bigshot
Headphoneus Supremus
That sounds like even MORE fun!
just don't sue me if you have to turn it up to >90 dB SPL to overcome room noise from hiding the low tone
So what if I made a sound clip with a 500 Hz square wave at -86 dB super imposed onto 6--10 kHz noise with RMS at -6dB. Is that the situation you are describing?
Cheers
% sampling frequency f=44.1e3; t=[1:10*f]/f; % create the signal at 0dB FS ys = 2*double(sin(2*pi*500*t)>=0)-1; % create gaussian noise (white) at 0dB RMS ynn=randn(size(t)); % FFT stuff for bandpass filtering the noise NFFT = length(ynn); N=NFFT; n = [1:NFFT]; Fnn = f*(n-1)/NFFT; Fnn((n-1)/NFFT >= 1/2) = Fnn((n-1)/NFFT >= 1/2) - f; Ynn = fft(ynn',NFFT, 1)/N; % bandpass filtering from 6kHz--10kHz Flow = 6000; Fhigh = 10000; Ynnf = Ynn; Ynnf(Fnn<=Flow & Fnn>=-Flow)=0; Ynnf(Fnn>=Fhigh | Fnn<=-Fhigh)=0; ynf = ifft(Ynnf*N,NFFT,'symmetric')'; % synthesize the two signals, the squarewave at -92 dB FS and the bandlimited noise at -12 dB FS dBs = -92; ys = ys * ((10^(dBs/20)) /std(ys)); dBn = -12; ynf = ynf * ((10^(dBn/20)) /std(ynf)); y = ys + ynf ; % plot waveform and spectrum figure(1); pwelch(y,[f*2],[f],[],f); set(gca, 'Xscale', 'log'); figure(2); plot(t, y); xlabel('Time, [s]'); ylabel('Amplitude, [-]'); % note, the noise energy is distributed across 6--10kHz... one must integrate the power to get the total noise energy. % check dB level disp([num2str(20*log10(std(y))), 'dB']) % >> -12dB % write to audio file wavwrite(y,f,'test_500Hz-92dB_8kHzNoise-12dB.wav') wavwrite(ys,f,'test_500Hz-92dB.wav') wavwrite(ynf,f,'test_8kHzNoise-12dB.wav') [ys_import, Fs, nbits] = wavread('test_500Hz-92dB.wav'); figure(3); pwelch(ys_import, f*2, f, [], f); % end code
Are you sure you got the right files? They all look like the same spectrum to me...
http://cdn.head-fi.org/4/45/455ab1b7_audacity_spectra.jpeg
I'm trying to understand jitter better and so far I thougt that it's not the same as noise.
I also asked because the guy who measured this says that it's audible.
I'm trying to understand jitter better and so far I thougt that it's not the same as noise.
I also asked because the guy who measured this says that it's audible.
THD+N plots tell you what the combined distortion products + noise is for a given input signal; hence, they include all effects from noise, harmonic distortion, and jitter. You will notice that identifying jitter on these plots is extremely difficult because it is often swamped out by other factors.
I'm trying to understand jitter better and so far I thougt that it's not the same as noise.
I also asked because the guy who measured this says that it's audible.