All of a suddenI,m getting noise from my longbow.You can hear that slap when you release the arrow.Changed the brace height and even tried a heavier arrow with no results.Want to fix it,Iknow deer will hear it.Anybody have any suggestions on what I can do???

If it was quiet before, what have you done differently to make it all of a sudden, noisy?  If you haven't changed anything prior to that, it is either a brace height issue or a release issue (probably).

Sounds like it was quiet and became noisy.  It sounds like something in your form changed.  Use a video camera and video your shooting to see if there is a form error.  If your arrows were right on the edge of proper spine a small form error can cause the shaft to slap the riser during paradox.

I often get a slap sound out of my longbows if I don't put even pressure on my fingers.  I have a bad habit of putting more pressure on my third finger and it causes a slap everytime.  May not be your problem, but it won't hurt to experiment.

Fletching clearance issues off the shelf?

What's changed??????? If it was silent and now it's not, something is different. You have to go into your detective mode and find the culprit!!!!!

Many times a new string will solve the problem.  Strings tend to get noisier after they have been shot for  long time.