Intended for teacher demonstrations only. The Rubens' Tube is a 2m long aluminium tube with a row of small holes drilled along the top and 20W loudspeaker mounted at one end.Full instructions included.Users will need a gas source (Natural or LPG) and a power signal generator to run the speaker.Speaker: 20W 8ΩGas supply Natural gas or Propane (40 millibar max)