Invalidity dossier
US 4811404
Noise suppression system
Current assignee: Motorola Solutions Inc
Added 9/17/2026, 2:33:07 PM
Active provider: DeepSeek · deepseek-flash
Patent summary
Title, assignee, inventors, filing/issue dates, abstract, and a plain-language overview of the claims.
Patent Overview — US 4,811,404 A
Title: Noise suppression system
Patent number: US4811404A
Application number: US07/103,857
Inventors: Richard J. Vilmur, Joseph J. Barlo, Ira A. Gerson, Brett L. Lindsley
Original assignee: Motorola Inc. (current assignee listed as Motorola Solutions Inc)
Priority/filing date: 1987-10-01
Publication (grant) date: 1989-03-07
Legal status: Expired – Lifetime (status listed as an assumption, not a legal conclusion)
Source: https://patents.google.com/patent/US4811404/en
Purpose
The patent relates generally to acoustic noise suppression systems, and more specifically to improving speech quality in a noise suppression system employing the spectral subtraction technique. Spectral subtraction divides the input signal into spectral bands via bandpass filters, estimates background noise power spectral density to derive a signal-to-noise ratio (SNR) per channel, computes a channel gain factor (used as a look-up table pointer for attenuation), attenuates the channels, and recombines them into a noise-suppressed output. In high-noise environments requiring suppression approaching 20 dB, the prior techniques produced voice degradation and a low-frequency "jet engine roar" flutter attributed to continuous channel-gain updating. Narrowband noise in a few high-energy channels produced a "running water" characteristic and degraded background-noise update decisions.
Plain-language scope
The system (800) includes: means (210) for separating the input signal into multiple pre-processed channel signals; means (310) for generating an SNR estimate per channel; means (590) for selecting a gain value from a gain table in response to the SNR estimates; and means (250) for modifying channel gains to produce post-processed noise-suppressed outputs. The described improvements add an SNR threshold mechanism (830) to eliminate minor gain fluctuations at low SNR, a voice metric calculator (810) for a more accurate background noise estimate update decision, and a channel SNR modifier (820) to suppress narrowband noise bursts.
What the excerpt does not establish
The excerpted text does not establish the full claim set, the complete specification, the exact contents of the incorporated prior-art patents (e.g., U.S. Pat. Nos. 4,630,304 and 4,630,305), or the details of the referenced McAulay and Malpass work. It also does not establish litigation, ownership transfers, validity, or the scope of any omitted text.
Generated 10/1/2026, 10:03:04 PM
Cases on file (0)
Specific litigation cases in our database that name US patent 4811404. The free-form analysis below may also discuss cases beyond this list.
No cases on file mention this patent. Upload a CSV or add a case manually in Admin → Manage litigation cases.
Litigation summary
Past and pending lawsuits — plaintiffs, defendants, jurisdictions, outcomes, and notable rulings.
Proceedings on file (0)
All PTAB activity →AIA trial proceedings (IPR / PGR / CBM) filed at the USPTO Patent Trial and Appeal Board against this patent. Sourced from the USPTO Open Data Portal and refreshed every six hours; each proceeding number deep-links to the PTAB E2E docket.
No PTAB proceedings on file. This patent has not been challenged via IPR, PGR, or CBM. The absence is itself a signal — well-asserted patents eventually attract IPRs. The LLM analysis below may surface filings the ODP feed hasn’t indexed yet.
PTAB challenges
AIA trial proceedings at the USPTO Patent Trial and Appeal Board — IPR, PGR, and CBM. Petitioners, judge panels, claim-level invalidation outcomes from Final Written Decisions, and Federal Circuit appeals. The single most important defensive datapoint after litigation history.
Assignment history
Inventors, original assignee, and the chain of ownership recorded with the USPTO — including the correspondent attorney who recorded each assignment, since shell-LLC chains often share one repeat-player attorney even when the entity names look unrelated. Surfaces NPE / patent-troll patterns: shell-entity transfers, known asserters in the chain, repeat correspondent fingerprints, pre-litigation assignments, and bankruptcy fire-sales.
Prior art
Earlier patents, publications, and products that may anticipate or render the claims unpatentable.
Obviousness
Combinations of prior art that suggest the claimed invention would have been obvious under 35 U.S.C. § 103.
Extensions
Patent term adjustments, term extensions, continuations, divisionals, family members, and expiration dates.
Derivative works
Defensive disclosure: derivative variations of each claim designed to render future incremental improvements obvious or non-novel.