Yes, there is a HUGE problem with you posting random, off-topic stuff to our lists, and your marketing people should be aware of this (their email addresses, by the way, are publicidad@...
, in case anyone else wants to complain to them). I doubt if most people who volunteer their valuable time to run a private mailing list want to donate their subscriber list to your cause, no matter how cool you think it is or how much you think they would want to hear about it. We didn't create our lists merely to compile a list of consumer addresses to be marketed to. Haven't you ever heard of "opt-in"?
You say in the newsletter: "This is not Spam mail. You're getting this newsletter because you got in touch with us sometime in the past or because you're subscribed to a mailing list that deals with topics similar to the ones offered at Sonic Wave. Moderators, if you don't want to receive more mails like this in the future, please let us know."
WRONG. This IS spam - it is unsolicited email. Period. In the groups I received it in, your post was completely off-topic. You may not be selling something in the traditional sense, but you are trying to get people to visit your web site in order to show them your content AND advertising, which in turn makes you money. It's rude. It's also against Yahoo's Terms Of Service.
Had you followed proper netiquette, and asked permission to post a link to your web site instead so we could visit at our own leisure and discretion, I'm sure a lot of list moderators would have gladly let you, especially since your web site does look sort of interesting. But since you didn't, you now I imagine have a lot of people pissed at you.