One typical party trick that has since become rather unoriginal is that of inhal
ID: 1399800 • Letter: O
Question
One typical party trick that has since become rather unoriginal is that of inhaling some helium from a party balloon and then speaking with an unusual tone of voice. We would like to examine this phenom- ena further. (a) The velocity of sound in a gas can be found by the square root of RT /m vsound = M Where =adiabatic constant = 5/3 for He, R = 8.314 J mol·K (1) , M = the molecular weight of the gas in kg/mol, and T =absolute temperature (in Kelvin K). Look up a value for M and use it along with a temperature that corresponds to room temperature to find vsound in helium. (b) What is the ratio of the speed of sound in helium to that in air at room temperature? (c) Manypeoplewouldsaythatthepitchofthevoicehaschanged(tobehigher),butthatisn’tentirely true. Actually what has happened is that the “timbre” has changed and certain resonant frequencies are now enhanced while others are diminished. Suppose we think of the voice box as a closed tube chamber of some constant length, and moreover that the vocal folds displace the gas particles surrounding it in the same way regardless of the type of gas around it; what (using mathematical arguments) about the sound waves is altered? One typical party trick that has since become rather unoriginal is that of inhaling some helium from a party balloon and then speaking with an unusual tone of voice. We would like to examine this phenom- ena further. (a) The velocity of sound in a gas can be found by the square root of RT /m vsound = M Where =adiabatic constant = 5/3 for He, R = 8.314 J mol·K (1) , M = the molecular weight of the gas in kg/mol, and T =absolute temperature (in Kelvin K). Look up a value for M and use it along with a temperature that corresponds to room temperature to find vsound in helium. (b) What is the ratio of the speed of sound in helium to that in air at room temperature? (c) Manypeoplewouldsaythatthepitchofthevoicehaschanged(tobehigher),butthatisn’tentirely true. Actually what has happened is that the “timbre” has changed and certain resonant frequencies are now enhanced while others are diminished. Suppose we think of the voice box as a closed tube chamber of some constant length, and moreover that the vocal folds displace the gas particles surrounding it in the same way regardless of the type of gas around it; what (using mathematical arguments) about the sound waves is altered? One typical party trick that has since become rather unoriginal is that of inhaling some helium from a party balloon and then speaking with an unusual tone of voice. We would like to examine this phenom- ena further. (a) The velocity of sound in a gas can be found by the square root of RT /m vsound = M Where =adiabatic constant = 5/3 for He, R = 8.314 J mol·K (1) , M = the molecular weight of the gas in kg/mol, and T =absolute temperature (in Kelvin K). Look up a value for M and use it along with a temperature that corresponds to room temperature to find vsound in helium. (b) What is the ratio of the speed of sound in helium to that in air at room temperature? (c) Manypeoplewouldsaythatthepitchofthevoicehaschanged(tobehigher),butthatisn’tentirely true. Actually what has happened is that the “timbre” has changed and certain resonant frequencies are now enhanced while others are diminished. Suppose we think of the voice box as a closed tube chamber of some constant length, and moreover that the vocal folds displace the gas particles surrounding it in the same way regardless of the type of gas around it; what (using mathematical arguments) about the sound waves is altered?Explanation / Answer
The speed of sound in helium is about 972 m/s, compared to 331 m/s in air. This is consistent with the general relationship for sound speed in gases since the density of helium is so much less than that of air.
The speed of sound in helium is 2.94 times greater
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