Thanks for the replies.
raindoctor“
Due to assimilation, One can produce MPR instead of NPR;one can hear MPR Another example: " S n P" is heard as SMP, and is produced as SMP instead of SNP.
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By the way, raindoctor, are you a native speaker with "native ears"? From North America, the UK, where? If you are not willing to tell it, forget these couple of lines.
Anyway, I'll go straight to the point. What I'm trying to find out is how sensitive native speakers' ears are when assimilation of this kind is involved.
I learned such kinds of assimilation are not automatic in English, unlike in Italian (In Italian, "un pesce" would always be pronounced "um pesce"). As far as I know, in English it isn't automatic (it is more likely in certain dialects, and the faster the speech, the more likely the assimilation), and the assimilation can be partial.
So production can vary from non assimilated (the tongue moves all the way up to form the /n/) to assimilated (the tongue doesn't even move and you go straight to the bilabial sound)... but production and perception are separated concepts, I guess. If production varies, how does perception vary?
Which boils down to the question: while native speakers can easily produce both non-assimilated NPR and MPR, can they also easily distinguish them?
I think (but I'm not sure at all) that maybe I would only be able to distinguish /np, nb, nm/ from /mp, mb, mm/ in very slow careful speech, and the difference would still be too small for me to consider it "phonemically" important. But it's hard to say how well native speakers understand: they usually guess from the context, using a kind of top-down noise reduction (from context and words down to phonemes). Yet natives' ears must be very sensitive anyway, because they can easily detect traces of accents that are either foreign or different from their own.
So I decided to try to understand more about English speakers' ears with some little experiments. I recorded some audio clips from both NPR (National Public Radio) and MPR (Minnesota Public Radio). Then I chose one, it's simple and in high quality for voice (128 kb/s).
And so we simply need to consider one question... Can native speakers tell if that's Minnesota Public Radio or if it's National Public Radio, and how sure are they about their choice?
That's all. Keep placing your bets guys! You might win something, LOL. 