Turnable database with TimeLine

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...

I overreacted. The last record that I played the other night must have had noisy vinyl. I listened last night and heard no rumble. I cranked up "For Duke" again. This record has dead quiet vinyl. Sounded great- saxophones and trumpets all over the room.