Obviousness

Based on my analysis of U.S. Patent No. 9,203,972 and the cited prior art, several of the patent's claims appear vulnerable to an obviousness challenge under 35 U.S.C. § 103. A person having ordinary skill in the art (PHOSITA) in audio signal processing at the time of the invention (with a priority date of October 1, 2007) would have been motivated to combine existing technologies to achieve the claimed invention for predictable reasons, primarily to reduce computational complexity.

The core innovation of US 9,203,972 is not merely processing audio in sub-bands, but rather the three-step process of excising some sub-bands to save computational resources, processing the remaining sub-bands, and then reconstructing the excised ones before final synthesis. This approach seeks to balance processing efficiency with acceptable audio quality.

Combination of Prior Art for Obviousness

A strong obviousness argument can be constructed by combining a primary reference that teaches sub-band audio processing with a secondary reference that teaches the reconstruction of missing audio data.

• Primary Reference: US 5,272,695A (hereafter '2695), titled "Subband echo canceller with adjustable coefficients using a series of step sizes." This patent, cited by the '972 examiner, clearly discloses a system for acoustic echo cancellation that operates in the sub-band domain. It teaches splitting a microphone signal and a reference (loudspeaker) signal into multiple frequency sub-bands and using adaptive filters on each sub-band to cancel echo. This establishes the foundational framework for sub-band echo cancellation. However, '2695 appears to process all sub-bands, which is computationally intensive.

• Secondary Reference: US 2011/0142257 A1 (hereafter Goodwin), titled "Reparation of Corrupted Audio Signals." This reference addresses the problem of missing data in an audio stream (e.g., due to packet loss). It teaches various methods for reconstructing, or "repairing," the missing segments by using the information from surrounding, valid audio segments. The techniques disclosed include interpolation and other estimation methods.

Obviousness Analysis of Independent Claims

Claim 1 & Claim 13 (Method and System for Echo Cancellation with Excising/Reconstruction)

• Claim Language: These claims cover the method and system of dividing both a microphone signal and a reference signal into sub-bands, excising a corresponding number of sub-bands from each, processing the remainder for echo cancellation, and then reconstructing the excised microphone sub-bands.
• Obviousness Argument:
  1. Starting Point ('2695): A PHOSITA begins with the sub-band echo canceller taught by '2695.
  2. Known Problem: As stated in the '972 patent's own background, a key problem in the field was that such processing "may be computationally complex. For example, memory demand and computation time may be relatively high for these processes." (US 9,203,972, Col. 1, ll. 24-27). A PHOSITA would be motivated to reduce this complexity.
  3. Obvious Solution Path: A common and obvious way to reduce computational load in multi-channel or sub-band systems is to simply process fewer channels or bands. A PHOSITA would recognize that not all frequency bands contribute equally to echo or speech quality and would be motivated to discard (excise) some bands (e.g., every other band, or bands in less critical frequency ranges) before the computationally expensive adaptive filtering step. This is a standard engineering trade-off of performance versus cost.
  4. New Problem & Motivation to Combine: Excising sub-bands solves the complexity problem but creates a new problem: how to re-create a full-band signal for output without introducing audible artifacts. To solve this, the PHOSITA would naturally turn to the established art of repairing or reconstructing missing audio data. Goodwin provides an explicit solution, teaching how to fill in missing audio segments by using information from adjacent valid segments.
  5. Conclusion: It would have been obvious to a PHOSITA to modify the system of '2695 by intentionally excising certain sub-bands before echo cancellation to save processing power, and then applying the known signal reparation techniques of Goodwin to reconstruct the excised sub-bands to create a complete output signal. The combination would result in the system and method described in claims 1 and 13.

Claim 6 & Claim 12 (Method and System with Reconstruction by Interpolation)

• Claim Language: These claims specify that the reconstruction of an excised sub-band is performed by interpolation using remaining sub-band signals from the same time and adjacent times.
• Obviousness Argument: The argument follows the same logic as for Claim 1, but with a more specific teaching from the secondary reference. Goodwin explicitly suggests interpolation as a method for signal repair. Therefore, once a PHOSITA is motivated to combine '2695 with a signal reparation technique, choosing interpolation—a specific method taught by Goodwin for that exact purpose—would be an obvious design choice, not an inventive step. This renders the specific reconstruction method of claims 6 and 12 obvious.

Claim 5 & Claim 8 (Method and System with Reconstruction by Averaging)

• Claim Language: These claims specify reconstruction by averaging enhanced sub-band signals.
• Obviousness Argument: Averaging is one of the simplest forms of interpolation. The motivation to excise bands ('2695 + desire for efficiency) and then reconstruct them (the problem solved by Goodwin) remains the same. A PHOSITA, considering the interpolation techniques taught by Goodwin, would recognize averaging as a computationally simple and well-known implementation of that principle. Selecting averaging would be a routine design choice, not a patentable invention. Therefore, claims 5 and 8 would have been obvious over '2695 in view of Goodwin.