of Microprocessors

484 MUSICAL ApPLICATIONS OF MICROPROCESSORS
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Fig. 14-2. Filtering action of a digital integrator (cont.). (C) Graphs for Fig.
14-2 (A). (D) Graphs for Fig. 14-2 (8).
Therefore, inasmuch as an integrator is a type of analog low-pass filter, an
accumulator is a type of digital low-pass filter.
As an example, consider the tables and plots of Fig. 14-2. A digital
integrator is implemented by simply adding input samples to an accumulator
and providing output samples that are the present content of the accumulator.
As an experiment, two different strings of sine wave samples are
tried. The first string represents a sine wave with a frequency 1/20 of the
sample rate, while the second string has a frequency of 1/10 Fs. The
amplitudes of both input waves are identical. The resulting tables and graphs
give the response of the digital integrator to these strings of samples. Note
that the lower frequency wave comes out with approximately twice the
amplitude of the higher-frequency wave. Also note that the output wave lags