Mountaineers who estimate the speed of sound by hand clapping, find the speed of sound to be nearly the same as at sea level. Up a mountain at 1500 m, the pressure will be about 25% less than at sea level.This will creep back up to room temperature with a corresponding movement of the signal on the screen. In step 2, there will be a drop in temperature if the vacuum pump rapidly reduces the amount of air in the tube.This experiment shows that it would not as long as it is only the pressure which changes. You can ask students whether the speed of sound would change at different altitudes in the atmosphere.After re-evacuating, admit some carbon dioxide and the speed will show a marked decrease.After pumping out as much air as possible, admit natural gas and it will be found that the speed of sound is greater.This shows that the speed of sound is independent of pressure. The signal should not have moved across the screen, but it should have a lower amplitude. The pulse received by the microphone should be displayed on the screen. Set the Y-gain of the oscilloscope to about 0.1 V/cm and the time-base to about 1 ms/cm.Either fill a balloon first, or blow the gas through the open tube.
Place a little cotton wool in the tube to dampen out any standing waves and make the display clearer.ĭo not admit carbon dioxide directly from a cylinder to the tube: this may blow out one of the bungs. One of the bungs should also be pierced by a glass tube, which is connected by pressure tubing to the vacuum pump. At the other end of the tube there should be leads running through the bung to the microphone, so it can be connected to the oscilloscope. The output from the calibrated time-base of the oscilloscope is fed via the amplifier through the bung in one end of the tube to the earphone or loudspeaker. Read our standard health & safety guidance Reduce the risk by ensuring that there are no possible sources of ignition in the vicinity.
#SPEED OF SOUND THROUGH AIR MANUAL#
Vacuum pumps and gas cylinders are heavy: the Manual Handling Regulations must be complied with.Ī methane-air mixture, 5 litres in volume, presents a possible fire hazard.
#SPEED OF SOUND THROUGH AIR HOW TO#
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