trigonometry question

Hi,

\draw[ultra thick, red] plot (\x, {sin(deg(exp(ln(\fmin)+\x/\xmax*(ln(\fmax)-ln(\fmin)))*\x))} );

this function draws more waves from low to high frequency.
I would invert the picture.
I would draws it from low to hight frequency.
what I must change?
I'm not able to understand the function.

TIA
Renato