dietermoreno
- Dec 30, 2012
- 238
- Joined
- Dec 30, 2012
- Messages
- 238
Weird behavior of audio interface at 20 KHZ.
I was experimenting with recording a 20 KHZ tone from YouTube to Audacity using an audio interface. Unfortunately, the interface does not record what it is playing (possibly anti-piracy motivated), so I over come that by the analog loop hole of...literally a loop...a 6 inch instrument cable connected from headphone jack to guitar jack.
I can not hear the tone on YouTube, but the strange results it causes to my interface and recorded in Audacity allows me to detect the presence of the tone.
All that appears to be recorded in Audacity is crackles occuring about every 2 seconds. The crackles stop existing when the 20 HZ tone is not played.
bizzare. its almost like the transistors in the audio interface are treating the 20KHZ tone as a radio signal and demodulating it, with spotty results in the demodulation.
Funny thing is, the higher I turn up the gain on my interface, the faster the crackles occur, untill at full gain the crackles begin oscillating infinitely faster and infintely louder from -40 db at a lower gain to -5 db at the higher gain, they are oscillating faster and louder without me even turning the gain up any more!
What I was trying to do was prepare an analog loop hole recorded track for uploading to YouTube with ultra sonic random noise to attempt to confuse YouTube's piracy algorithms and also attempt to even crash YouTube's piracy algorithms in hopes that it can't even handle 20KHZ and will go up in smoke.
Does this mean that my interface even though it says it has a sample rate of 48 KHZ (24 KHZ audio signal), it actually can't handle 20KHZ and demodulates 20KHZ like some sort of regen radio detector?
So is this deceptive marketing that although its ICs can sample frequencies up to 24 KHZ, its audio amplification can not handle 20 KHZ?
Either that or Audacity is what is broken. No I couldn't hear the 20KHZ tone, but that is intentional that no one can hear it, hence the phrase "ultra sonic random noise to attempt to confuse YouTube's piracy algorithms".
I was experimenting with recording a 20 KHZ tone from YouTube to Audacity using an audio interface. Unfortunately, the interface does not record what it is playing (possibly anti-piracy motivated), so I over come that by the analog loop hole of...literally a loop...a 6 inch instrument cable connected from headphone jack to guitar jack.
I can not hear the tone on YouTube, but the strange results it causes to my interface and recorded in Audacity allows me to detect the presence of the tone.
All that appears to be recorded in Audacity is crackles occuring about every 2 seconds. The crackles stop existing when the 20 HZ tone is not played.
bizzare. its almost like the transistors in the audio interface are treating the 20KHZ tone as a radio signal and demodulating it, with spotty results in the demodulation.
Funny thing is, the higher I turn up the gain on my interface, the faster the crackles occur, untill at full gain the crackles begin oscillating infinitely faster and infintely louder from -40 db at a lower gain to -5 db at the higher gain, they are oscillating faster and louder without me even turning the gain up any more!
What I was trying to do was prepare an analog loop hole recorded track for uploading to YouTube with ultra sonic random noise to attempt to confuse YouTube's piracy algorithms and also attempt to even crash YouTube's piracy algorithms in hopes that it can't even handle 20KHZ and will go up in smoke.
Does this mean that my interface even though it says it has a sample rate of 48 KHZ (24 KHZ audio signal), it actually can't handle 20KHZ and demodulates 20KHZ like some sort of regen radio detector?
So is this deceptive marketing that although its ICs can sample frequencies up to 24 KHZ, its audio amplification can not handle 20 KHZ?
Either that or Audacity is what is broken. No I couldn't hear the 20KHZ tone, but that is intentional that no one can hear it, hence the phrase "ultra sonic random noise to attempt to confuse YouTube's piracy algorithms".