IP Law Daily, PATENT—Fed. Cir.: Federal Circuit upholds broad reading of ‘processor‘ in hearing device patent, (Oct 9, 2025)

By George Basharis, J.D.

The court agreed that the term “processor” did not require driving or exciting a signal, affirming a Patent Trial and Appeal Board decision that invalidated eleven claims as obvious.

The Federal Circuit has affirmed a Patent Trial and Appeal Board decision finding that claims of a hearing-related patent owned by ST Case1Tech LLC were unpatentable as obvious. The court held that the Board correctly interpreted the claim term “processor” as requiring the processor to evaluate seal quality but not to perform the additional task of driving or exciting a signal into the earpiece speaker (ST Case1Tech, LLC v. Squires, No. 23-2305 (Fed. Cir. Oct. 9, 2025)).

The decision leaves intact the Board’s determination that U.S. Patent No. 9,609,424, entitled “Method and Device for Personalized Hearing,” was anticipated by prior art and that its first eleven claims lacked patentable distinction over existing technology. The ruling also confirms the Board’s reliance on intrinsic and extrinsic evidence to define the scope of the processor limitation, reinforcing the principle that claim language must be interpreted according to its plain terms and contextual usage in the specification.

The disputed patent. Case1Tech’s ’424 patent discloses an electronic audio device designed to measure and evaluate the seal quality of an earpiece or headphone using built-in microphones and speakers. The patent describes circuitry, and a processor configured to analyze measurements made while driving or exciting a signal into the speaker, then to generate an audio or visual message indicating whether the earpiece is properly sealed.

Claims 1–11 of the ’424 patent define the core signal-analysis and feedback mechanism for assessing seal quality. Claims 12–20 introduce additional limitations or embodiments, including alternative operational modes such as adaptive equalization and multi-earpiece synchronization, and hardware distinctions such as wireless communication between earpieces and power-management features. Together, these claims describe a system that measures and reports the acoustic seal quality of an earpiece, with the processor analyzing data but not necessarily generating the test signal itself.

Samsung Electronics Co., Ltd. and Samsung Electronics America, Inc. petitioned for inter partes review, challenging the patent’s claims as obvious in view of prior art. In its final written decision, the Board found claims 1–11 unpatentable based on U.S. Patent Publication No. 2004/0196992 (Ryan), either alone or in combination with other references.

In the Ryan prior-art reference, the Board identified a component labeled “processing circuitry 40,” which performed the same functional role as the claimed processor in the ’424 patent. That circuitry received signals from the microphone and speaker, analyzed acoustic data, and adjusted or interpreted the output based on the detected seal or fit of the earpiece.

By equating the Ryan “processing circuitry 40” with the “processor” described in the ’424 patent, the Board concluded that Ryan already disclosed a system capable of evaluating seal quality using signal measurements. In other words, Ryan’s circuit performed the same analysis and feedback function that the ’424 patent claimed, leaving no patentable distinction.

Focus on the “processor” limitation. On appeal, Case1Tech argued that the Board misconstrued the processor limitation by omitting a requirement that the processor itself must drive or excite the signal into the speaker, rather than merely evaluate seal quality using measurements made during that process. The company contended that such a reading impermissibly broadened the claim and was inconsistent with the specification.

The Federal Circuit disagreed. The panel concluded that the plain language of claim 1 describes a processor “operatively coupled to evaluate a seal quality of the earpiece based on seal quality measurements made while driving or exciting a signal into the speaker,” but does not identify the processor as the component that drives or excites the signal. The clause “while driving or exciting a signal” merely defines when the measurements occur, not who performs that action.

The court emphasized that when a claim specifies certain processor functions explicitly, such as generating a visual or audio message, adjusting audio, or determining whether an earpiece is properly inserted, omitting the function of driving or exciting a signal elsewhere in the same claim indicates that the patentee did not intend to assign that duty to the processor. The absence of such wording, the court said, weighs against importing an additional limitation.

Support from the specification. The specification, according to the court, further supported a broad interpretation. It repeatedly describes operations that the processor “can perform” but never identifies signal driving or excitation as one of those required tasks. Moreover, it includes a disclaimer that the embodiments described are illustrative and not limiting, signaling to a skilled artisan that the claimed processor need not perform every action described in the embodiments.

Because the ’424 patent uses the transitional term “comprising,” its claims can encompass additional, unrecited components. That means another component within the device, not necessarily the processor, could carry out the driving or exciting function. The court noted that the Board correctly applied this principle in rejecting Case1Tech’s attempt to narrow the scope of the claim to exclude unrecited elements.

Arguments rejected on appeal. Case1Tech also sought to add a new argument that claim 1 required the processor to “make the seal quality measurements” in addition to evaluating them. The Federal Circuit declined to consider this issue because it had not been raised before the Board. The panel reiterated that parties cannot introduce new claim-construction arguments for the first time on appeal.

The court also declined to disturb the Board’s reliance on extrinsic evidence, including expert testimony from both sides. Because claim construction can rest on subsidiary factual determinations, the panel deferred to the Board’s decision to credit one expert over another. It found no reversible error in the Board’s conclusion that a person of ordinary skill in the art would interpret the processor limitation as encompassing evaluation only.

Having affirmed the Board’s claim construction, the Federal Circuit turned to the unpatentability finding. Case1Tech did not argue that, under the adopted construction, the prior-art reference Ryan failed to disclose the claimed processor. Therefore, the court treated the Board’s determination of obviousness as unchallenged on its evidentiary support. Accordingly, the panel affirmed the conclusion that Ryan disclosed a processing circuit performing the claimed evaluation function, rendering claims 1–11 of the ’424 patent obvious. The surviving claims, 12–20, were unaffected by the ruling.

The Case is No. 23-2305.

Judge: Taranto, R.

Attorneys: Timothy Devlin (Devlin Law Firm LLC) for ST Case1tech, LLC. Omar Farooq Amin, U.S. Patent and Trademark Office, for John A. Squires.

Companies: ST Case1tech, LLC

Cases: Patent FedCirNews USPTO