Since this company went privatised its become a waste of time, with silly products, like THX car audio, is one of them.
http://www.thx.com/auto/index.html
The noise background level is going to be higher than any background for professional THX cinema, where they have strict guidelines; some THX cinemas lose their licence if, the (air condition system) went above a certain threshold noise level.
And they have the gore to come out with THX car audio sigh! What’s next then? THX cat food? Well my cat is, the worls first THX certified cat!
I think THX shouldn’t have gone private as the old site had some good technical white papers that are just hard to find now.