We have already seen how to change the reminder sound in Outlook 2010 using Outlook options. Similarly outlook options can be used to disable or turn off the outlook reminder sound.
Click the File menu –> options link and select Advanced tab. In Advanced options navigate to Reminders section.
By un marking the checkbox with label as Play reminder sound, you can turn off the reminder sound in Outlook 2010 After making this change, click the OK button to save the changes.