The article you referenced is using a C-weighted scal where audio competitions use an A-weighted scale. The difference being that the A-weighted scale gives more credit for lower frequencies therefore 150 db at a car stereo competition would be more like 115db to 130db on a C-weighted scale. I have hit 141db (A-weighted) using 2 12's and 600 watts but a Boein 747 is 136db (C-weighted) at take off. The Boeing is ALOT louder in reality. The reality of sound is that as frequencies drop below 100HZ the volume vs. pain threshold climbs at an inverse exponential rate. The lower the frequency the highe the volume level required to produce hearing loss and pain.