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If the study lacks scientific rigor because it used only 47 participants, then how many participants are enough? 470? 4,700? I would say that even a sample of 470,000 Americans would not be enough if the purpose is descriptive, because it does not represent Canadians, Mexicans, Brazilians, etc. etc. But, if the purpose is experimental, 47 participants are very good enough (provided other things are properly done).
+ Rep. This response is more educational, because it explains rather than simply throwing out jargon.
Still have a question though (sorry for the digression): If driver placement makes inaudible or at most minor difference (provided the configuration is not too off), what is the advantage of custom, then? I read you writing on Spyro's page that custom is better because "the extension on both ends is also much easier to feel/identify". How so?
Got it. Not April fool.
I take it you didn't read my
follow-up post to the '47 subjects is not enough' post... the thing to keep in mind is the goal and scope of a study, and whether the chosen subjects/methodology are suitable for testing the hypothesis in a rigorous manner. The goal of the study was to evaluate whether measured mannikin responses correlated well with the measured responses of real human ears (with in-ear microphones). This type of study requires constant reevaluation to include an ever larger and all-encompassing population of test subjects. For pure scientific pursuit, it would be interesting to see which ear/pinnna simulators are more suitable for which populations. In the clinical setting, I see patients with all sorts of different types of ear shapes and with a variety of conditions. To be defined as having hearing loss, 'deaf' people don't just have sensorineural hearing loss of the inner ear, or conductive hearing loss of the ear canal/ossicles/etc. Patients with malformed pinnae can also be classified as hearing disabled. There are people with microtia (very small ears) that can have problems with proper hearing because of the, but they have perfectly fine sensorineural hearing (although most do have problems with the entire ear, since it is a congenital malformation), thus it may be important for the hearing aid they fit to have normal diffuse field equalized response. So, do they want to hear things like the typical Caucasian, or Asian, or any other ethnicity? While I'm sure these responses are extremely close to each other (we are the same species, after all), there will be population differences.
Again, this discussion really isn't important to the true topic at hand. In fact, the question of whether customs are better is also not really relevant to the 'why not a dual BA from Etymotic' discussion.
But to answer your question, I wouldn't say that driver placement makes an 'inaudible or at most minor difference' --- these small differences add up. A TWFK placed at the very front of the shell sounds quite different from one placed at the back of the shell, but they're not differences that you would immediately hear. They're most apparent in the harmonics, and certain other peaks that may be absorbed by the long length of the sound tube.
I don't remember writing on Spyro's page, but I do agree with that statement. I would say the biggest difference is perceived isolation. There may be advantages in terms of circuit design enabling drivers' performance, but I can't be sure of what those advantages are at the moment, so I don't want to comment.
