Additional Info

• ID Code: H1-26
• Purpose: Direct measurement of the speed of sound in air.
• Description: Two microphones at the ends of a section of garden hose (wound around a metal drum for convenience) are connected together electrically with their output fed into an oscilloscope. Tapping one of the microphones with a small hammer produces the pulse at the left in the photograph above; the second pulse is that tap after traveling through the air to the other microphone. The length of the hose is about 14.4 m, and the time interval measured from the scope trace is about 40 ms.

  Note: This is related to H1-24: Speed of Sound in Helium. These can both be used in a single class, but can require some time to switch over. This can be a good project for in-class discussion, giving students the opportunity to make predictions and discuss while the gas is changed. This can also be an opportunity to introduce concepts related to measurement uncertainty and propagation of error. For a shorter demonstration, use H1-26 alone to make a single measurement.

• Availability: Available
• References: REFERENCES: (PIRA unknown.)
• Loc codes: OS7, ME2