Acoustic testing on a budget is a daunting task. Many measurements need to be made, and sometimes several batteries of tests are required to get valid data. In the case of testing the Acoustic Ramp, I actually did an entire battery of tests that proved later to be invalid. The good news, is that I learned from my mistakes and the second battery provided good repeatable and valid data.
My test process is essentially this: Shoot a swept sine wave from a high quality studio monitor at the diffuser and record what bounces back from the diffuser with a high-quality microphone placed on the circumference of a circle with the diffuser at its center. Then I move the microphone 5 degrees along the circumference and repeat the test. Software assembles all of the data into impulse responses that when combined can create a sonogram which shows amplitude, frequency and the position of the microphone in relation to the diffuser.
Here are some photos showing the process of the testing:
