How will the fundamental frequency of a closed organ pipe be affected if instead of air, it is filled with a gas heavier than air?

Explanation

The fundamental frequency of note produced by a closed organ pipe is `v=(upsilon)/(4l)`
where `upsilon` is velocity of sound in air.
When air is replaced by a gas heavier than air, value of `upsilon` decreases `( :' upsilonprop(1)/(sqrt(rho))` where `rho` is density of the gass). Hence, fundamental frequency of the note will decrease.