SpeechSynthesizer Registry keys for RegistryPermission

Question

how do I find out the registry keys, which the SpeechSynthesizer is using. I need to add them with RegistryPermission so I can use SpeechSynthesizer again.

I denied in my own appdomain every access as standard and added the following ones so I think I need only the RegistryPermission but I have no clue how to get them.

var grants = new PermissionSet(PermissionState.None);
grants.AddPermission(new SecurityPermission(SecurityPermissionFlag.Execution));
grants.AddPermission(new SecurityPermission(SecurityPermissionFlag.SerializationFormatter));
grants.AddPermission(new SecurityPermission(SecurityPermissionFlag.Infrastructure));        
grants.AddPermission(new EnvironmentPermission(EnvironmentPermissionAccess.Read, "USERNAME"));
grants.AddPermission(new FileIOPermission(FileIOPermissionAccess.AllAccess, Assembly.GetExecutingAssembly().Location));
grants.AddPermission(new ReflectionPermission(PermissionState.Unrestricted));                
grants.AddPermission(new UIPermission(PermissionState.Unrestricted));

Thanks in advance.