tags: ece-402 dsp spectral-analysis

Time-Varying Spectral Analysis

Time-Varying Spectral Analysis is a method of [spectral analysis] that generates a series of [amplitude] and [frequency] [envelope]s that describe a [sound].

• kind of an oxymoron: [Fourier transforms] already utilize time; you can't take a Fourier transform of just one sample
• trying to analyze sound as we perceive it: over a period of time

Time-varying analysis methods offer various degrees of information on the [partial]s within a [spectrum], including:

• partial amplitudes
• partial frequencies
• partial [phase]s
  • in steady tones, phase does not matter (Ohm, 1843). Ex: [Hilbert Transformed Square Wave]
  • However, in the [transient]s of noises, phase can drastically alter the [timbre] of a sound
  • frequency is derivative of phase
  • ex. glottal pulses in speech

Types

There are 2 main types of time-varying spectral analysis:

1. [Long Window Time-Varying Spectral Analysis]
2. [Short Window Time-Varying Spectral Analysis]

Sources

• ECE 402 UIUC: Electronic Music Synthesis