Every supply and return register is a two-way aperture — for air, and for sound from every room sharing the plenum.
In-Duct Silencers
Deep, inaccessible, professional-only.
Traditional duct attenuators require installation inside the ductwork — incompatible with retrofit, hidden in wall cavities, and sized for depth that residential construction rarely provides.
Plenum Box Grilles
50–200 mm of depth you don't have.
Specialty acoustic return grilles mount a separate absorptive box behind the face. The box does the acoustic work. The face is unchanged. Installation depth requirements eliminate most retrofit scenarios.
Duct Liners
Fiber shedding, degradation, IAQ risk.
Fiberglass and mineral wool bonded to duct interior surfaces degrade under airflow, shed particulates, and require full duct access — not a viable retrofit option in occupied buildings.
Active Noise Control
Power, maintenance, system complexity.
Active cancellation requires microphones, speakers, DSP, and electrical infrastructure at each register — eliminating residential applicability and adding maintenance burden in commercial settings.
"No prior art teaches integration of resonator geometry within the body of the register faceplate itself."
— VOXN-002-PROV Specification, Background Section
The Invention
Resonator geometry within the plate body.
The Voxnil cover plate replaces the standard non-attenuating register faceplate as a drop-in component — same dimensions, same mounting pattern, no duct modification — while co-forming Helmholtz resonator cells, tortuous-path channels, or hybrid geometry within the plate body thickness.
All resonator geometry is contained entirely within the body thickness T_b (10–25 mm). No portion protrudes beyond the room-facing or duct-facing surface. No blower, no insert, no plenum box. The faceplate itself is the attenuator.
Target: duct-propagated airborne sound in the 200–900 Hz speech-frequency range — the acoustic band responsible for cross-talk intelligibility between rooms sharing a common duct plenum.
Helmholtz Unit Cell Array
A periodic array of Helmholtz unit cells co-formed within the faceplate body. Each cell comprises a fully-enclosed cavity (32) with defined volume V_c communicating to the air-passage aperture through a neck passage (34) of width W and length L. Cavity and neck geometry are dimensioned to resonant frequency f_r = (c/2π)√(A_n/V_c·L_eff) within 200–900 Hz.
Multi-frequency variants incorporate two or more cell subsets at distinct resonant frequencies (|f_r1 − f_r2| ≥ 100 Hz) for broadened transmission-loss bandwidth. All geometry co-formed in a single injection molding or die casting operation.
Tortuous-Path Labyrinthine Channels
Meandering channels (40) defined entirely within the faceplate body thickness, with effective acoustic path length L_p ≥ 3×T_b (preferably ≥ 5×T_b). Path-length-dependent phase interference provides broadband attenuation across the 200–900 Hz range without discrete resonant peaks.
Channel hydraulic diameter D_h ≥ 3 mm and L_p/D_h ≤ 200 maintains acceptable pressure drop. Aggregate open passage area ≥ 75% of register-throat cross-section retained.
Membrane-Backed Cavity Resonators
A flexible membrane (60) co-formed as a reduced-thickness region of the faceplate body spans a portion of each air-passage aperture. A backing cavity (62) co-formed within the body behind the membrane creates a mass-spring-cavity resonant system tunable to 200–900 Hz by selection of membrane area, thickness, and cavity volume.
Membrane is a co-formed single-piece feature requiring no separate component, adhesive, or assembly step.
Hybrid Multi-Mechanism
Spatially distributed combination of Helmholtz cells (Zone 1, targeting 200–500 Hz resonant peaks) and tortuous-path channels (Zone 2, providing broadband path-length attenuation across 200–900 Hz) within a single unitary faceplate body.
Combined response provides improved attenuation depth at targeted low frequencies while maintaining broadband coverage — from a single drop-in replacement component. Within-body phononic crystal scattering arrays also claimed as an independent embodiment.
Fig. 3 — Helmholtz Unit Cell Detail
Patent Claims
45 claims across 3 independent families.
Docket
VOXN-002-PROV
CLAIM 1 · INDEPENDENT · DEVICE
Acoustic Register Cover Plate
A faceplate body with co-formed labyrinthine resonator array defined entirely within the body thickness — no protruding acoustic bodies, no blower, no supplemental plenum box structure required for attenuation of duct-propagated airborne sound in 200–900 Hz.
CLAIMS 2–12 · DEPENDENT · DEVICE
Resonator Embodiments
Helmholtz unit cells with geometric ratio constraints; multi-frequency broadband tuning (|f_r1 − f_r2| ≥ 100 Hz); tortuous-path channels with L_p ≥ 3×T_b; membrane-backed cavities; within-body phononic crystal arrays; hybrid multi-mechanism configurations.
