Google Calendar currently does not have a sound reminder. There is a pop-up based on the reminder set in the calendar.
GMinder is a program which can manage multiple calendars and triggers a sound alert before an appointment as a reminder. This program sits quietly in your system tray and prompts you for an appointment based on the settings you create in the program. It syncs with your Google Calendar and keeps you up to date. Try it to see how it works in your workflow.