generate signals with different SNR

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nauman
nauman 2018-1-13
评论： Shae Morgan 2020-10-30
Hello all
I need to generate random white Gaussian noise of 3 second length. I also need to add 03 sinusoidal (say 10 KHz) pulses of 100 ms duration and SNRs of 1 dB, -10 dB and -20 dB respectively at random locations in 3 sec length Gaussian noise.
Can any one kindly help me with MATLAB code?
Also how can i verify the results i.e. the required SNR has been generated?
Thanks
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nauman
nauman 2018-1-14
My sampling rate is 100 K samples/s. This will result in 300 K samples for 3s length signal
nauman
nauman 2018-2-3
Any help in this regard is highly appreciated plz.

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Shae Morgan
Shae Morgan 2020-8-7
编辑：Shae Morgan 2020-10-30
Here's a solution! Hope it's helpful
%setup
fs=100000;
noise_dur=3;
sine_freq=10000;
sine_dur=.1;
t=0:1/fs:sine_dur-1/fs;
snr=[1,-10,-20];
sine_samps=sine_dur*fs;
%generate noise
noise=randn(fs*noise_dur,1); %generate gaussian noise
norm_noise=noise./max(noise); %scale noise
rms_noise=rms(norm_noise); %get the rms amplitude to which the sines will be compared
%generate the 3 signals at the 3 SNRs and check
for i=1:length(snr)
amp=10^(snr(i)/20)*rms_noise;
x=sin(2*pi*sine_freq*t);
xt(i,:) = (x./rms(x)).*amp;
check_snr=20*log10(rms(xt(i,:))/rms_noise)
end
%set random location 1
a=1;
b=length(noise)-sine_samps;
idx1=round(rand()*(b-a)+a);
%get random location 2 that doesn't overlap with 1
overlap=1;
while overlap==1
idx2=rand()*(b-a)+a;
if idx2<=idx1-sine_samps || idx2>idx1+sine_samps
overlap=0;
end
end
idx2=round(idx2);
%get random location 3 that doesn't overlay 1 or 2
overlap=1;
while overlap==1
idx3=rand()*(b-a)+a;
if idx3<=idx1-sine_samps || idx3>idx1+sine_samps
if idx3<=idx2-sine_samps || idx3>idx2+sine_samps
idx3=round(idx3);
overlap=0;
end
end
end
%set the locations of the stimuli and pad zeros in between
[loc,idx]=sort([idx1 idx2,idx3]);
pad1=zeros(loc(1),1);
pad2=zeros(loc(2)-loc(1)-10000,1);
pad3=zeros(loc(3)-loc(2)-10000,1);
pad4=zeros(length(noise)-loc(3)-10000,1);
stim=[pad1; xt(idx(1),:)'; pad2; xt(idx(2),:)'; pad3; xt(idx(3),:)'; pad4];
%combine,play,and plot final sound
final=stim+norm_noise;
sound(final,fs)
plot(final) %stimulus is masked by the noise
plot(stim) %plot to see the stimuli
  5 个评论
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Daniel May
Daniel May 2020-10-29
I believe:
final=stim+noise;
should be:
final=stim+norm_noise;
-Daniel
Shae Morgan
Shae Morgan 2020-10-30
@Daniel - thanks for catching! I updated to reflect this

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nauman
nauman 2018-1-19
Hi all
Any help plz?
Thanks

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