EB on Android with RS 6000, decodeVolume not working


I use the Enterprise Browser 2.0 on a TC52 with Android 8.1. The application is HTML with Javascript.

I try to disable the sound on a good decode while barcode scanning, because I use EB.Notification.beep, so that I can contro, the beep.

I tried several codes:

scanner.decodeVolume = "0";
scanner.decodeVolume = 0;
scanner.setProperty("decodeVolume", 0);

But the scanner still makes its won beep.

Has somebody has a idea what I'm making wrong?