Murilo

rajama, have you predicted the effects of Helium over the loudspeaker parameters ? While helium's density is has 0.137 times air's density and speed of sound in Helium is about 3 times FASTER than in air, Sulfur Hexafluoride (SF6) is in the opposite extreme. SF6 has a density 5.1 times higher than air's density and speed of sound 3 times SLOWER than in air. I have predicted some advantages from it's use. I created a long html page that describes my conclusions, my thoughts and the known facts. Please have a look: http://murilo.dyndns.org/audio/gas.htm Please send me your critics (by forum or email). I have more material. Do you think the main energy dissipation comes from: (a) the heat generated by the compression of air or (b) by the vibration (deflection) of walls? What about energy dissipation on enclosure with ideal gas? The highlight below explains that sound propagation in ideal gases is an adiabatic process (no heat will be generated or lost). Do you think this will also be valid for the lower frequencies inside a sealed enclosure filled with ideal gas ? In case it is valid for all frequencies, then the energy inside it will stand untill an object absobs it (a damping material or the enclosure walls). http://hyperphysics.phy-astr.gsu.edu/hbase/sound/souspe3.html "When a sound travels through an ideal gas, the rapid compressions and expansions associated with the longitudinal wave can reasonably be expected to be adiabatic." Regardless of this fact, an SF6 enclosure aided with damping material may reach your goal. The slower sound speed and higher density of SF6 will make the absorbtion of sound energy by a damping material more efficient. Reasons: - The waves will remain for longer at a given "damped area" before leaving it - The damping material will "shake harder" due to the higher density OBS: I suppose that the lenght of the movement of molecules in SF6 would be the same as in air.