Many have wondered why Siri is only on the iPhone 4S, and some think it’s just to force people to upgrade to use Siri. It turns out that it’s much more than that with Apple integrating all kinds of circuitry for Siri to live up to their extremely high standards. The start-up company, Audience, revealed their Apple partnership in their initial public offering (IPO), and now the details have been revealed (via Cnet). During the initial tear downs of the 4S, it was discovered the A5 chip was bigger than would be needed for the actual chip, and the extra space was a mystery.

The mystery has been solved as the Audience partnership details have emerged, and it shows that their EarSmart technology is built right into the A5 chip. The iPhone 4 features a separate dedicated Audience chip, while the 4S has the circuitry built into the A5 with a whole new technology too. Apple had to cut a royalties deal with Audience for the noise reduction technology to be built directly into the A5 chip, and it makes all the difference.

Audience also explained that the Audience chip in the iPhone 4 was their first generation, and is only useful when the phone was held to the speaker’s mouth. The second generation built into the A5 chip can handle “far-field speech” which allows the noise reduction technology to work when the phone is at arm’s length. Most Apple ads show the iPhone being held in front of users, and that’s the main reason why Siri won’t come to the iPhone 4 as a software update.

Audience also has a third generation noise reduction technology on the way, and Apple is already a licensee though no details could be provided. It could be directly built into the A6 for the iPad 3, but there was no word if the same A5 chip is used in the iPad 2 as the iPhone 4S. As for how EarSmart works,

Imitating the complex processing that occurs from the inner ear to the brain, Audience’s intelligent EarSmart technology distinguishes and interprets sounds as people do naturally…In a mobile device, the earSmart processor effectively isolates and enhances the primary voice signal and suppresses surrounding noise–for both transmit and receive.”

The main goal is to work when people hold their phones further away including with Siri, video conferencing, hands free calls in the car, and other similar situations. A noisy environment is when you’ll notice the difference, and it all goes back to Apple making sure that Siri lives up to their very high standards. A jailbreak, illegal proxy server, and hack can bring Siri to the iPhone 4, but it won’t work like the 4S, and Apple doesn’t think the experience is good enough. If you ever wonder again why Siri is an iPhone 4S exclusive, it’s all in the chip.