why the slope of gain is -6dB/octave

[ampper]

6 db per octave per decade

why the slope of fequency response of gian in Gray's book is -6dB/octave?

i know the slope is -20dB/decade, and i calculate it as follows

slope=-20dB/(log8x-log810x)
=-18dB/octave

what's wrong with my calculation?

Thanks!

 

[IanP]

octave how to calculate slope

6 dB per octave (20 log2) <=> 20 dB per decade (20 log10) ..

Regards,
IanP

 

[ampper]

6 dB per octave (20 log2) <=> 20 dB per decade (20 log10) ..

Regards,
IanP

Thanks for your quick reply and your picture ！
And now i understand it.