Logarithmic amplitude scaling of a signal

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Lorenzo Lellini
Lorenzo Lellini 2023년 2월 13일
답변: Jeffrey Clark 2023년 2월 14일
I need to logarithmically scale the amplitude a sinesweep signal from at the starting frequency to at the lastest frequency (it should be 12 dB per octave).
Is this code wrong? Why if I plot the exponential shape and the scaled signal the profiles does not overlap?
duration_sweep = 2; % Seconds
% Sine sweep frequency range
f_start = 100;
f_end = 10000;
% Settings sweeptone
duration_final_silence_sweep = 0.1; % Secondi
total_duration_sweep = duration_sweep + duration_final_silence_sweep ;
sweep = sweeptone(duration_sweep,duration_final_silence_sweep,Fs,"SweepFrequencyRange",[f_start f_end]);
% Time axis
t_input = (0:numel(sweep)-1);
% Scaling factor
amp = logspace(log10(0.1*10^-3), log10(10), length(sweep));
% amplitude scaling
out = sweep.*amp';
% Plot
plot (out, 'LineWidth', 1.5)
hold on
plot(t_input, amp)
grid minor
  댓글 수: 3
Jeffrey Clark
Jeffrey Clark 2023년 2월 13일
@Lorenzo Lellini, you are also using the length of sweep four your amp but sweep includes the silence duration as indicated in sweeptone documentation.
Lorenzo Lellini
Lorenzo Lellini 2023년 2월 13일
ok, thank you! I forgot to specify Fs but I had already considered it...
How can I perform the procuct between amp and the sweeptone in a correct way since I must specify a silence duration in the sweep and vectors must have the same length?

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Jeffrey Clark
Jeffrey Clark 2023년 2월 14일
@Lorenzo Lellini, note that your curve is assuming a full scale sweep of +/- 1 whereas sweeptone produces +/- 0.5 so you need to plot 0.5*amp. And as in my comments above, you need to exclude fix(duration_final_silence_sweep*Fs) bins from the end of sweep.

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