John Curl's Blowtorch preamplifier part II

[Wavebourn]

Originally Posted by bcarso

Galvanic skin response? Blood pressure? EEG?

Only half-kidding.

...they will show very personal differences in reactions on stimuli. No need for such subtle measurements. When I react on sounds before I even think that they are reproduced by electronics I know that the system is fair. But when such subconscious reactions don't happen, and I always "remember" that it is the system playing, it is not so good reproduction.

This Saturday my friend come to my house and brought his Yamaha keyboard and Apple notebook to check how well his new software samples grand piano we heard as if real piano playing in my living room. The conclusion was, the software satisfies him. But to my satisfaction I evaluated my home reproduction setup and found it to be quite satisfactory.

[SY]

Originally Posted by RNMarsh

I guess a different question might be -- is there any other way, than dbt, to hear differences or to hear anything for certain?

Not really. This is one of the most firmly established and powerful tools in sensory research (not just sound, ANY sort of sensory evaluation). And for sound, it works quite well, unless you're selling something that isn't distinguishable without peeking.

Indirect measures like Brad's examples or the MRI stuff from Japan are interesting, but difficult to debug and evaluate. One important point is that, for those sorts of indirect measurements, the matching of results versus stimulus also needs to be done double-blind.

[Jakob2]

Originally Posted by john curl

I rarely see so much repetition in a challenge, what is the point?

It´s all about scientific reasoning. It is a bit funny to require something like double blind testing for validation reasons, but to refuse on the other hand to validate the double blind test itself.

A controlled listening test relies on a listener as the detector for differences (related to our discussions on these topics), so as an experimenter you ought to know if your detector is doing well -> validate it by using positive controls (aka differences a listener must detect under test conditions) .

Otherwise there is no way to decide whether a difference remains undetected because it is not audible (means no human listener will be able to hear it) or because the listener/detector fails to detect it _under_ the specific test conditions.

[rcw666]

You can look at a double blind test as a Bernoulli trial. The one most familiar being a coin toss.

If the coin is "fair" then there is an exact equality in probability in a head or a tail and the distribution quickly converges upon a Gaussian one.

In a double blind test the idea is to eliminate systematic errors because these skew the probability towards one outcome or the other.

If for instance you set a confidence level of five percent then you are saying that your test has up to that much skew towards a particular outcome, and this is convenient because it is the area that is two standard deviations from the mean, and in the vast majority of cases you can get a test that is valid over this range.

Some people then say well your test is invalid because it has an in built uncertainty, but science being basically statistical it always will have, the question is not the presence of uncertainty but how much.
By this method you can know just how uncertain your results are and a ninety five percent chance that a null hypothesis is proven is not bad, a ninety nine percent one is even better but your test is much more difficult to do because removing systematic errors to this extent is very difficult and might well be impossible with realizable sample sizes.
rcw

[Jakob2]

Just two remarks; even if the null hypothesis could not be rejected, that does not mean that the null hypothesis was proven, it just means that it could not be rejected.

If an experimenter lowers the probability of falsepositives he raises the probability of falsenegatives (means that the power of the test goes down).

It is possible to balance the two different errors up to a certain degree, which is another benefit of using positive/negative controls.

[Chris Hornbeck]

Originally Posted by morinix

After test and measurement vetting I like Rupert Neve's method "I hook it up and play music and do other things" - Passive listening - That is, IME, the only way to distract your brain from worldly things so that that audio zen moment can grab your hearing-brain connection and get a clear evaluation. Otherwise your brain is over analyzing. May not be "legit" but it is how I roll.

I'm with you 100% on this. If this kind of listening could (easily enough to be practical) be combined with a blinding, we'd have something. If either is lacking, the whole thing retains a fishy smell to somebody or other.

Thnaks,
Chris

[Wavebourn]

Originally Posted by SY

One important point is that, for those sorts of indirect measurements, the matching of results versus stimulus also needs to be done double-blind.

And, how Dean Radin discovered in his early experiments, it is quite difficult task that can be spoiled by effects that have no logical explanation! If you remember, he analyzed data obtained from experiments when generators of true random numbers used by computer to select stimuli, but according to data he analyzed people subconsciously predicted what kind of data will be presented, in advance. Trying to find the source of this error he found that it is not an error, but rather a phenomenon that can't be explained by modern science. His current speculations involve quantum non-localities that entangle true random processes in the Universe with cognition, but it is hard to believe, despite no other explanations fit.

[john curl]

I'm with Robert Neve on this. Passive listening works for me, but I really try not to personally judge my own audio designs or anyone elses, these days. I am getting older and somewhat more tolerant to 'poor sound' , also one could be biased just because they are involved in the creation of the sound.
What I do, is pretty much electronic design, searching for the best topology for a given product. My normal work schedule is 'putting out fires' rather than sitting at the test bench, you know, sourcing parts, getting schematics proofed, etc. I use my hi fi just to listen to music, but not at the very hi fi level that I once maintained more than 20 years ago. The only real reference that I have is a pair of tube driven STAX Pro Lambda electrostatic headphones, that I sometimes use for component evaluation.
My recommendations are based on my experience, and unfortunately, on some 'failed' tests, where I could not measure much, but the general public, (and reviewers) rejected the product. I try to learn from my mistakes, and I would hope that others do not 'fail' either.

[john curl]

Scientific reasoning? I think a very small subset of 'scientific reasoning' perhaps.

[Johnloudb]

Originally Posted by SY

Not really. This is one of the most firmly established and powerful tools in sensory research (not just sound, ANY sort of sensory evaluation). And for sound, it works quite well, unless you're selling something that isn't distinguishable without peeking.

All a double blind test will tell you is that the subjects couldn't identify a difference in a blind test. It doesn't mean the differences don't exist or aren't audible.

Recently I heard a person with misophonia (dislike for sounds) complaining about someone mowing their yard far away, while he was inside his home. No one else could hear it. I hear about this all the time, and have experienced it too, of course.

Also read about a nurse who had PTSD could hear medical helicopters coming long before anyone else in the hospital could hear them, even when she'd tell them about it.

The brain turns up the gain on sounds with special meaning or importance, while others are habituated (habituation of perception) to these sounds of no significance.

I don't think the way most people go about double blind testing says much at all about what is and isn't audible.