From the archives...
The following question was originally posted on the (now discontinued) LOE Forum.
I know the 3 sounds for the phonogram A - but am not clear on how to explain where the more nasal sound of "a" is coming from in an/and/can.
That is a great question. First, as a bit of background: In English - and in human speech generally - the way we form sounds in our mouths actually varies depending on what other sounds are around them in words. This is called assimilation.
Most of the time the variations are so subtle that we don't even notice we are making them and easily categorize the two versions of the sound as one phoneme. (A phoneme is a speech sound.) They are just slight shifts that make the sound easier to pronounce in the context of that word. However, certain sounds shift more than others, and often they shift more in some English-speaking dialects than others.
The short /ă/ in words like 'and,' 'man,' and 'can' is a good example of this: in some parts of the English-speaking world this sound is very similar to the short /ă/ in 'mat,' 'apple,' or 'snack,' but in much of the US it gets distorted significantly before the nasal /n/ sound. For many US speakers something similar happens before the nasal sound /m/, as in 'ham,' 'cram,' etc. The shift in the vowel is even greater before /ng/ sounds in some parts of the US; some people hear the vowel in the words 'thank' and 'sang' a long /ā/.
If you feel where in your mouth you form your /ă/ and where you form the nasal consonants /m/ and /n/, you may be able to get a sense of why this happens.
I don't know this for sure, but I wonder if the reason that the short /ă/ gets more distorted in US English than in most UK English speakers' pronunciation is that our short /ă/ sound is already closer in our mouth to where the nasal consonants are formed - a little wider, a little further back. Perhaps when this vowel sound is closer in the mouth to these consonants, there's more of a tendency for the shape of the consonants to influence how we say it.