how to remove unwanted sound in a certain frequency range

Can you tell me how to rid of this unwanted section? thanks

Use either the 'Marquee' or 'lasso' tool to highlight it all, and hit Delete. Job done...

thanks Steve, it works nicely

I've found that you can use the gain knob that pops up to do a really nice subtle job, and lower the area by, say 25dB instead, and it sounds a lot more natural.