The dataset's ranked leader holds 248 records out of 6,261 in scope, with the field dropping off quickly after that — fifth place holds 111 and tenth place holds 71. Even so, the top five combined only account for 13.5% of all records, so no single company controls the space outright. The remaining roughly four-fifths of filings are spread across a long tail of smaller and single-filing entrants, which matters for anyone assuming this is a two- or three-company market.

Filings peaked in 2019 at 255 and fell to 169 by 2024, a -26% move from the 229 filed in 2021. That looks like a real cooling trend over that window, but the two most recent years in the dataset (2025-2026) are still incomplete because patent publication typically lags filing by around 18 months. Treat any apparent drop in 2025-2026 as a data-completeness artifact rather than a confirmed slowdown until later publication catches up.

Transmission-related claims under H04B cover 21.6% of the 6,261 records, followed by acoustics and sound generation (G10K) at 18.6% and loudspeakers/transducers (H04R) at 17.6%. Speech and audio analysis, filter networks, and amplifiers each sit near 7.8%. Because a single record can carry multiple IPC classes, these figures overlap rather than sum to 100%, and they show where claim space is busiest, not where the best remaining opportunities are.

The narrower classes — filter networks (H03H) and amplifiers (H03F), both near 7.8% of records — carry noticeably less filing density than the core transmission and transducer classes above 17%. Specific claim territory such as individual ear-canal fit variation compensation, occlusion cancellation blended with hear-through audio, and cancellation-depth measurement methods also shows comparatively thinner coverage. These are reasonable starting points for a novelty search rather than guaranteed open ground, since density alone does not confirm the absence of blocking claims.

US12238473B2, filed by Starkey Laboratories and published in February 2025, is a representative recent example: it covers adaptive occlusion cancellation in an ear-wearable device that estimates the leakage path between an external sound source and the eardrum, then uses that estimate to update a hear-through filter. It illustrates how recent filings combine adaptive-filter methods with specific hardware constraints like occlusion and hear-through, rather than claiming broad noise-cancellation methods outright. Reviewing filings like this one is a useful way to see how claim scope has narrowed over time as the core adaptive-filter territory filled up.