4-24-09

Class today was devoted to demonstrating the properties of sound waves.

Before beginning his first demonstration, Mr. Manning had to make sure that nobody in the class was epileptic/seizure prone or sensitive to intensely bright, flashing lights since the demonstration required the use of strobe lights. The aim of this demonstration was to show the class the visual properties of sound waves by matching up the frequencies of tuning forks to the frequency of the strobe light. With the classroom lights off and the strobe light pulsating, it was as if the room went from a physics class to a bumpin' club scene. With the frequencies synced, Manning struck the tuning fork causing it to vibrate. With the strobe light flashing on and off, the tuning fork was fleetingly visible, dramatizing the motion of the prongs and giving them the appearance of swaying back and forth - the pitch from the fork being a result of the vibrations.

In another demonstration, Mr. Manning struck a tuning fork and held it to a hollow wooden block which amplified the pitch. This demonstration revealed that the vibrations that create the pitch can be transmitted and carried through other objects - the resonance of the transmitted sound depending on the acoustic properties of the medium trough which it is carried through. Another demonstration addressed the capabilities of the human ear to hear pitches ranging from high to low in correlation with the frequencies of the waves that produce them. Using an audio generator, Manning produced various pitches, starting from a relatively low frequency and ending with a pitch which our ears are unable to hear due to the high frequency at which it travels.

About half way through the period, Mr. Manning turned the floor to Julius Sumner Miller, who conducted a multitude of demonstrations that addressed the concepts of pitch and frequency.