We cover the third approach to stimulus-response experiments: excitation by noise. We apply random noise to the acoustic cylinder and measure its response.
We measure the autocorrelation function of the response and find that it resembles the ring down we obtained in response to pulse excitation. Fourier transform of the autocorrelation or the raw signal yields the power density spectrum of the acoustic cylinder.
To prepare for this lab read about the autocorrelation and convolution vis in The LabVIEW help files for each of these functions. The lecture notes are available as a handout in front of Rm 204 Bagley.
Click here to receive a vi that will help you understand the concept of noise excitation.