Digital Signal Processing Reference
In-Depth Information
Illustration 69:
“Waterfall”-representation of the sequence “I owe you“
The entire sequence has been divided up into individual sections which have, as in Illustration 52, a gentle
beginning and ending (weighting with a GAUSSian window). The word begins in the uppermost line and
ends at the bottom. The "i"-phases, the "o"-phase and the transition phases between them can be clearly
discerned. The frequency spectrum of each section is calculated (Illustration 70).
This is carried out in Illustration 70 where a particularly impressive technique - the
"waterfall analysis" - is employed which presents a landscape-like, three-dimensional
picture of the frequency-time landscape of this word. If windows overlap - which, as I
have demonstrated in Illustration 51 and Illustration 52, is the case here - the 3D-land-
scape must contain all the information of the overall signal "I owe you" because the con-
nection between the individual segments has not been disrupted. Hence, the first
important results are:
A vowel can be characterised as a
near-periodic segment
of a
"word signal". In other words, it also has a "line-like" spectrum.
The longer it takes to pronounce, the more clearly it can be iden-
tified. The shorter the period of pronunciation, the less clearly it
can be identified (
UP
!). An extremely short vowel would just be
like a crack.
