SoundCloud announced that it has hit the 10 million user milestone. That’s registered users, by the way. You don’t have to be registered to listen to sounds. Over 7 million of those users have come over the past year.

It looks like mobile has been a pretty big factor. While a spokesperson for the company tells us it isn’t breaking out the iPhone vs. Android app numbers yet, the company does say that its mobile apps have been downloaded over 5 million times.

Furthermore, over 10,000 apps are being developed on SoundCloud’s open platform. Recent additions include integrations with pro music creation software Pro Tools and Cakewalk.

“As we continue to work hard to innovate on our platform and API, it’s the support and creativity of our community that motivate and inspire us every day,” says co-founder and CTO Eric Wahlforss.

CEO Alexander Ljung adds, “When Eric and I started SoundCloud, we had the vision of enabling people to create and share sound more easily and collaboratively. Today 10 million people are recognizing that vision and it makes us extremely proud and encouraged that people are supporting our mission to unmute the web.”

To celebrate the milestone, SoundCloud has created a new SoundCloud Labs project called Story Wheel, which enables users to record a narrative around a series of images “to tell a personal story”.

You can see an example from Ljung and Wahlforss here.

“New projects like ‘Story Wheel’ demonstrate how placing sound as the central component of an online experience can be incredibly powerful,” says Wahlforss.

The company points out that SoundCloud is about much more than music, noting that journalists, bloggers, publishers and educational institutions are also among those taking advantage.

Earlier this month, SoundCloud announced that it has raised an undisclosed amount of funding led by Kleiner Perkins Caufield & Byers, which the company says will allow SoundCloud to continue to expand more rapidly.