Atc Sound And Overspeed Warning Problems

[ngatimozart]

Hi, I run FSX Acceleration with a Windows 7 OS on a Quad Core 3.2Ghz CPU and 8GB RAM. I am running a NVIDA GeForce 9600 Video card. I have lost the ATC sound and the overspeed warning both sound and visual. Methinks I have turned it off inadvertently but cannot find ay of turning it back on. Any help or advice would be greatly appreciated. Thanks.