[sdiy] Cpacitor whine

[flightofharmony at comcast.net]

Whee! Here's another one: (still) Building an AD EG with a 555, everything functions great both when triggered and set to repeat. The only problem left is that there is a capacitor charging whine when triggered. I'm going to try swapping caps and see what that does. I was wondering, what are  the main causes of that whine (apart from the capacitor charging)? What are the best ways to avoid this in the future?

Also, much thanks and appreciation for all the helpful responses that I have received in the past - I often forget to say that when troubleshooting.

~flight