The new version of Internet Explorer that was installed last week has the sounds turned off by default. To turn sounds back on in Internet Explorer:
Click on the “gear” icon in the upper right corner
From the menu that pops up, choose Internet Options.
On the next window that opens, click on the Advanced tab:
Scroll down to the Multimedia section and check the box for Play sounds in webpages.
An alternative to all of the above is to use another browser, such as Firefox or Chrome.