I want to scale the frequencies in an audio file by a certain multiplier, without changing the run time. One of my friend told me to use Audacity version 2 . how can I use it for this purpose?
Effect menu > Change Pitch
http://manual.audacityteam.org/man/Change_Pitch
Note that changing the pitch without changing the tempo requires “time stretching” which is a difficult and imprecise task so there will be some sound quality loss.
A more advanced version of time stretching is available in the “Effect > Sliding Time Scale / Pitch Shift” effect. This version is more complicated but often produces higher quality http://manual.audacityteam.org/man/Effect_Menu#slide