Open Speaker Model No. WA-9900
4®
Introduction
The Open Speaker is designed for the study of sound wave properties
including frequency, amplitude, pitch, wavelength, and resonance.
The rugged aluminum bracket holds the speaker perpendicular to the
table and provides two standard banana plugs for power input. The
speaker is a 5 ¼” woofer with a polypropylene cone and high
efficiency 10 oz. magnet.
The Open Speaker is designed without a speaker cabinet to reduce the
resonance of the air surrounding the rear of the speaker. This helps
students to more easily hear the resonance created in a closed or open
tube of air.
Suggested Experiments:
Equipment Required: Open Speaker (WA-9900), Economy
Resonance Tube (WA-9495), Function Generator (PI-9587C), Banana
Plugs [SE-9750 (red set of 5), SE-9751 (black set of 5)]
a) Studying Sound Wave Properties
1. Connect the Open Speaker to a function generator using standard
banana plugs.
2. Ask students to listen to the sound as you change the amplitude and
to write down the property of the sound that is changing. Help
students to mentally connect the amplitude of a sound wave to the
volume.
3. Repeat step 2, but instead of changing the amplitude, change the
frequency of the sound. Ask students for the “music” term for
frequency (pitch).
b) Resonance of an Air Column
1. Connect the Open Speaker to a function generator using standard
banana plugs.
2. Place the Economy Resonance Tube (WA-9495) directly in front of
the Open Speaker (See Figure 1 on the next page).
