Please help me with these ARTICLES
I was doing my exercise and bumped into the following sentences:
1. AN NBC news program is going to be changed following the advice of the reviewers.
2. They are developing A one-hour program that may interest older viewers.
How confused I am because I have always thought that AN is followed by a word starting with a vowel, but here in this case, it is followed by "NBC", which starts with an "N"
Similarly, a is followed by a word that begins with a consonant, but here in this case, it is followed by "one-hour".
Could you please explain these cases and copy a link that talks intensively about this phenomenon for me?

Question

Answer

broadly speaking, those are the rules, but in fact, if the first letter of the word SOUNDS like a vowel then we treat it as one, and if it sounds like a consonant, then we treat it as one for the purpose of deciding whether to put a or an in front.
So the "N" of NBC is pronounced 'en" - sounds like 'e' a vowel
One starts with a vowel, but that vowel is pronounced like a 'w' - 'won'.
Is that clear??

Answer

Hilary summed it up nicely. It's not really a "phenomenon", just the normal use of 'a' and 'an'. Remember, it's the sound that counts, not the spelling.