setPwmFrequency for attiny85

I am trying to make a little PWM PC fan controller with an attiny85 with a thermometer. It is working but at lower speeds I am getting an electronic chirping from the fan. From my experimenting with a 555 timer, this is solved by playing with the PWM frequency. There is a function for changing the PWM frequency but it does not work on the attiny85.

I get the error:

'TCCR1B' was not declared in this scope

Which I would assume has to do with different sorts of registers between the atmega and attiny. Can anyone help me get this function working on the attiny? I am using this method of programming the attiny.

Have a look here or here.