Auto "Beep" sound doesn't work

Dears,

Here is my VBA to make "Beep" sound when "a1" cell is =1, it can work when i put 1 into "a1" cell manually, but it doesn't work when run with macro. Pls help!!

byron

Private Sub Worksheet_Change(ByVal Target As Range)
If Range("a1") = 1 Then
Application.Wait (Now + TimeValue("0:00:01"))
Beep
Application.Wait (Now + TimeValue("0:00:01"))
Beep
End If

End Sub