High Noise Spectrum above 13kHz

[Merz]

Hi,

I've made a audio track of 60Hz and another audio track at 7kHz. After which I used the mix and render function to mix the two audio signal together. I've got a nice spectrum display up to 13kHz, however if you see the attachement file, the noise level at the spectrum above 13khz is rather hight. Using of the equalization function in the software doesn;t improve the situation better. What can be done to improve this section of the spectrum?
Thanks.

[steve]

Set the sample depth to 32 bit.
(Edit menu > Preferences > Quality tab).

Audacity processes audio at 32 bit, so if your tracks are at a lower bit depth, dither noise will be produced.

[Merz]

Hi,

Actually the defualt setting for the sample format was already set at 32 bits float. But you have given me a good ideal to investigate the dithering effect on the waveform. I look up at your website and understood that the shape provide a good listening quality but at the compensation of noise at higher frequency which is not sensitive to human ear, and this was actually the setting I was using. By trying and error, I realised that "rectangular" has the best audio performance for my signal.

Thank you.

[kozikowski]

I was going to comment that -125 dB is not "High Noise." It's extraordinarily low noise and I would expect some odd digital error to be involved. It way beyond what most analog audio amplifiers can do.

Koz