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Fletcher-Munson - Random Variables and You

We have regular discussions about loudness controls, and Fletcher-Munson curves here, so I thought it would be interesting to use that to talk about the problem with testing and human variability.

To simplify, the Fletcher-Munson curve comes from a paper in 1933 which showed that as volume goes down, our hearing changes. It gets worse at the edges and more pronounced int he midrange. A general overview is here:

https://en.wikipedia.org/wiki/Equal-loudness_contour

Now, this is science, and I’m sure they did the best they could, but FM as have the multiple studies after them, have come to different values for these curves (but they agree in principle). What’s worse, the loudness curves are different for front hearing (speakers) than side-hearing (headphones).


Why should we care? Well, these curves are all averages, gathered over samples that are probably not that random. I mean, how many women, how many people over 65, and how many from the Australian outback were tested? Your personal F-M curve I guarantee is different from the curves published by F-M or the studies after. These curves are derived from random samples, they are not indicative of any actual person’s hearing.


So... this means that as we listen to and buy equipment, we need to understand that our own hearing is not like anyone elses. What we are sensitive to, and what we spend money on is different and that’s what it means to be human. For instance, I’m really sensitive to frequency response and room acoustics. I am completely insensitive to absolute phase and phase shift in the speaker.


We are all different and I hope we can all make room for science and engineering as well as the fact that what brings us joy and pleasure of ownership is going to vary a great deal. An average measurement from a study may not tell us a thing about you individually.

Best,

E
erik_squires
erik_squires OP
16,910 posts
 
If I intentionally delay the subs just 0.5 msec (5 feet at sea level) You will hear and feel it easily when I switch back and forth. This puts 100 Hz 180 degrees out of phase right at the crossover point. Instant mess.

That is no longer phase sensitivity, that’s frequency response sensitivity, which most people are sensitive to. I was not referring to this at all, and that’s easy to show in any system.

Comparing Thiel and Vandersteen to otherwise frequency optimized speakers, such as Magico, Monitor audio, Revel, my own DIY designs or Fritz speakers, I do not hear a benefit in the former to the latter. That doesn’t mean they don’t sound different, but the only differences I hear are easily attributable to the frequency and amplitude, not phase. Sorry in this manner I am like Toole and the participants in several studies that have not shown phase alone to be audible.

As for the brain, yeah, so I’m not phase sensitive now. I don’t want to be. I don’t want to be more sensitive to playback systems than I already am. :)

Best,

E
wolf_garcia
6,798 posts
 
Listening to any group playing acoustic instruments, or even a band with electric instruments that are not "sound reinforced" by a PA system, provides you with delays (in an orchestra there's nearly a city block between furthest left and right), phase anomalies, timing irregularities, and a different sonic mix experience for every person there. The only answer to these issues is to avoid live music at all costs or be forever led astray.
roberttdid
534 posts
 
I think what you are describing Mijostyn is not phase sensitivity but out of phase cancellation of two distinct sources. This is usually a worse issue when subs are colocated with the mains.
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