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Measurement Bias

Measurement bias is the idea that if you know the measurements of something that information will already bias your perceptions of it’s performance. For instance, knowing the g-force at which car A might slip vs. car B could affect your perception. B, having a higher g-force rating should be a "better" car but if you did not know this you might rate A as better. It may be more fun to drive.

I’ve seen this happen in a review in (I believe) TAS. The review was for a DAC I purchased. The reviewer noted it as "noisy." I read this after I had purchased and been listening to the DAC for a while. I was more than a little shocked, I could hear no noise whatsoever from the DAC. I pulled out an oscilloscope and sure enough, there was unexpected ultrasonic noise on the outputs. I eventually did sell the DAC, but not because it was at all noisy, but because new DACs handled Redbook (44.1kHz/16 bit) tracks so much better. Nowhere in the review did the reviewer mention they had measured it, and they certainly did not point out the deficiencies in Redbook playback, but the reviewer absolutely presented this DAC as noisy but otherwise OK.

So, my point is, that making assessments on the experience that comes from a measurement in audio is tricky business, and if the reviewer is aware of the measurements ahead of time it will absolutely bias them into hearing things which they’d otherwise not, and leave them blind to other real world challenges.

If you want to put together desirability with measurements you need to look at the work Floyd Toole or Bose have done and others in this area and you wont’ find it in a frequency response chart. Of course, Bose’s research is proprietary, but absolutely no one one earth has spent more money on assessing value vs. measurements and manufacturing dollar than Bose.

PS - Please don't argue the quality of Bose speakers here.  I'm not arguing for or against them.  I'm arguing that the research done in tying together desirability and engineering direction is outstanding.  That is all.

erik_squires
knotscott
813 posts
 

Good point for sure. Those who rely on measurement have as much bias as someone who doesn’t (and possibly less listening skill due to neglect).    Measurement bias is basically expectation bias, and any listening that ensues (assuming that even happens), is approached with certain expectations put there by the measurement results. I 100% agree with that.

Listening works for me. If measurements need to be taken, take them after listening.

erik_squires OP
15,750 posts
 

I should point out that the opposite effect can happen as well. Using measurements and listening to gear can change your hearing. You start to hear music like a piece of test gear instead of enjoying it. I know this has happened to me. I get very good at predicting frequency response charts from listening sessions and... it doesn’t make my enjoyment of the experience any better. It just makes me more skilled at estimating frequency response graphs.

As a result of this, I know I hear differently than other audiophiles.  Is it better?  No, not really, but it is different and now I buy different gear or build different gear. 

There IS a large part of being a music listener and audiophile and mastering engineer which is about social listening and a shared experience.  The mastering engineer is trying to connect with the buyers and their gear, and vice versa.  Not with tools and technology, and yet we do need to rely on them.

bigkidz
3,322 posts
 

Not I or anyone I know have purchased any piece of equipment based on any kind of measurement.  I'll have to start asking people and see what I find out.  We build components and we do measure the parts quality to match certain parts as we believe and hear differences when we do this, but not all of the parts.

Happy Listening.

    

mijostyn's avatar
mijostyn
8,220 posts
 

One of the reasons this endeavor is so entertaining is that there are no standards for what a stereo system should sound like. It would be impossible to make them. The same speaker in three different rooms is three different sounds. Three different types of speaker in the same room are three different sounds. It is up to every single one of us to tailor our systems to sound the way we want in the room we have available within financial constraints. I personally believe principles are more important than measurements. Some measurements are more important than others, but given the range of issues related to speaker performance in situ, specifications and test measurements reside in the background.

I have said on multiple occasions, what someone says any piece of equipment sounds like means nothing to me because I have no way to interpret this. I only care what I think something, usually a loudspeaker sounds like in my room. When it comes to loudspeakers the specs are virtually meaningless, but the design speaks volumes. In many instances the specs are misleading. 

The important measurements to make are those you can make in your own listening room in regards to amplitude, group delay and dispersion. If you can't hear distortion any measurement is of no significance. If you can't hear noise any noise level is of no significance. 

 

         

mesonto
73 posts
 

Both are great, lets scientifically measure them and listen to them. You will end up picking a component that works best for you for any number of reasons. Your bias will be there regardless, for the numbers or for the brand, or for the price, or for the room you auditioned your component in, or for a reviewer, or for word of mouth, or for what you believe sounded better because of an A/B sound comparison which would mostly likely be unreliable (depending on you memory and/or chosen A/B components)... and the list goes on...

These discussions on either side are beyond ridiculous.

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