Oscillations and Waves > Waves > Phase and Group Velocity DCS# 3B30.50
SPEED OF SOUND IN DIFFERENT GASES
APPARATUS
organ pipe 202-05-G
water manometer
 202-alcove
T-connector
 202-05-G
gas cylinder and regulator
 013A
compressed air
 201A

DESCRIPTION
Compare pitches for an organ pipe blown with compressed air and with other gases at the same pressure.  Hear pitch rise or fall depending on the type of gas.
When CO2 is used, v is about 20% lower than for air, so pitch drops about 20% (3 semitones in the musical scale).  Pitch rises when helium or argon is used.  The pitch also depends slightly on gas pressure so a manometer is used to see that pressures are the same in each case.