Optional Unit V: Sound
C. Characteristics of Sound

2. Pitch

Key Concepts

Pitch is a term used to describe the frequency of sound waves.

The normal range of human hearing is from about 20 Hz to 20 000 Hz.

Frequencies below 20 Hz are infrasonic, while those above 20 000 Hz are ultrasonic.

Infrasonic and ultrasonic sounds are used in some important applications.

Doubling the frequency will raise the pitch by one octave (on the scientific scale or on the equal tempered scale).

Only certain special devices (i.e., a tuning fork) are capable of producing sounds having a single frequency. (When first struck, a tuning fork produces overtones, but they disappear quickly.)

Learning Outcomes

Students will increase their abilities to:

1. Define the following terms: pitch, infrasonic, ultrasonic.

2. Explain that pitch is a term used to describe the frequency of sound waves.

3. State the approximate range of audible frequencies for humans.

4. State some important applications for ultrasonic and infrasonic sound.

5. Explain that doubling the frequency will raise the pitch of a sound by one octave.

6. Explain that only certain devices, such as a tuning fork, are capable of producing sounds having a single frequency.

Teaching Suggestions, Activities and Demonstrations

1. Examine the characteristic qualities of a tuning fork by observing the resulting sound pattern on an oscilloscope. Compare this sound to other sounds produced by musical instruments and noise.

2. Tape record the sound of a tuning fork. Using an oscilloscope connected to a microphone, compare the sound of the tuning fork and the taped signal. Does the sound quality recorded on tape correspond exactly to the sound quality of the original tuning fork?