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The invention of measurements and perception

This is going to be pretty airy-fairy. Sorry.

Let’s talk about how measurements get invented, and how this limits us.

One of the great works of engineering, science, and data is finding signals in the noise. What matters? Why? How much?

My background is in computer science, and a little in electrical engineering. So the question of what to measure to make systems (audio and computer) "better" is always on my mind.

What’s often missing in measurements is "pleasure" or "satisfaction."

I believe in math. I believe in statistics, but I also understand the limitations. That is, we can measure an attribute, like "interrupts per second" or "inflamatory markers" or Total Harmonic Distortion plus noise (THD+N)

However, measuring them, and understanding outcome and desirability are VERY different. Those companies who can do this excel at creating business value. For instance, like it or not, Bose and Harman excel (in their own ways) at finding this out. What some one will pay for, vs. how low a distortion figure is measured is VERY different.

What is my point?

Specs are good, I like specs, I like measurements, and they keep makers from cheating (more or less) but there must be a link between measurements and listener preferences before we can attribute desirability, listener preference, or economic viability.

What is that link? That link is you. That link is you listening in a chair, free of ideas like price, reviews or buzz. That link is you listening for no one but yourself and buying what you want to listen to the most.

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erik_squires
spatialking's avatar
spatialking
610 posts
 
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.  
erik_squires OP
16,056 posts
 
@spatialking

Not asking ... so much as stating a point of view and inviting others to chime in. 
Your reply is perfect.


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geoffkait's avatar
geoffkait
23,365 posts
 
Two things. What value are measurements of anything if it sound different in every room? And how can we measure audiophile goals like soundstage, air, musicality?
stevecham
3,340 posts
 
A good example of this is the redbook standard set in the late 70s early 80s for the then emerging CD format. The standard was fine, but it took until the late 90s to figure out that distortion in the time domain (jitter) was a major factor that prevented the unmeasurable enjoyment factor from CD playback. Once it was identified and measured, designers solved, or at least found ways to manage, much of this "new" type of distortion.

And to Geoff’s point above, IMO, the room accounts for at least 50% of the sound we hear from our systems.
erik_squires OP
16,056 posts
 
A good example of this is the redbook standard set in the late 70s early 80s for the then emerging CD format. The standard was fine, but it took until the late 90s to figure out that distortion in the time domain (jitter) was a major factor

Jitter is interesting. I mean, yes, we can certainly point to it as one measurement that has improved over time, and Redbook had a markedly big jump in audible performance in the last 10 years.

Is that enough? I mean, we never proved it really, and we don't actually have any idea of what is audible, or if there are other parameters around jitter which are important. I mean, AFAIK, there's not even an agreement from manufacturer to manufacturer as to how exactly jitter is measured.

So if jitter IS the problem ... what is inaudible?


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