Measuring the Sound Color


Sound Color = Spectrum Analysis

The basics for a good sound color detection lies in spectrum analysis. The spectrum of a song describes how much a certain frequency is present within the song. However, weighing different frequencies and making something useful from a spectrum analysis is not as straight forward as expected.

The Bark Frequency Scale

The first thing to note is that the human ear is very well suited to detect certain frequencies. Especially in the range of the human voice we are very capable of hearing well. However, on the higher frequency ranges (above 11500 Hz), humans are unable to distinguish different frequencies. Therefore, to correctly describe the sound color of a song we need to take into account how well the human ear perceives these frequencies. Luckily, such a scale exists and is called the Bark Scale.
  • 0-100
  • 100-200
  • 200-300
  • 300-400
  • 400-510
  • 510-630
  • 630-770
  • 770-920
  • 920-1080
  • 1080-1270
  • 1270-1480
  • 1480-1720
  • 1720-2000
  • 2000-2380
  • 2380-2700
  • 2700-3150
  • 3150-3700
  • 3700-4400
  • 4400-5300
  • 5300-6400
  • 6400-7700
  • 7700-9500
  • 9500-12000
  • 12000-15500
  • Measuring The Spectrum

    The spectrum of a song is measured over 10 seconds at the last used cue-position. The strength of the different frequencies is measured and exported as 24 bands of the bark-scale.

    Similarity Detection

    To measure how close two song-)colors are we take the L^2 norm, which is the sum of the squares of the differences of all different bands.

    Determining the Sound Color

    The sound color itself is created by a principal component analysis. This is described in more detail in [WVB--REF].

    Cluster Analysis

    [WVB --TODO]

    Copyright (c) Werner Van Belle December 2001
    e-mail: werner.van.belle@vub.ac.be
    Tel: +32 486 68 84 48; Fax: +32 2 629 35 25
    http://bpmdj.sourceforge.net/