A story very similar to this appeared on advrider about 18 months ago suggesting trail riding bans in the Alt Pirineo Natural Park. I subsequently went to the area and found no restrictions in place other than temporary seasonal restrictions on some trails liable to surface damage, and the author of the report would not respond to questions regarding the origins of his information.

As far as I can make out, the "noise" ban is a proposal in a similar fashion. There is nothing I can make out relating to any moto-restrictions on the Alt Pirineo park website.
I suspect the report is drawing attention to a proposal in order to build up some opposition, or at least discussion.

I would go ride and enjoy the beauty of the area. Abide by official signs if there are any, and stick to the stunning main roads that run through the park if you have any doubts. This natural park is only a small area in the mountain range, and there are not that many tar roads running through it anyway, so unless you are going round in circles a lot, any ban will not have a great effect on your journey.

In this area, as in all off-tar riding, I think noisy 2 stroke enduro bikes (which Spain is plagued with) are more of an issue, although loud sportsbikes and the Harley cruiser crowd on the main roads are equally obnoxious.