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 Rolloff: Rate (in dB/Octave) at which attenuation increases

Low and High Pass Filters

Band Pass and Reject Filters

Example of a Filter’s Effect

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

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.

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

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”

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.

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