Windows – Noise/hiss produced by Windows(?) on the audio output (not a hardware issue)

audiodigital-audionoisewindowswindows 10

I have a Windows 10 PC in my car that I use as a head unit for the audio system, and I'm having trouble with background noise. I have been able to detect it on another Windows 10 PC as well. The noise is NOT interference on the analog output. It must be of a software origin because I used Audacity to record the WASAPI output when nothing was playing, and sure enough the noise is there.

To clarify: the following noise samples are recorded using software only. This is not what plays from the analog output of the DAC; this is what Windows sends to the DAC.

I have recorded it from the Speakers output as well as VB Audio virtual cable output (I absolutely need the virtual cable). Interestingly, the spectrum is a bit different, but the noise is similar on both outputs.

Here are short unamplified noise samples exactly as recorded by Audacity – no tampering:

These are 16-bit recordings, so the sample value range is from -32768 to +32767. The noise is -8 to +8 peak to peak, with roughly -4 to +4 average.
Here's the waveform and spectrum of the noise:

enter image description here

What can possibly be producing this noise and how to get rid of it or at least reduce it? It may seem too quiet to be a problem, and I never heard it through headphones, but in the car where there's a good set of speakers and some amplification it can be heard quite distinctly when nothing is playing.

I can also confirm that this noise I recorded on a different PC indeed matches the feel and the character of the noise I hear in my car.

Can someone with Windows 10 download Audacity and capture their audio output in order to find out how common or uncommon this problem is?

UPDATE: I have repeated the experiment on my home laptop and desktop computers, both Win 10 as well, and have confirmed the issue there as well. All the samples I collected on these 2 systems are exactly the same, unlike my office desktop where they differ in noise spectrum a bit.

UPDATE 2: Important new findings:
1. I can hear this noise quite clearly with my home laptop via EMU 0404 USB DAC -> 35W @ 4 Ohm amp -> shelf speakers. I need to set the amp's volume to max and I can hear it then. The system becomes dead quiet when I turn the DAC off.
2. I have run a proper spectrum analysis on the noise. While its amplitude is only 8, which is -78 dB in 16 bits, but its spectrum reaches as high up as -30 dB. That explains why I can hear it: -30 is a clearly audible quiet sound on any decent system, and -40 is still audible when you sit close to the speakers (which you always do in a car, incidentally). Also, my car amp is 60W @ 4 Ohm so its gain is higher than that of my home amp (and then there's also a matter of the tweeter's sensitivity which differs for different models).

enter image description here

Best Answer

In case you haven't already, ensure all inputs have been disabled and are not part of the mix you are recording. Just because you are recording what is being sent to the DAC, doesn't mean Windows hasn't already mixed in some electrical noise on an input. In fact, I would disable the input completely and lower the recording volume on the mix to zero.

To determine if the issue is hardware or driver related, I would install a different OS on a temporary drive, or boot from a USB key (https://www.ubuntu.com/download/desktop/create-a-usb-stick-on-windows).

If the problem goes away then it is a driver issue and you may have a chance of fixing it by manually installing an different driver version, or even a generic one if it exists. There is still a small possibility that it's a hardware bug uncovered by a driver-specific feature.

If the problem persists then it's quite likely a hardware bug. I would still check where in the boot process the noise starts (power on, after hardware init and POST, during OS bootup, after the first OS sound plays, after application start). If it's after the OS starts then you may have some luck with drivers. If it's before OS startup, then there is likely not much you can do, save for a firmware update.

Good luck!

Update 1

I have recreated your results using the following steps:

  • Record the speaker output using WASAPI
  • Export the file to a WAV file
  • Open the saved file
  • Amplify +50db

The result is a significant amount of noise and the spectrum analysis has the same shape as yours.

I have also recreated the result using these steps:

  • Generate 30s of silence in Audacity
  • Export the file to a WAV file
  • Open the saved file
  • Amplify +50db

Conclusion: The sound you see is generated by the algorithm that saves the file. The sound you hear is generated elsewhere, probably typical line noise.

As proof, try recording your speaker output and before saving apply amplification. If you are using the latest Audacity you will get a value overflow error b/c it can't handle amplifying complete silence. If you have at least one non-zero value in the selection, the amplification works.

Update 2

Further proof: Try saving your recording as 64 bit raw data, and then importing it again. For me this results in a file with no noise, that cannot be amplified again.