Google on Monday confirmed what the blogosphere has suspected for the past week: It has acquired GrandCentral Communications, an online voice communications management startup. The terms of the deal were not disclosed. The deal marks Google's twelfth acquisition so far this year. In 2006, Google made only 8 acquisitions.

"GrandCentral is an innovative service that lets users integrate all of their existing phone numbers and voice mailboxes into one account, which can be accessed from the web," said Google product manager Wesley Chan in a blog post on Monday. "We think GrandCentral's technology fits well into Google's efforts to provide services that enhance the collaborative exchange of information between our users."

As a consequence of its acquisition by Google, GrandCentral is no longer accepting new users.

"Our priority now is to ensure that our current beta users continue to have a great user experience," explained GrandCentral co-founders Craig Walker and Vincent Paquet in a blog post. "While we scale the service, we are moving to an invitation-only model for new users."

Those interested in trying GrandCentral can sign up for an invitation to join the service once Google has GrandCentral running on Google infrastructure.

The deal will result in one notable change for GrandCentral users: No longer will users be able to upload their own ring back tones. Instead, GrandCentral users "will be able to choose from a selection of licensed sound files made available within the GrandCentral service."

Presumably, Google is eager to avoid copyright issues surrounding user submitted music and to assure potential mobile phone partners that Google isn't a threat to their ring tone business.

Google has reportedly been working on its own mobile phone with Taiwanese phone manufacturer HTC and European telecom company Orange. It is also providing software and services for Apple's iPhone.