| Hi,
Will you please assist me with the following questions? Please see the code
below. I have looked in several books and online sources and haven't
received complete answers yet.
A. When viewed in a time-domain representation, why does gbuzz create
impulses with square tops (examples 1 and 2) and buzz does not (examples 3
and 4)? I thought that gbuzz and buzz would yield the same results when
klh=kmul=1 in gbuzz.
B. In a frequency-domain representation, I see where examples 2 and 4 seem
to have very sharp (i.e., brick wall) low-pass filters on them with a cutoff
at 1280 Hz (i.e., num_of_partials*fundamental). Are examples 2 and 4
properly called "bandlimited impulses"?
C. If 2 and 4 are properly called bandlimited impulses, is it correct
terminology to say that they are "bandlimited at 1280 Hz"?
D. Examples 1 and 3 are simply the latter half of bandlimited impulses. Does
using the latter half of a bandlimited impulse have a name in the DSP world?
E. In a frequency-domain representation, I see where examples 1 and 3 look
like they were passed through a resonant low-pass filter with a peak at 1280
Hz (i.e., num_of_partials*fundamental), at which point it also starts to
roll off. Does this sort of impulse have a name? Perhaps "resonant low-pass
filtered impulse"?
F. Would impulses such as examples 2 and 4 be related to sinc filters?
Specifically, if normalized, could they be used as impulse responses for a
sinc filter (i.e, would they act as a sinc function)? If so, is that process
just a matter of convolution? I tested it by convolving example 4 with white
noise and it indeed low-pass filtered the noise at 1280 Hz with a very sharp
cut-off (it wasn't a perfect filter, but it worked quite well). Is this a
typical approach for sinc filtering?
Thank you very much in advance. I appreciate it!
Sincerely,
John
-odac
sr = 44100
ksmps = 32
nchnls = 1
0dbfs = 1
gicosine ftgen 0, 0, 2^14, 11, 1
gisine ftgen 0, 0, 2^14, 10, 1
instr 10
asig gbuzz 0.5, p4, 128, 1, 1, gicosine, p5
out asig
endin
instr 20
asig buzz 0.5, p4, 128, gisine, p5
out asig
endin
i10 0 0.05 10 0.0 ; Example 1 -- Duration is ((1/fundamental_freq)/2) and
phase is 0 degrees.
i10 1 0.10 10 0.5 ; Example 2 -- Duration is (1/fundamental_freq) and phase
is 180 degrees.
i20 2 0.05 10 0.0 ; Example 3 -- Duration is ((1/fundamental_freq)/2) and
phase is 0 degrees.
i20 3 0.10 10 0.5 ; Example 4 -- Duration is (1/fundamental_freq) and phase
is 180 degrees.
--
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