If you know the length of the sound file, then you can use a timer to start the sound each time.
Something like:
B4X:
Sub Globals
End Sub
Sub App_Start
Form1.Show
timer1.Interval = SOUND_LENGTH_IN_MILLISECONDS
End Sub
Sub btnStart_Click
timer1.Enabled = True
End Sub
Sub btnStop_Click
timer1.Enabled = False
End Sub
Sub Timer1_Tick
Sound("sound.wav")
End Sub