Purpose:Demonstrate interference of sound with two coherent sound sources in a quantitative way.
Description:The oscillator is set to approximately 3000 Hz, with identical signals being applied to both loudspeakers and displayed on the lower oscilloscope trace. The microphone, with its signal displayed on the oscilloscope upper trace, can be moved around to observe the interference pattern by displaying the alternating maxima and minima in the intensity pattern. Nodal and antinodal lines can be observed and measurements made to show the relationships between the wavelength, source separation, and the nodal/antinodal lines. Invite students in the audience to volunteer what they hear at different points, and compare it to what the microphone picks up.