Apple Inc. v. Andrea Electronics Corporation

Citation: Not availableDocket: 18-2382

Court: Court of Appeals for the Federal Circuit; February 6, 2020; Federal Appellate Court

Original Court Document: View Document

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Apple Inc. appeals decisions from the Patent Trial and Appeal Board (PTAB) regarding U.S. Patent No. 6,363,345, which pertains to digital audio processing. The case originated when Andrea Electronics Corp. sued Apple for patent infringement in September 2016. In response, Apple filed two inter partes review (IPR) petitions in January 2017, challenging the validity of claims 1–25 and 38–47 of the patent. The PTAB consolidated the IPRs, concluding that all claims except claims 4–11 and 39–47 in the first IPR and claims 6–9, 17–20, 24, and 47 in the second IPR were unpatentable based on the prior art presented.

The PTAB declined to consider certain arguments made by Apple in its reply brief for the first IPR, stating those arguments were new and untimely. In the second IPR, the Board favored Andrea's construction of the term "periodically," which influenced its analysis. Apple contests the Board's decision regarding claims 6–9 in both IPRs, asserting that the Board should have considered its late arguments and that those claims are unpatentable.

The Court found that the PTAB erred by not considering Apple's reply arguments in the first IPR. Consequently, it vacated the Board's decision in that case and remanded for further consideration. However, the Court affirmed the Board's conclusions regarding the claims in the second IPR, maintaining that the decisions made were correct. Additionally, the excerpt includes a brief explanation of the technology involved in digital audio processing, describing the representation of sound waves.

Amplitude and frequency are critical parameters in sound waves relevant to human hearing, with amplitude relating to volume and frequency to pitch. Music and speech consist of various frequencies, and when multiple notes are played together, their combined signal differs from a simple sine wave, forming a composite graph of individual sine waves. To analyze these frequencies, a Fourier transform is employed, converting the signal to the frequency domain, which facilitates easier manipulation of the sound. This process produces a histogram of frequency bins, indicating the magnitude of each frequency.

The ’345 patent describes a method and system for noise cancellation utilizing Fourier transforms and a technique called “spectral subtraction.” The system converts audio signals into the frequency domain and establishes thresholds for each frequency bin to differentiate background noise. It employs two minimum values—“future minimum” and “current minimum”—to determine these thresholds over predetermined time intervals. The future minimum is initialized at the onset of each interval and updated based on observed signal magnitudes. The current minimum is set based on the previous future minimum and then tracks the minimum signal value for the next interval. The final current minimum is used to calculate an adaptive threshold for spectral subtraction, which removes noise from the audio signal.

Claims 6–9 of the patent, under appeal, depend on earlier claims and outline an apparatus for noise cancellation, comprising an input for audio signals, a frequency spectrum generator for creating frequency bins, and a threshold detector for setting thresholds based on noise estimation and assessing frequency magnitudes against these thresholds.

Claim 4 of the ’345 patent specifies that a threshold detector sets the threshold for each frequency bin based on a current minimum value derived from a future minimum value of the corresponding frequency bin's magnitude. Claim 5 further clarifies that the future minimum value is determined as the minimum magnitude within a predetermined time period. Claims 6 through 9 depend on claim 5 and impose specific conditions on determining the current and future minimum values. Claim 6 states that the current minimum value is periodically set to the future minimum value. Claim 7 allows for the future minimum value to be replaced with the current magnitude value if it is greater. Claim 8 permits the current minimum value to be replaced with the current magnitude value under similar conditions. Claim 9 allows for the future minimum value to be periodically set to the current magnitude value.

Apple has filed two Inter Partes Review (IPR) petitions, the ’626 IPR and the ’627 IPR, challenging claims 1-25 and 38-47 of the ’345 patent, alleging that these claims would have been obvious or anticipated based on three prior art references. In the ’626 IPR, claims 6-9 are asserted to be obvious based on the works of Hirsch and Martin, while in the ’627 IPR, these claims are claimed to be anticipated by Helf or obvious over Helf and Martin. The three prior art references include: 

1. Rainer Martin's 1993 paper on estimating the instantaneous signal-to-noise ratio (SNR) of speech signals, which outlines an algorithm that includes estimating noise power and tracking signal power levels over defined sample windows.
2. H.G. Hirsch and C. Ehrlicher's 1995 work on noise estimation techniques for robust speech recognition, which describes algorithms that use adaptive thresholds for audio frequency bins to distinguish noise from speech without needing explicit speech pause detection.

