • Summation tones (f1+f2, 2f1+f2, f1+2f2…) • Difference tones (f1-f2, 2f1-f2, 2f2-f1…) • Input + change of time-domain waveform = distorted (nonlinear) output

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