What are we objectivists missing?

Well, this did not go in the direction I had intended, but I suppose I should not be surprised.  I guess the take away for me is "We don't know what we don't know".

Thanks anyway.

Well, your question didn't make sense. 

My take is that if you can hear a difference, there must be some difference.  

Not necessarily, depends if bias has been accounted for. 

So what are your opinions on what those differences might be and what are we NOT measuring that would define those differences?

We can measure the audible spectrum for humans. We can even measure the spectrum for dogs and dolphins so I have no idea what your asking for. 

We can measure the audible spectrum for humans.

It is one parameter, this measure dont limit the complexities of perceived sound qualities in multidimensional neurophysiological analysis as such and by itself alone, but this measure limit only the physical range of our perceiving abilities on an external physical scale in decibel.......Sound is not only defined by decibels range...

Not necessarily, depends if bias has been accounted for.

here too you forgot the difference between the positive biases of a musician and confuse it with the negative buyer of an audio product..

Then if we can hear differences they can be expression of LEARNED biases then positive one, or delusion then negative biases... Acoustician and musician exhibit learned biases...

Thing are not always simplistic in two cases: true or wrong......

Blind test on musicians had demontrated their ability to beat the uncertainty principle in Fourier analysis ..

https://arstechnica.com/science/2013/02/human-hearing-beats-sounds-uncertainty-limit-makes-mp3s-sound-worse/

«This problem has been highlighted in a recent Physical Review Letter, in which researchers demonstrated the vast majority of humans can perceive certain aspects of sound far more accurately than allowed by a simple reading of the laws of physics. Given that many encoding algorithms start their compression with operations based on that simple physical understanding, the researchers believe it may be time to revisit audio compression.»

We can measure the audible spectrum for humans. We can even measure the spectrum for dogs and dolphins so I have no idea what your asking for.

You are confusing "listening" skills with "hearing" abilities. Not sure if on purpose or by mistake

There is an art to listening.