VoodooVox, a New York start-up that provides advertising within phone calls, said it has raised $8.1 million in a fourth round of financing.It is led by Softbank Capital, and includes existing investors Apax Partners, Disney’s Steamboat Ventures, and Village Ventures, also participated in the round.

VoodooVox’s product is called “In-Call Media,” and it inserts ad-supported audio content into the calls of  large companies, mainly within customer service calls and the like.  The company says its technology is being used 300 million calls monthly, however that number referring to the call volume handled by its clients, and not necessarily to the number of calls where ads are actually placed.

The customers include calling card companies, 411 services, call centers, radio stations, VOIP providers, and various Voice 2.0 applications, the company says. These include IDT, Univision, Virgin Mobile, Nokia, Microsoft and Showtime.