Hirsch identifies Martin's approach as a method to address speech pause detection issues and estimate noise characteristics from previous segments of noisy speech. U.S. Patent No. 5,550,924, described by Helf, presents a system aimed at reducing background noise in audio signals using Fourier transforms to analyze frequency domains and estimate noise in each frequency bin. Helf employs two methods for noise estimation: a more accurate "stationary estimator" requiring one second of background noise, and a "running minimum estimator" that provides quicker but less accurate estimates in ten seconds. The latter method updates the noise estimate based on differences exceeding a threshold when certain conditions are met.

In the ’626 IPR petition, Apple contends that Martin’s algorithm incorporates the “current minimum” and “future minimum” necessary for claims 6–9 of the patent, asserting that a person of ordinary skill in the art would recognize its capability to track the noise signal's magnitude. Apple’s expert, Dr. Hochwald, supported this with data derived from a single sub-window scenario. Conversely, Andrea, the patent owner, argues that Martin fails to disclose a “future minimum,” using examples to illustrate this claim. Andrea's expert, Dr. Douglas, applied Martin’s algorithm with multiple sub-windows to support his analysis. Apple countered that Andrea mischaracterized Martin’s algorithm, asserting that with one sub-window, the current and future minimum values align, thereby fulfilling the requirement for a future minimum in the claims.

Apple contended that the Martin algorithm, even when applied under Andrea's "multiple-sub-windows" approach, teaches a future minimum without specifying the period for its calculation. In scenarios with monotonically increasing signals, Apple argued that Martin fulfills the claims. For non-monotonically increasing signals, Apple maintained that the claims allow calculating the future minimum over a specific data window or using a previous sub-window's minimum. Apple supported its position with a reply expert declaration, and although Andrea deposed Apple's expert again, she did not seek to file a sur-reply or strike any of Apple's submissions. During oral arguments, the Board questioned whether Apple's reply introduced new arguments not covered in the initial petition, to which Apple referenced its earlier petition addressing the Martin algorithm's noise floor estimation process.

In its ’627 IPR petition, Apple argued that Helf meets the "periodically" limitation of claims 6–9, which involve a current and future minimum set "periodically." Citing Webster's Dictionary, Apple defined "periodically" as occurring at regular intervals or from time to time, asserting both definitions apply to the ’345 patent. Apple claimed Helf's running minimum estimator sets the current minimum to the future minimum periodically when their difference exceeds a threshold. Additionally, Apple argued that when a stationary estimator is unavailable, Helf's system sets the current estimate to the minimum after a defined period. Apple posited that a person of ordinary skill in the art (POSA) would modify Helf’s system to update the minimum values at regular intervals. In contrast, Andrea argued for a narrower definition of "periodically" as only "at regular intervals," supported by the patent's description that specifies the calculation occurs every 5 seconds. Based on this definition, Andrea contended Helf does not satisfy the "periodically" limitation, as it does not set the current estimate at regular intervals.

The Board's Final Written Decisions regarding the ’626 and ’627 Inter Partes Reviews (IPRs) concluded that Apple successfully demonstrated the unpatentability of claims 1–5, 10–25, and 38–47 of the ’345 patent, but not claims 6–9. For the ’626 IPR, the Board determined that a person of ordinary skill in the art (POSA) would not find it obvious to modify Hirsch’s system based on Martin's scenario without sub-windows (W = 1). The Board rejected Apple’s arguments involving multiple sub-windows (W = 2) in its reply brief, viewing them as a new theory of unpatentability raised for the first time. In the ’627 IPR, the Board accepted Andrea's proposed claim construction for "periodically," defining it as "at regular intervals of time," and found that Apple did not prove that Helf, alone or with Martin, satisfied the "periodically" limitation in claims 6–9.

The Board's ruling on Apple’s reply brief in the ’626 IPR is subject to abuse of discretion review. Apple claims the Board erred by not considering its reply arguments. IPR petitioners must clearly identify supporting evidence in their initial petitions, and replies can only address arguments made in the opposition or responses. The determination of whether Apple’s arguments regarding the Martin algorithm with multiple sub-windows were appropriate hinges on whether they were responsive to original arguments in its petition or the patent owner's response. Andrea argues that Apple intentionally based its petition on the W = 1 scenario, making the W = 2 discussion a new theory. However, the response asserts that Apple’s legal stance remained unchanged in its reply, continuing to argue that claims 6–9 are obvious over Hirsch and Martin, using the same prior art reference. Apple’s use of Martin does not constitute a new theory of unpatentability as seen in previous cases where new arguments were based on previously unidentified prior art.

