20hz 0dB tone

I think it means that you will not be able to hear it but can feel it. My brother is an engineer for Lockheed Martin and brought home an ossciliscope (is that how you spell it) and was playing around with it on his Velodyne sub. He turned it down to like 25 HZ, you could not hear it but it rattled all the dishes in the house. Kinda of reminded me of the sound of an earthquake (not the subwoofer). I think that is what it means.

 

Because we can't hear below 20hz and we can't hear above 20,000 hz. By "we" I mean people.

 

When my brother played it, it was freaky, could not hear it but everything in the house was rattling like a small earthquake. For those of you who have not lived through an earthquake, it is a bizarre sound. If its small enough you can hear everything rattling but might not feel it, I guess you just have to experience it to know what im talking about. Playing a tone like that replicated the feeling perfectly.

 

i think it means it is the full signal not attenuated. i've seen -3db -10 db.

 

Well CC what did it sound like? Didnt it rattle everything? If I remember right my brother was using 2 Velodyne 12 inch sub being run off of 2 NAD power envelope amps. I thik he was trying to set the xover points, but I remember it rattled everything in the house.