I have a two part answer to make sure I cover this subject for future visitors to this FAQ.
The first part is that I have tested and found it is not possible to get this indicator to trigger an audible alert on a chart. The reason it does not work is likely the result of how it was written. (details in the second part of my answer below). Of course I don’t have access to the source code so I cannot confirm. But the fact you can’t get this thing to trigger an audible alert leads me to believe it was constructed in a way that makes the alerts fail to function.
I can tell you from experience you are not likely to get the results you seek. The scalper alert is programmed to look 2-3 bars forward, only changing the color of the bar once the signal is confirmed 2-3 bars later. So you can never check if the scalper alert triggered in the previous bar. Now, perhaps you can check if scalper alert triggered 4 bars back. But by then the price has moved and you loose the advantage of an early entry you are seeking. The Scalper alert looks like it gives perfect signals that make lots of profit. But because of the 2-3 bar delay in confirming the signal, it can never be traded on a live chart.
A few more details:
This also means you can not use this indicator in a Study Alert. How about a Scan? I haven’t tried that yet. If you are interested in the answer, post a question and I’ll investigate.