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I was getting some odd sounds from a samples library I had which lead me to test Scope's DSP.

I used the control room and used a sine wav and Spectrogram to see what was happening to the audio path..

I started at 1kHz and all looked correct, then I tested it at between 15 and 16kHz ,where I was getting odd sounds. It seemed that there were some sidebands occuring rather than a pure single sine wave.

I will test it more but if I'm getting a side band or two at a certain frequency then God knows what else is being added to a harmonic signal.

Any views?

Thanks

uhh!! tell us more!

bad woofer?

something resonating in the room?

or something viewable on the scope?

How are you actually testing this? How do you know you are not overloading the spectogram?

yes. please post a screemshot and explain more

Well here is the same sort of thing from my cheapo audio laptop card:
@ Gary - It's all internal Gary.

what and where is this measurement?

i'm not confrontational, just confused.

garyb wrote:what and where is this measurement?

i'm not confrontational, just confused.

I didn't take it negatively Gary.

Ok, I set up a sine wave to pass through the audio drivers which is picked up by the spectrogram.

What I am asking is, why is the spectrogram showing sidebands when the sine wave is supposed to be a pure signal.

I tested this because I was getting some "fluttering" affect. I've just replaced the drivers and everything sounds as clear as a bell.Yes they were corrupt.

The wierd thing is that I still get the sidebands as a result. They are very bad in the Lows and lower mids and begin again at about 15.5kHz.

So my question is: What noise is being added to the audio signal?

I can't believe how bad the sound was and how flakey things got when the drivers were corrupted.

sure, corrupted code won't function correctly or at all...

the sine wav itself may not be very pure. it's hard to say what's happening from the info...

tricky thing a fft is;
there are no sidebands at all;

good vibes

tgstgs wrote:tricky thing a fft is;
there are no sidebands at all;

good vibes

What's that noise that's showing though?

FFT approximation?
FFT should give different approximation with different sample block size (also different approx @ different frequencies)

cheers
Fede

i dont know spectograph;

but what i see (the bands around 100Hz or 1kHz) is a mathprobl. _ there is no noise!
the fft doesnt care about frequency its a mathmodel put on;
-------
use a higher N to get less 'noise' or apply a window before fft;
if interested do a search for _ julius von hann _ hanning window _ to get an idea

good vibes from vienna

using rightmark audio analyzer i got "excellent" across the board with 24/44 with a16 plugged back in to itself.

Hi,

If you are getting a ringing metallic tone superimposed to your sound, there is a good chance that your scope have partly lost its synch.

change your sample clock (cycle from 44,1 to 96 then go back). There is a good chance it fail. In my config this is a symptom of a bad sitted STDM cable / board.


cheers

Michel

MD69 wrote:Hi,

If you are getting a ringing metallic tone superimposed to your sound, there is a good chance that your scope have partly lost its synch.

change your sample clock (cycle from 44,1 to 96 then go back). There is a good chance it fail. In my config this is a symptom of a bad sitted STDM cable / board.


cheers

Michel

Are things really that volatile?
So many things can go wrong..

Not that much (once or twice a year). One of my STDM connector get loose after a time (the one associated with the 1rst connector on the board) and exhibit this problem

cheers