Duct plenum terminating at register-throat with acoustic register cover plate as the sole acoustic attenuation component — no in-duct attenuator, no plenum box — passively attenuating duct-propagated sound from remote locations in 200–900 Hz.
CLAIMS 27–32 · DEPENDENT · SYSTEM
System Configurations
Drop-in retrofit compatibility; multi-frequency Helmholtz tuning; ≥10 dB transmission loss across 200 Hz bandwidth (ASTM E90); tortuous-path embodiment; shared return plenum cross-talk reduction; distributed multi-register deployment.
CLAIMS 33–45 · INDEPENDENT + DEPENDENT · METHOD
Method & Additional Device
Method of passively attenuating duct-propagated sound by replacing non-attenuating faceplate — ≤120 seconds, no tools, no duct modification. Plus: 250–800 Hz one-third-octave targeting; spatially distributed multi-mechanism zones; flush-profile installation; additive manufacturing embodiment.
Freedom to Operate
Prior art surveyed. Claim space is open.
FTO Analysis Complete — Inventor-Prepared · July 11, 2026
Nine references surveyed across USPTO, EPO, and CNIPA. The specific co-formation of resonator geometry within an HVAC terminal register faceplate body — without supplemental structures, powered components, or outwardly-protruding acoustic bodies — is not disclosed or suggested by any identified reference.
US 11,353,239 US 11,680,731Sound Reduction Grille Assembly — blower ventilator, outward-protruding phononic bodiesManaged
US 9,759,447Acoustic metamaterial for ducted HVAC — in-duct/in-throat structureClear
US 12,235,012 US 11,725,846Sound attenuation for HVAC furnace — combustion panel, separate attenuation panelsClear
US 6,116,375Acoustic resonator in HVAC conduit — in-duct onlyClear
EP 0,213,163Sound attenuation muffler box in flow channel — in-duct silencerClear
CN 109,346,051Perforated plate Helmholtz resonator — general acoustic panel, no HVAC registerClear
Commercial ArtSpecialty acoustic grilles (Price, Tuttle & Bailey) — separate plenum box, faceplate not attenuatingClear
Three mandatory claim distinctions from US 11,353,239
AGeometry Location. Resonator array is defined within the faceplate body thickness — not protruding outward from the room-facing surface. US 11,353,239 claims bodies extending outward annularly from the plate into room space.
BSound Source. Attenuation targets duct-propagated airborne sound from remote locations in shared plenum — not blower-generated rotational noise from a powered impeller integral to the assembly.
CNo Blower. Cover plate is a passive component with no integral blower, motor, impeller, or powered equipment at the terminal register location. US 11,353,239 requires a powered ventilation assembly blower.
DNo Plenum Box. No separate plenum box, baffle liner, or supplemental attenuation structure is required. Distinguishes specialty acoustic grille commercial art requiring 50–200 mm depth box structures.
This analysis is inventor-prepared and analytical only. It does not constitute a legal opinion. Formal FTO clearance should be obtained from registered patent counsel prior to commercialization.
Addressable Market
Every register in every building is an opportunity.
🏥
Healthcare
Patient privacy requirements under HIPAA create immediate demand for speech-isolation at every exam room register. No duct access required for retrofit in existing facilities.
🏢
Commercial Office
Open-plan and multi-tenant buildings share return air plenums across entire floors. Acoustic cross-talk between offices is a persistent complaint solved at the register face.
🏨
Hospitality
Hotel corridors and adjacent rooms share duct infrastructure. Drop-in register replacement during renovation achieves acoustic separation without structural work.
🏠
Residential
Master bedrooms, home offices, and media rooms sharing HVAC with family spaces. Consumer-installable in under 2 minutes — a new product category at retail.
This provisional — acoustic register cover plate with co-formed resonator geometry. 45 claims, 3 independent families, integrated FTO analysis.
≤ May 22, 2027
Non-Provisional Filing
Combined non-provisional claiming priority to both provisionals under 35 U.S.C. §119(e). Insert and cover plate embodiments in unified prosecution.
2028–2029
Examination & Grant
USPTO examination. Small entity status. Prosecution strategy hardened by prosecution disclaimer language in this provisional specification.
Docket Number
VOXN-002-PROV
Rev. 2 — July 11, 2026
Entity Status
Small Entity
USPTO filing fees at small entity rates
Inventor / Owner
Jeffrey D. Retherford
HeOntotita Corporation · Woodbridge, VA
Total Claims
45
3 independent · 42 dependent
Related Application
64/072,212
VOXN-001-PROV · Filed May 22, 2026
Non-Provisional Deadline
May 22, 2027
Governed by VOXN-001-PROV priority date
Licensing
Built for OEM integration.
