Logarithmic amplitude scaling of a signal

16 views (last 30 days)
Lorenzo Lellini on 13 Feb 2023
Answered: Jeffrey Clark on 14 Feb 2023
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
figure(1)
plot (out, 'LineWidth', 1.5)
hold on
plot(t_input, amp)
grid minor
3 CommentsShow 1 older commentHide 1 older comment
Jeffrey Clark on 13 Feb 2023
@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 on 13 Feb 2023
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?

Jeffrey Clark on 14 Feb 2023
@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.

Categories

Find more on Octave in Help Center and File Exchange

R2022b

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!