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