Sound cannot be disabled on remote desktop connections through the Remote Web Workplace.
Cause: The Hear sounds from the remote computer on this computer option on the computer selection page cannot be disabled until the Remote Web Workplace Web site is added to the trusted sites zone in Internet Explorer. By default, sound will be played.
Solution: Add the Remote Web Workplace to the trusted sites zone in Internet Explorer.
To add the Remote Web Workplace to the trusted sites zone in Internet Explorer
Click Start, and then click Internet Explorer.
On the Tools menu, click Internet Options.
On the Security tab, click Trusted sites, and then click Sites.
Under Add this Web site to the zone, type the URL for the Remote Web Workplace, and then click Add.
Click OK, and then click OK again.