Turnable database with TimeLine

It is the Dr. Feickert iPhone app. It requires a test record with a 3150Hz test tone, or now the app will also recognize a 1000Hz test tone. I happened to have a test record with the 3150Hz test tone; but Dr. Feickert's test record can be purchased at their online shop.

I think this app is excellent. Just start playing the test tone and the app will react to the tone and ask to start recording. It plots frequency versus time and has a bar at the top that helps you to dial in speed. Once you save a plot the app analyzes the data and gives you average speed, raw WoW&Flutter as well as filtered Wow&Flutter. It is easy to filter out the record's contribution to WoW&Flutter due to eccentricity of the center hole since the period is 1.8 seconds. But the app does all that for you. The filtered plot shows you raw and filtered frequency over time. For example, my record gives a frequency plot with the peaks going from 3160Hz down to 3140Hz (my test record center hole is not very well placed). The filtered line or the actual tt performance shows shows frequency right on 3150Hz with slight waves about that line. That is the +/-0.02% or -0.6HZ/-0.7Hz variation that the chart shows me.
I tried this app with my CD player too. I had a test disc with a 1000Hz tone. The app showed a perfect flat line at 1000Hz with WoW&Flutter at 0%.

Just for the sake of argument about calibration of the iPhone's microphone. I downloaded an FFT app a few years ago. FFT is a method of analyzing a noise spectrum. It plots frequency vs. amplitude. I was at an automaker's NVH lab one day a few years back. This is a Hemianechoic chamber for measuring noise levels and frequency on a car. (If you are amazed at how quiet your car is, then I may have had a little something to do with that on one little component. If you are not too pleased with the sounds your car makes, well then someone else must have worked on that model). They had their B&K calibrated test tone source used for verifying microphone amplitude calibration sitting there. It generates a 1000Hz tone. So I turned it on and checked my iPhone's calibration (just for frequency, not amplitude). The app was dead on. These apps utilize the iPhone's internal oscillator/clock for calibration. Frequency accuracy should not be a problem for an iPhone app; but amplitude (SPL) is a different matter. I would not count on the iPhone's mic for exact amplitude measurements.

Well, not only that but the tension produced by the belt would constrain isolation effectiveness of both platforms.

Dear Lewm, Dear Peter,
I would like to answer you but I cannot. My ideas, thoughts and experimentation results cannot be seen the way I want it.
sorry.

I did lose something it turns out. After dark when the ambient noise level was at its lowest, I could hear some rumble. It is faint; but there. So the bushings are transmitting some mechanical vibration from the chasis to the sub chassis. I have some ideas to try out. I can't go back to an unconstrained horizontal axis...