A method and system are disclosed for monitoring vacuum integrity in a vacuum interrupter. The method includes injecting sonic signals into a body and detecting sonic signals reflected from the body. A composite value is calculated from the reflected sonic signals and a determination made based on the composite value as to whether the vacuum is acceptable. The system includes the following components: a transducer for sending sonic signals into a body; a receiver for receiving sonic signals reflected from the body; a signal processor for calculating a composite value from the sonic signals reflected from the body; and a processing unit for determining from the composite value whether the body has an acceptable vacuum therein.