SAN FRANCISCO – In its first product unveiling since Steve Jobs resigned as CEO, Apple on Tuesday introduced a faster iPhone with voice features and a higher-resolution camera to help it compete with Google’s Android.

The A5 chip in the new iPhone 4S will be seven times faster than the old processor, Apple said Tuesday at its headquarters in Cupertino, Calif. The model will cost $199, $299 and $399, depending on features, and will be sold by Sprint Nextel for the first time. Apple already has agreements with AT&T and Verizon Wireless.

The update of Apple’s best-selling product marks an early test for Tim Cook, CEO since Aug. 24, who hasn’t yet shown he can match his predecessor’s skills at product design and marketing.

While the iPhone is the world’s most popular smartphone, Google’s Android software is more widely used, showing up in devices from Samsung Electronics and HTC Corp. Shares slumped Tuesday during the presentation after Apple failed to announce a more groundbreaking iPhone 5 model.

“There is some disappointment that only one new iPhone has been announced,” said Shaw Wu, an analyst at Birmingham, Ala.-based Sterne Agee.

The 56-year-old Jobs, who remains Apple’s chairman, didn’t appear at the event Tuesday. He has taken three medical leaves over the past seven years amid a battle with a rare form of cancer.

The iPhone 4S, available Oct. 14, will have a camera with 60 percent more pixels and can handle high-definition video. The device also relies on an “intelligent antenna system” that’s designed to improve call quality and works with both CDMA and GSM wireless standards. Users will have up to eight hours of talk time on one charge.

“For many customers, the iPhone 4S will be the best still camera they’ve ever owned, the best video camera they’ve ever owned, and it’s with them all the time,” said Phil Schiller, a senior vice president in charge of product marketing.

A new voice-recognition system, meanwhile, will turn the device into a hands-free personal assistant.

The technology lets users check weather, get directions or surf the Web using speech commands. Apple already had basic voice-control abilities on the iPhone for placing a call or accessing a song.

Apple acquired a speech-recognition software company last year called Siri, which helped it develop the new features. The system relies on artificial intelligence to handle users’ questions.

Scott Forstall, a senior vice president in charge of iPhone software, demonstrated the technology on stage by asking the phone, “Who are you?”

It responded, “I am a humble personal assistant.”

The features, combined with the more aggressive prices, will give Apple an edge, said Andy Hargreaves, an analyst at Pacific Crest Securities in Portland, Ore.

“Siri is very unique from what I’ve seen and should continue to differentiate them at the high end,” he said.

The older iPhone 4 model will now cost $99, and the iPhone 3GS will be free with a wireless contract, Apple said.