Prior art

Analysis of Prior Art for U.S. Patent No. 9,203,972

The following analysis details the most relevant prior art cited against U.S. Patent No. 9,203,972, which pertains to "Efficient audio signal processing in the sub-band regime." The core invention of the '972 patent is a method for enhancing an audio signal by dividing it into sub-band signals, excising some of these sub-bands to reduce computational load, processing the remaining sub-bands to remove noise or echo, and then reconstructing the excised sub-bands to form an enhanced full-band audio signal.

The analysis below examines key prior art references cited in the '972 patent's file history. Each reference is assessed for its potential to anticipate the claimed invention under 35 U.S.C. § 102.

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Key Prior Art and Potential Anticipation of Claims:

1. U.S. Patent No. 5,272,695

• Full Citation: US Patent 5,272,695, "Subband echo canceller with adjustable coefficients using a series of step sizes."
• Publication Date: December 21, 1993
• Filing Date: September 14, 1990
• Description: This patent discloses a sub-band echo canceller that processes a signal by dividing it into multiple frequency sub-bands. It focuses on adapting the filter coefficients in each sub-band to cancel echoes. A key aspect is the use of different step sizes for adjusting the coefficients to improve convergence speed.
• Potential Anticipation of Claims: This reference is relevant to the general concept of sub-band processing for echo cancellation. It potentially anticipates the foundational elements of Claim 1, specifically the steps of "dividing a microphone signal into microphone sub-band signals" and "processing the remaining microphone sub-band signals by attenuating... echo components." However, the '695 patent does not appear to explicitly teach or suggest the novel steps of excising a predetermined number of sub-band signals to improve efficiency and subsequently reconstructing them. Therefore, while it provides a strong foundation for sub-band echo cancellation, it likely does not fully anticipate the complete method claimed in the '972 patent.

2. U.S. Patent No. 7,668,319

• Full Citation: US Patent 7,668,319, "Signal processing system, signal processing apparatus and method, recording medium, and program."
• Publication Date: February 23, 2010
• Filing Date: September 12, 2002
• Description: This patent describes a signal processing system that separates a signal into frequency bands and then processes these bands. The processing can include noise reduction. A significant feature is the synthesis of the processed bands back into a single output signal.
• Potential Anticipation of Claims: The '319 patent describes the core concepts of dividing a signal into sub-bands, processing them for noise reduction, and synthesizing them. This aligns with several steps in the claims of the '972 patent. However, similar to the '695 patent, the critical steps of intentionally excising sub-bands and then reconstructing them from the remaining processed sub-bands do not appear to be a feature of this invention. The '319 patent seems to process all sub-bands, which contrasts with the '972 patent's approach of selective processing for efficiency. This makes a direct anticipation of claims like Claim 1, Claim 8, and Claim 12 unlikely.

3. U.S. Patent Application Publication No. 2008/0159551

• Full Citation: US Patent Application Publication No. 2008/0159551, "System and Method for Acoustic Echo Removal (AER)."
• Publication Date: July 3, 2008
• Filing Date: December 28, 2006
• Description: This application details a system for acoustic echo removal that operates in the frequency domain, which is analogous to sub-band processing. It describes transforming the microphone and reference signals into the frequency domain, performing echo cancellation, and then transforming the signal back to the time domain.
• Potential Anticipation of Claims: This reference is highly relevant as it describes a modern approach to echo cancellation using frequency-domain techniques. It teaches dividing a signal into frequency components (sub-bands), processing these components to remove echo, and then reconstructing the full signal. This process is functionally similar to the steps outlined in Claim 1 and Claim 13. The key distinguishing factor would be whether the '551 application explicitly discloses the excision of certain frequency bins (sub-bands) from the processing path for computational savings and their subsequent reconstruction. If this specific efficiency-driven excision and reconstruction is not present, the '551 application would not fully anticipate the '972 patent's claims.

4. U.S. Patent Application Publication No. 2011/0142257

• Full Citation: US Patent Application Publication No. 2011/0142257, "Reparation of Corrupted Audio Signals."
• Publication Date: June 16, 2011
• Filing Date: June 29, 2009
• Description: This application focuses on repairing audio signals that have been corrupted, for example, by packet loss in a communication network. It describes methods for estimating and replacing missing segments of an audio signal by analyzing the characteristics of the surrounding, uncorrupted signal portions. This involves techniques like interpolation.
• Potential Anticipation of Claims: This reference is particularly relevant to the reconstruction aspect of the '972 patent's claims. Specifically, Claim 5, Claim 6, Claim 8, and Claim 12 describe reconstructing excised sub-band signals by averaging or interpolating adjacent sub-band signals. The '257 application teaches similar reconstruction techniques, albeit for a different purpose (repairing corruption rather than filling in for intentionally excised data). An argument for anticipation could be made if the reconstruction methods taught are directly applicable to the scenario described in the '972 patent. However, the context is different; the '972 patent's novelty lies in the combination of intentional excision for efficiency with this type of reconstruction. The '257 application does not appear to disclose this combination.

5. U.S. Patent No. 9,076,455

• Full Citation: US Patent 9,076,455, "Temporal interpolation of adjacent spectra."
• Publication Date: July 7, 2015
• Filing Date: August 22, 2011
• Description: This patent, assigned to the same initial assignee as the '972 patent (Nuance Communications, Inc.), describes a method for temporal interpolation of audio spectra. This is used to generate intermediate spectra between existing ones, which can be useful in time-scaling or for other audio modifications.
• Potential Anticipation of Claims: Given that this patent originates from the same assignee and deals with spectral interpolation, it is highly relevant, particularly to the reconstruction claims. The methods described for interpolating spectra could be seen as directly teaching the reconstruction methods of Claim 6, Claim 7, and Claim 12. However, since the '455 patent was filed after the priority date of the '972 patent (October 1, 2007), it does not qualify as prior art against the '972 patent. It is, however, indicative of related work within the same organization.