CLIOwin 7 PCI User's Manual - Audiomatica

12.4 MAKING A CUMULATIVE SPECTRAL DECAY
A cumulative spectral decay starts loading an impulse response from disk. Suppose we
have taken an anechoic response of a medium sized two ways loudspeaker; the impulse
response is shown in Fig.12.3.
Let's first select a reflection free part of it. By selecting the start and stop window points
we obtain the first two information parameters required for the waterfall facility: zero
time will be referenced to the start of the start window, while the Z axis will provide the
measurement range between the stop and start window points (unless a Time Shift is
chosen).
Figure 12.3
Going inside the Waterfall Settings dialog we decide to view our measurement between
150 and 20000Hz, then apply 1/12 octave smoothing. We are now ready for a
waterfall!
Figure 12.4
The Go button is enabled. Press it, you should obtain a waterfall like the one in the left
part Fig. 12.5. Press now the Color Scale button followed by the Interpolate Colors
buttons, now you should have the color map shown in the right part of Fig. 12.5. The
two representations are not exclusive, they mutually complement each other; you will
gain experience understanding all the subtle details of a waterfall processing and how
they are represented either in the 3D or in the color map. For example the color map
represents better the frequency of decaying modes as they result as straight color
patterns parallel to the time axis; the 3D waterfall is more familiar when you look at
zero time frequency plot and try to visualize how it modifies during decay.
Chapter 12 - Waterfall and Directivity 147