i have found the file in
windows\system32 , G:\GAMES\Rail Simulator
and there is no openal32.dll in ArmA directory
windows\system32
properties are
openal32.dll 6.14.462.0
Standard OpenAL Implementation
Copyright© 2000-2005 NVIDIA Corporation
(external Hard Drive)
G:\GAMES\Rail Simulator
properties are
openal32.dll 2.1.8.1
Creative Labs OpenAL32
Copyright © 2007