I think you should stay away from that one, even if you didn't know where the design has come from. The bottom line is that it doesn't belong to you. You seem to be more concerned with getting caught. Copyright laws aren't written so that you can try not to get caught, they are written so that people can have a legitimate right to the things that they create and have protections in the event that those rights are violated. By using this image, you are violating the rights of fellow artists. I don't think there is anything wrong with you creating an image of headphones in a circle that is inspired by this one. It seems to me that it would actually be worth the 15 minutes you take to create a new different one than to take the risks associated with copyright violation.

Sorry, that's not what I meant at all... I'm not a designer by profession and have relatively little experience & so don't know whether copyright is really an issue with this kind of thing. Some things are obviously very tied in with branding and are iconic, but this seems such a generic image that I wondered whether I really would be treading on someone's toes and violating their rights - something I certainly wouldn't want to do.

By the way, it'd probably take me 15 hours!

You can see by the above image of just how different something like headphones can be represented iconically.

Even though you may feel that first post is generic and public domain, there are clearly several different ways to create and icon for headphones. If you're not a designer by profession, do you know of anyone that could simply take a shot at their own method of interpreting what an icon of headphones should be?

Copyright is always something to take seriously. It's sort of like speeding. You might not get caught, but you might, and are you willing to risk the fine? (… and unlike speeding the fine can be considerable.)