Is Siri’s Absence on the iPhone 4 Due to Lack of Noise Reduction Circuitry?

When the iPhone 4S debuted with Siri, many iPhone 4 owners pondered why they weren’t able to have access to the voice recognition technology. Sure, there are unofficial ways to acquire Siri on your iPhone 4, but what is the real reason behind its absence?

CNET reports the main reason the iPhone 4 was left out was due to the absence of a particular “EarSmart” noise reduction technology in the A4 chip that powers the device, whereas the larger A5 processor does, as revealed in tear downs by iFixit. The company behind this technology is called Audience, and their recent IPO revealed a partnership with Apple:

The details answered a question that Linley Group analyst Linley Gwennap had about the A5 chip that powers the iPhone 4S: why is it so big? Larger processors are more expensive and can consume more power, and chip designers strive to trim every last square millimeter from their designs.

“Even after accounting for the dual Cortex-A9 CPUs and the large GPU that provides the A5 with industry-leading 3D graphics performance, the remaining die area seems too large for the usual mundane housekeeping logic,” Gwennap said in a report yesterday. “To reduce system cost and eliminate the extra package required for the Audience chip, Apple cut a deal to integrate the noise-reduction technology directly into its A5 processor, which appears in the iPhone 4S.”

Audience describes their earSmart technology as:

earSmart™ is an intelligent voice processor that delivers a clear voice and audio experience for mobile devices, allowing you to hear and be heard™ even in noisy settings. Our earSmart Advanced Voice processors use the science of human hearing to distinguish sounds, instinctively enhance voice quality and suppress surrounding noise, for radically clear conversations just about anywhere.

Below is a promotional video by Audience for their earSmart technology, which is also used in over 50 smartphones by numerous companies:

Essentially, the argument is that ‘EarSmart’ technology allows Siri to perform significantly better in noisy environments, and being built into the A5 chip means it’s only available for the iPhone 4S, instead of the iPhone 4. The technology works quite well, as Siri is still effective in relatively noisy situations, based on our tests over the past few months.

What do you think? Is this the reason why Siri is exclusive to the iPhone 4S? Are the dual microphones on the iPhone 4 not good enough for Siri?