Voxnil™ is structured for licensing — not manufacturing. The invention integrates into existing register product lines through tooling modification, not new supply chains.
The co-formed resonator geometry is producible in the same injection mold or die-cast tooling used for standard register faceplates, with cavity and core modifications to form the internal resonator geometry. No new materials. No new assembly operations. No new supply chain components.
Licensing targets include established HVAC terminal device manufacturers with existing register product lines, distribution networks, and OEM relationships with HVAC contractors and builders — the channels already serving the addressable market.
Exclusive Territory License
Exclusive rights within defined geographic territory or product segment — residential, commercial, or healthcare vertical — with performance milestones and royalty structure tied to units sold.
Non-Exclusive OEM License
Integration of Voxnil resonator geometry into existing register SKUs under licensee's brand. Per-unit royalty. Multiple licensees permitted across non-competing market segments.
Patent Assignment
Full assignment of patent rights upon non-provisional grant, with negotiated upfront and milestone payments. Inventor available for transition consulting and continuation strategy.
Co-Development Agreement
Joint development of specific embodiments, sizes, and performance targets with prospective licensee — including PoC validation testing and UL/AMCA certification pathway support.
Proof of Concept
Live acoustic simulation.
Physics-based Helmholtz resonator model and tortuous-path attenuation estimator. Adjust parameters and observe real-time response — the same geometry constraints recited in Claims 2–9.
Computational Proof of Concept · July 2026
From claim geometry to predicted transmission loss.
The simulators below implement the Helmholtz resonance equation f_r = (c/2π)√(A_n / V_c · L_eff) and a path-length phase interference model for tortuous channels — the same physical relationships that govern the co-formed resonator geometry in VOXN-002-PROV.
Parameters are bounded by the geometric ratio constraints recited in Claims 3 and 9: W/H_r ∈ [0.05, 0.25], D/T_b ∈ [0.10, 0.90], L_p/T_b ≥ 3. All computed resonant frequencies are evaluated against the 200–900 Hz target band of Claims 1, 26, and 33.
Speed of sound c = 343 m/s at 20°C, 1 atm. End-correction factor δ = 0.85√(A_n/π). Transmission loss curves use a Lorentzian resonance model with Q-factor derived from viscous losses in the neck passage.
Simulation modules
Module 1 — Helmholtz Unit Cell Calculator
Single-cell resonant frequency, Q-factor, and TL curve. Live cross-section geometry preview updates with sliders.
Module 2 — Tortuous-Path Channel Estimator
Path-length-dependent broadband attenuation across 200–900 Hz. Channel ratio and airflow retention output.
Module 3 — Multi-Cell Broadband Composer
Up to four Helmholtz cells at distinct frequencies. Combined TL curve shows broadband coverage vs. single-frequency baseline.
Module 1 — Helmholtz Unit Cell Calculator
12.0
16.0
16.0
3.0
3.0
8.0
18.0
20.0
--
In Band
RESONANT FREQUENCY fr (TARGET: 200–900 Hz)
--
Q-Factor
--
Peak TL (dB)
--
-3dB BW (Hz)
--
Cavity Vol (mm³)
--
D/Tb (Claim 3)
--
W/Hr (Claim 3)
→ Claims 2, 3, 4 · Helmholtz unit cell with geometric ratio constraints
MODEL: Path-length phase interference — TL(f) ≈ −20·log₁₀|cos(π·f·L_p/c)|
bounded below by viscous losses; above by channel aspect ratio
CONSTRAINT: L_p/T_b ≥ 3 (Claim 7) · Open area ≥ 60% (Claim 14)
Module 3 — Multi-Cell Broadband Composer · Up to 4 Helmholtz Cells
Enter cavity and neck dimensions for up to four Helmholtz unit cells. Toggle cells on/off. The combined TL curve (dashed gold) shows the broadband coverage achieved by multi-frequency tuning — the core of Claims 4 and 5 (|f_r1 − f_r2| ≥ 100 Hz broadened bandwidth).
This simulation implements linearized acoustic models (Helmholtz resonance equation, Lorentzian TL approximation, path-length phase interference). Results are theoretical estimates; actual transmission loss will vary with material damping, manufacturing tolerances, airflow turbulence, and installation conditions. Computational results support patent claim scope and are not a substitute for physical prototype testing under ASTM E90 or ISO 10140-2 measurement standards. Physical prototype testing is the next development milestone.
License Inquiry
Ready to integrate silence into your line?
Sound damping. Airflow uncompromised. Licensing inquiries, technical data requests, and co-development discussions welcome. NDA available on request.
