You'll find one in the Custom Sounds Forum. Some are full sound packages, some are only sounds for individual items. I started with Mitzu's sounds back in the dark ages, and have morphed and added to it over the years. I'm currently using a hodge-podge mix of sounds.
It's up to you to pick one. Preferences vary. You'll only know if you like it by trying it out. I'm on 28K dial-up, and they take me many hours to download. I don't do that very often...
Pick one. Download it. It'll probably be "zipped", so unzip it. I do this in "My Documents". Rename the folder as "sounds". That's very important. AH will only recognize a sounds folder if it is named "sounds". Leave it in "My Documents" for now.
Find your AH folder. The path to find mine is- My Computer- Local Disk "C"- Program files- HTC- Aces High II. Open Aces High II, and look for the folder named "sounds". !!BEFORE!! you move the new sounds folder into your AH folder, re-name the original folder to something else. I renamed mine "sounds1". If you replace the original, it will be gone forever, so don't replace it, rename it...
As soon as it is renamed AH will no longer recognize it, and you've effectively removed all sounds from the game (except vox? maybe?).
Now you can leave that folder in your AH folder, and if you ever want the default sounds back you'll have them (by renaming them "sounds" again).
Now, go back to your new sounds folder, and move it into the Aces High II folder. You'll be moving one big folder around, full of smaller folders. Don't try to move the individual effects or aircraft files or folders around.
The new "sounds" folder will be recognized by AH as the one to use.
MtnMan