The Board determined that Apple's reply declaration did not introduce a new argument, contrasting it with previous cases where new evidence or arguments extended beyond the scope of the original petition. Apple's reply clarified the Martin reference without citing new evidence and merely elaborated on previously discussed algorithms regarding the “current minimum” and “future minimum” limitations in claims 6–9. The Board's overly stringent evaluation of Apple's arguments was deemed unreasonable, as it implied that petitioners must cover all algorithmic variations or lose the chance to elaborate in replies. Furthermore, it is established that a petitioner can introduce new evidence in response to the patent owner’s arguments. Andrea’s opposition criticized Apple’s position based on the requirement of two sub-windows in Martin's algorithm, leading to a detailed rebuttal from Apple. The conclusion that Apple’s reply constituted new matter was viewed as an abuse of discretion. The court will review claim construction without deference, applying the Phillips standard rather than the broadest reasonable interpretation for expired patents.

Apple contends that the Board misinterpreted the term “periodically” in the ’627 IPR by not including the meaning “from time to time.” However, the written description of the patent supports the Board’s interpretation, indicating that “periodically” refers to actions occurring at regular intervals, specifically citing an example of calculations every 5 seconds. While preferred embodiments do not limit claims, if a claimed invention only encompasses a preferred embodiment, broader interpretations of claim terms may be questionable. Apple argues that the patent’s description of updating minimum values according to a “smoothed estimate” supports a broader construction of “periodically.” This argument is deemed unconvincing, as the claims in question (6–9) do not incorporate the “smoothed estimate” method and thus do not need to cover all embodiments described in the patent. The plain language of the claims does not align with the “smoothed estimate” method, and other claims that address this method do not include the term “periodically.” Therefore, the interpretation of “periodically” should remain consistent with its plain text and not be expanded based on extrinsic evidence.

The Board's decision relied on Dr. Douglas's expert testimony, which stated that the Board's interpretation of the term "periodically" in the ’345 patent was the only definition consistent with the patent's specification in the field of audio signal processing. Dr. Douglas defined "period" as the time it takes for an audio signal to repeat at regular intervals. In contrast, Apple’s expert acknowledged that outside the context of the ’345 patent, "periodically" means "at regular time intervals," but offered a vague interpretation when asked about its meaning within the patent, merely stating it indicated actions occurring at intervals, like every five seconds.

The Board considered this expert testimony to provide crucial context for understanding the technical aspects of the patent, consistent with legal precedents. Both experts supported the Board's definition of "periodically" as "at regular intervals of time." The Board's findings were deemed to be supported by substantial evidence, reinforcing that "periodically" should not be interpreted as "from time to time."

Regarding Apple’s claims that the Board erred in finding claims 6–9 of the ’345 patent were not anticipated or obvious, the Board rejected Apple's argument. Apple contended that the Helf reference met the "periodically" limitation through its running minimum estimator, which sets noise estimates at regular time intervals. However, substantial evidence indicated that Helf's running minimum estimator did not satisfy the "periodically" requirement. Helf utilized two methods for estimating background noise, where the running minimum estimator was a backup method employed only when the more accurate stationary estimator could not be used, indicating that its operation did not consistently adhere to the "periodically" limitation as defined by the Board.

Helf fails to meet the "periodically" limitation because it does not update the noise estimates Mk or Nk at regular time intervals, as Apple claims is necessary for the "current minimum." The running minimum estimator only updates the background noise estimate under specific conditions, and Apple argues that Nk is set to Mk 10 seconds after the system starts. However, this update is not considered periodic since it occurs only once when the running minimum estimator activates. Apple's suggestion that "power-cycling" the system could satisfy the limitation is rejected, as it would require manual intervention at regular intervals, undermining the purpose of the periodic update requirement. The Board's conclusion that Helf, in combination with Martin, does not disclose the "periodically" limitation is upheld, as substantial evidence supports this finding. The Board's determination that a skilled person would not have been motivated to modify the running minimum estimator to update at regular intervals is affirmed for claims 6–9 of the ’345 patent. The findings in the ’626 IPR are vacated and remanded for further consideration, while the findings in the ’627 IPR are affirmed. Additionally, Apple's misunderstanding regarding the Board's reasoning concerning claims 6 and 9 is noted; the Board's conclusion applies equally to both estimates involved.