The invention of measurements and perception

I am not sure what you are asking - can you clarify the discussion issue? 

As for designing the measurements, once the amplifier or speaker designer has something in mind to improve the sound, it isn't too hard to create a measurement plan to quantify it.   The real problem is figuring out what to measure rather than how.   Once you measure it, it isn't too hard to run that sonic problem into obscurity. 

I'll give you an example, when I first started designing stereo amplifiers, I discovered how much power supply noise affected sound quality.  Measuring the power supply noise and relating that to sound quality was done both on the test bench as well as in listening tests.   What I found was an interesting number - the sum of the PSRR of the amplifier plus the noise regulation of the power supply has to be greater than 100 dBV.   If the power amplifier has, say 60 dBV of PSRR, then the power supply has to produce at least another 40 dBV of regulation.   All these numbers are at worst case loads for Class A or Class AB amps.  

Doing this in a solid state preamp isn't too hard, doing this in a vacuum tube preamp is harder but readily doable, doing this in a big power amp with a ton of current capacity is really hard and expensive.  

Actually, jitter is a problem just not the only problem.    Industry knew it was a problem in the very early days, there was a lot of discussion on how much was too much.   The fact is, the best jitter removal back then was not enough.
There are numerous ways of taking measurements in a room when one is putting something into production.   But for the audiophile, you only need your ears.  :-)

I studied a formula for jitter and how it relates to human perception some years back.   I'd have to go look it up as I don't recall it exactly; the limiting number is related to the number of bits and the sample rate.   Increasing the number of bits and/or the sample rate makes it more critical.  The reason it is so audible is it affects the zero crossing of music, something to which the ear is especially sensitive.  The Redbook standard at 44KHz and 16 bits is less than 50 picoseconds.   Clearly, we have a ways to go to make jitter a nonissue.

I can tell you the reason we have jitter problems, besides the fact that the basic CD clocks are not all the accurate, is the sample clock is encoded in the data stream.   The clock is not a separate signal path from the data which makes jitter an inherent problem in the system.   Whether this was known or considered an issue when the CD system was originally conceived is a good question. 

When Sony designed the CD, a number of weaknesses were created in the design due to the size limitations of the CD.   Sony's president, whose name I have forgotten, wanted it to easily fit into a car stereo and also wanted Vivaldi Four Seasons to fit on a single disk without flipping it over or inserting another disk.   This set a limitation on the sample rate, not to an advantage, and the number of bits, also not to an advantage since they had to fit all the music onto a small platter.   The original concept was to have a CD the same size as an LP since the stores were already shelved and geared for that size. 

To be fair though, at the time the CD was designed, our technology and semiconductor processes were really pushed to develop a good quality, low distortion, inexpensive DAC at 16 bits and 44 KHz.   I believe 18 bits and 50 KHz was about the limit, given the cost limitations.   I sure wish we had that in a CD, though!

As for measuring jitter and tuning fork accuracy, we have time base standards that can easily resolve better than 1x10^-14 seconds - way beyond what a human can perceive.   They are pricey but they can do it.   Gosh, the digital time base standard I have on my bench, which I bought for RIAA measurements, measures to less than 1x10^-6 seconds and is still in calibration, and that was surplus at $50!

Erik - how do you figure 1 Ampere at 1 watt has a S/N of 90dB?   There is no S/N correlation between Amperes and Watts.  

@jea48 - Actually, if one were to measure the linearity of the amplifier without loop feedback from min to max, there is a very good correlation to the timbre of sound.  However, in order to do that, you have to be the designer of the amp and have it gutted on the test bench.   Not very practical....

@edstrelow - for that you will have to become a member of AES and read up on their publications.    Once in while, they do have a good paper that correlates cabinet movement to tweeter movement.  

"... taking CDs or LPs out of the house improves the sound. Quite a bit, actually. Very shocking. ... " 

Clearly, it is time for me to leave this discussion.