stop audible alert of new email

Firefox doesn't do email, nor does Firefox have a sound for new email. Have you installed an add-on for webmail alerts? ----- Do you have that problem when running in the Firefox SafeMode? <br /> [http://support.mozilla.com/en-US/kb/Safe+Mode] <br /> ''Don't select anything right now, just use "Continue in SafeMode."'' When in Safe Mode... <br /> * The status of plug-ins is not affected. * Custom preferences are not affected. * All extensions are disabled. * The default theme is used, without a persona. * userChrome.css and userContent.css are ignored. * The default toolbar layout is used. * The JIT Javascript compiler is disabled. * Hardware acceleration is disabled. If not, see this: <br /> [https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems]