Vibrational Frequency and Pitch Sound Sound is generated

Vibrational Frequency and Pitch

Sound • Sound is generated whenever an object vibrates and there is a medium such as air to transmit the sound. • Sound is a series of compression and rarefaction waves. • Pitch- sound frequency

Pitch • Our interpretation of the frequency of a sound wave. Sound Frequency.

Frequency • The number of complete cycles (wavelengths) per second.

Pipe on Desk activity • Determine the relationship between the length of the pipe, the vibrational frequency/ pitch. • What happens to the frequency/pitch when the pipe is long? • What happens to the frequency/pitch when the pipe is short?

Materials • • • Long plastic pipe. Pen, marker, or pencil Tape 4 x 4 wooden block Blank white paper

Procedure • Hold the end of the pipe, with out a pen taped to it, over the edge of your desk and “twang” it at different lengths, one short and one long. Notice the sound produced with each change in length. • Decide on two different lengths for your pipes between 25 and 50 cm. Record these lengths. • Hold the pipe against the 4 x 4. • Gently “twang” the end of the pipe like a guitar string. • Another person should be slowly pulling the paper across as the pipe vibrates. • Calculate the frequency of the waves produced.

Conclusion • Count the number of wavelengths over a 1 cm distance for both your short pipe length and long pipe length. • Compare the number of waves you got for the longer pipe length to the number of waves you got for the shorter pipe length. • What is the relationship between pitch and vibrational frequency?