I'm curious about the nature of this scale http://images.anandtech.com/reviews/gadgets/apple/iphone4/bars.jpg http://images.anandtech.com/reviews/gadgets/apple

I'm curious about the nature of this scale http://images.anandtech.com/reviews/gadgets/apple/iphone4/bars.jpg http://images.anandtech.com/reviews/gadgets/apple/iphone4/ba... . Why does it have bar widths of (left to right) 6, 4, 2, 10, 40 dB? How does the logarithmic scale explain that, if it does?