You'll have to either switch to an action-based loop(which is a lot easier in newer versions of VoiceAttack as you can use a For loop to specify the repeat count), or use a variable to keep track of the repeat iterations with a condition that plays a sound when that variable reaches a certain value.
Option A:
Start Loop : Repeat 10 Times
Write '[Blue] This will execute 10 times' to log
End Loop
Play sound, 'C:\Windows\Media\ding.wav'
Option B:
Write '[Blue] This command also executes 10 times, using the "This command repeats" option' to log
Set integer [~repeatCount] to [~repeatCount] plus 1
Begin Integer Compare : [~repeatCount] Equals 10
Play sound, 'C:\Windows\Media\ding.wav'
End Condition
The "~" character prefixed to the variable name denotes a command-scoped variable, meaning it is always "Not Set" when the command starts, and can be different when running multiple instances of the same command simultaneously(so one command instance won't affect the other).