REFLECTING ON THE ACTIVITY AND THE CHALLENGE

Music is made up of many different frequencies. The human ear is capable of hearing many frequencies. It would be great if the music coming from a speaker were the same as the music created. One way to determine the job that a speaker can do is by comparing the input of many different frequencies with the output of those frequencies. A good speaker will give a "flat frequency response." If no frequency is favored in the input, then no frequency is favored in the output. When you make decisions about the dance concert, you want to ensure that good music is not turned into bad music because you have changed the frequency response. As you decide how to protect the hearing of the people attending the dance, you also want to protect the quality of the music.

PHYSICS TO GO

1. Explain the concept of frequency response.

2. Below is a list of audio devices. Tell which has a frequency response. Remember that something with a frequency response has both an input and an output.

a) a personal tape player

b) a doorbell

c) an alarm clock

d) a radio

3. Look at the graph (on page M37) that shows the test of a speaker's frequency response.

a) At what frequency is the response the greatest?

b) If you were listening to music through this speaker, what would be the effect of the "peak" between 100 Hz and 300 Hz?

4. Sketch a frequency response curve for an excellent speaker.

5. Explain how logarithmic graph paper is helpful in plotting graphs of frequency response.

6. When purchasing speakers you will want to know the frequency response curve of the stereo system. The graphs below show frequency response curves for three stereo systems.

a) For each system, describe the frequency response in words.

b) Which system would you buy? Why?

7. Refer to the graphs showing the frequency response of an ideal stereo.

a) How did the frequency response you measured for the stereo system compare with this ideal response?

b) Would you say the stereo system in your class is a good system? Why?

8. Look at the graph on page M37 of the speaker tested by the Consumers Union. How does the accuracy of this speaker compare with the accuracy of the stereo system in the classroom?