Grammar question regarding acronyms

Here’s something I’ve wondered about for a while now. Say you’re writing a sentence with an acronym in it. Say that acronym spells a word, like HALO (High Altitude Low Opening). Since HALO, when pronounced halo, starts with a consonant, do you put a single “a” in front? Or do you put an “an” in front because when you say H-A-L-O it has a vowel sound in the front?

Which is correct?

  1. I’m going to do a HALO jump! (pronounced halo)

  2. I’m going to do an HALO jump! (pronounced H,A,L,O)

This might not be a good example since HALO might be commonly referred to as halo, but you can imagine having a new, less commonly used acronym that could be put in instead.

The key is sounds, not letters. If “HALO” starts with a vowel sound then use “an.” If it starts with a consonant sound then use “a.”

Thus, both of your examples are correct. It all depends on how you are pronouncing “HALO.”

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Worst. Coding. EVAR!

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Ah, thanks. I figured that the sound was probably it, but it’s always good to know for sure.