 At 169 m / s , the speed of sound in xenon gas is lower than that in air due to the lower average speed of the heavy xenon atoms compared to nitrogen and oxygen molecules . Hence , xenon lowers the rate of vibration in the vocal tract when exhaled . This produces a characteristic lowered voice timbre , an effect opposite to the high @-@ timbred voice caused by inhalation of helium . Like helium , xenon does not satisfy the body 's need for oxygen . Xenon is both a simple asphyxiant and an anesthetic more powerful than nitrous oxide ; consequently , many universities no longer allow the voice stunt as a general chemistry demonstration . As xenon is expensive , the gas sulfur hexafluoride , which is similar to xenon in molecular weight ( 146 versus 131 ) , is generally used in this stunt , and is an asphyxiant without being anesthetic . 
 At 169 m / s , the speed of sound in xenon gas <a href='drop_aux' title='1'><mark>is</mark></a>lower than that in air due to the lower average speed of the heavy xenon atoms compared to nitrogen and oxygen molecules . Hence , xenon <a href='uninflect' title='2'><mark>lowers</mark></a> the rate of vibration in the vocal tract when exhaled . This <a href='uninflect' title='3'><mark>produces</mark></a> a characteristic lowered voice timbre , an effect opposite to the high @-@ timbred voice caused by inhalation of helium . Like <a href='negative_concord' title='4'><mark>helium</mark></a> , xenon <a href='uninflect' title='5'><mark>does</mark></a> not satisfy the body <a href='null_genetive' title='6'><mark>'s</mark></a>need for oxygen . Xenon is both a simple asphyxiant and an anesthetic more powerful than nitrous oxide ; consequently , many universities no longer allow the voice stunt as a general chemistry demonstration . As xenon <a href='drop_aux' title='7'><mark>is</mark></a>expensive , the gas sulfur hexafluoride , which <a href='drop_aux' title='8'><mark>is</mark></a>similar to xenon in molecular weight ( 146 versus 131 ) , is generally used in this stunt , and <a href='drop_aux' title='9'><mark>is</mark></a>an asphyxiant without being anesthetic . 
At 169 m / s , the speed of sound in xenon gas lower than that in air due to da lower average speed of the heavy xenon atoms compared to nitrogen and oxygen molecules . Hence , xenon lower the rate of vibration in tdavocal tract when exhaled . dis produce a characteristic lowered voice timbre , an effect opposite to the high @-@ timbred voice caused by inhalation of helium . Like no helium , xenon do not satisfy the body  need fa oxygen . Xenon is both a simple asphyxiant and an anesthetic more powerful den nitrous oxide ; consequently , many universities no longer allow thdaoice stunt as a general chemistry demonstration . As xenon expensive , the gas sulfur hexafluoride , which similar to xenon in molecular weight ( 146 versus 131 ) , is generally used in this stunt , and an asphyxiant w/o bein anesthetic .