Activity 2.6 - Standing waves in air, air column

• Understanding standing waves in closed-end air column
• Investigate the resonance frequencies of standing waves

• Sound generator
• Tube
• Stand material

In activity students examine the resonance frequencies of a closed-end column.

By changing the frequency of the signal generator the frequency at which air inside of the tube is also changing. When the frequency of signal generator is closed the natural frequency of the air column then resonance occurs and a loud sound results.

It is up to the teacher to what extent the students are supported in this experiment.

• How can you, for a certain length of the tube, be sure to have the lowest frequency required for resonance?
• Draw the standing wave patterns for the fundamental frequency and the first three harmonics.
• What would happen with length of the air column or frequency if the speed of sound is changed?
• Predict what the effect will be for the frequency if the temperature is changed.