Phy 100 Lab Report 3 "Speed of Sound Determination"

Great Basin College

Introductory Physics (PHY 100) Fall 2012

Lab 3: “Speed of Sound Determination”

Introduction:

When a flute is played, the air inside the flute resonates at a specific frequency depending on where the player has placed their fingers and adjusted the length of the air column. When a tuning fork is held over an open ended tube with the lower end closed, the sound waves are forced into the tube, travel to the bottom and return back to the top by a reflection or echo of the sound. If the wave coming back is exactly in step or phase with the action of the tuning fork, a resonant condition is setup. This is constructive interference. If the tube is longer or shorter than this certain length, the sound coming back to the tuning fork will be out of phase with the motion of the tuning fork and destructive interference occurs. If somehow the length of the tube could be adjusted as the tuning fork is held over the open end, a point is reached where resonance occurs and the sound increases noticeably. This occurs when the length of the tube is a quarter wavelength of the sound wave. Lets call this special length L. We know:

Vsound = (frequency)(wavelength)

and L = wavelength / 4

Vsound = (frequency)(4L)

By forcing vibrations from a tuning fork into a tube with adjustable length and taking measurements on the length when the resonant condition occurs, we will be able to determine the velocity of sound in air.

Procedure:

Place a vibrating tuning fork over the open end of a sound tube and listen for a resonant point as the effective length of the tube is adjusted by varying the water level in the tube. This is accomplished by allowing water into the closed end of...