The second version of the iOS beta includes support for the iPad, the Los Angeles Times reported.
When Apple unveiled iOS 7 this month and first made it available to developers, the first release of the upcoming operating system worked only for the iPhone and the iPod Touch.
The new voices for Siri, now available in either male or female choices, have been developed to sound less robotic, Apple said.
In addition to the new voices, the latest beta version features an overhauled Reminders app, the return of Voice Memo, and a number of other small improvements.
Apple is expected to release iOS 7 to the public this fall in conjunction with the unveiling of its next-generation iPhone.