Alerts and sounds doesn't work in safari

Hello,

There are several web apps that launch javascript alerts and sounds to inform the user about updates or any information. I use at least 2 websites daily and they are completely relevant to perform my job. a clear example is a web chat. If I'm not in the chat tab I'm not alerted (sound & javascript alert) when a client is asking for help (which is so in firefox, chrome and even the obsolete Internet Explorer for Windows 🙂)

** I have just one year using MAC and I think is an incredibly & flexible system, but I'm starting with Safari.

Thanks for your help!