Hardware-induced Noise If Charging Device Via USB Port

[TonyVA408]

I suppose this is not really considered an Audacity-specific issue, but since certain recordings might be affected, I thought I'd mention this.

I've noticed that when I charge my Samsung Android smartphone using a USB port on my PC, a certain kind of noise can clearly be heard through my PC's audio outputs particularly when the phone is fully charged. The noise is especially noticeable when listening with headphones. What kind of noise? For you folks old enough to remember, when a vinyl record plays through and the stylus is left to continue riding on the inner-most end of the groove, that's what this noise resembles. Similar sound, same pace.

Since my PC speaker volume is set low (just 30%), at first I hadn't noticed. But then, during a very quiet evening moment, I realized there was a strange noise coming from somewhere. At first, I didn't even suspect the PC. However, turning up the volume or listening with headphones made the noise much more noticeable, of course.

Unplugging the phone makes the noise stop immediately. I have no idea whether this noise can affect recordings while using Audacity, but since I can charge my phone in other ways, it didn't seem necessary to test.

In case it's a problem unique to my PC manufacturer, note it's a ZT Systems desktop system running Windows 7.

Good luck, folks, and as always, many thanks to the Audacity team. I just made another donation, too.

Tony M.

[kozikowski]

You can make it worse if you charge your phone that way but leave it charging next to the cables in your sound system. You can hear it burble every time it "phones home" to make sure the connection is still there. It's distinctive.

Perfectly normal. Any time you get analog sound equipment like speakers, microphones, amplifiers, phonographs, etc, you could get buzzing, clicking, whining or interference. USB equipment uses the 5 volt battery in the connection to run things. In your case, the phone uses the 5 volt battery system to charge.

If it was a perfect, stiff, well-regulated 5 volts, there would be no trouble, but it's not. It's usually sloppy and works somewhere around 5 volts. Every time your phone needs a little of it, it sags a little slightly below 5 volts and then recovers.

Every one of those sags is going to appear in your sound system. Be clear it's not getting into your computer, it's getting into the speaker amplifier which is analog, not digital. The digital services don't care at all.

I had an iMic USB sound adapter that I put in a box in the garage. I could tell every time my hard drive changed speeds because I could hear the whiny sound in the show.

So even though it says in the book this should work, it only works from the point of view of the phone. That works fine.

Use your wall or car adapter. Much better.

Koz

[TonyVA408]

Thank you, Koz, for such an in-depth reply. I well-understood your points. I also appreciated the distinction you made between the digital aspects of sound processing and the analog portions.

Thank you again and good day.

Tony M.