The concept: methods – content – objectives - Signals, Processes, and Systems - page 11

Analog- out

Analog-in

Addition Time domain FFT Fr eq. dom ain

Plotter

LP 1000 Hz At tenuation Delay

Illustration 14: S-frame diagram and signal block in the time domain

The above illustrates a combined echo-hall-system for the low frequency range. This block diagram was
also compiled on the screen from standard components - called up from a library - and linked together.

Certain parameters must be set by mouse-click for some of the components, for example the lowpass filter
(4 and/or 8), the cut-off frequency and the filter order. The input signal goes directly to "oscilloscope" (13)
(see screen below left) and to the PC speaker (12). Parallel to this the input signal is lowpass filtered (4),
weakened (5) and finally with a time delay (6) is added to the input signal (7) ("echo“). The sum of both
signals is fed back to the inlet, after the operations described above have been carried out (8), (9), (10), (3)
("reverb"). The program with the linked algorithms is running in the background and carries out the echo-
hall effect on a real level.

An echo device produced by DASYLab is described below. The production of echoes is also a branch of the
feedback phenomenon which contains the three "components" lowpass filtering, delay, damping (multipli-
cation by a number smaller than 1).

Turn on the microphone and loudspeaker of your PC. Click on to the picture and the DASYLab experimen-
tal laboratory opens immediately. Start the experiment and go on experimenting to your heart's content.