FreqCheck™

1. WHITE PAPER: IND CORE™ ARCHITECTURAL METHODOLOGY & PROCESSING CONSTRAINTS

The FreqCheck™ telemetry engine replaces legacy dynamic signal analyzer (DSA) workstations by executing deterministic, real-time Fast Fourier Transform (FFT) spectral decomposition—dynamically scaling from 32,768 to 65,536 points based on the active hardware clock—directly on Apple devices (iOS, iPadOS, macOS, and visionOS). Hanning-windowed signal segmentation prevents spectral leakage across discrete bins, while calibrated RMS amplitude integration ensures absolute repeatability across continuous acoustic, vibrational, and ballistic captures.

Bench-Verified IEC 61672 Class 1 Acoustic Compliance: In technical collaboration with ROGA Instruments (Germany), FreqCheck was formally validated against certified laboratory Type 308 sound level meter standards via synchronized sine sweep injection. FreqCheck tracks certified reference hardware within 0.1 dB to 0.2 dB, operating strictly inside the ±0.5 dB Class 1 corridor across 20 Hz to 20,000 Hz. The engine executes standard mathematical weighting directly on unadulterated ADC voltage: certified A-weighting (dBA), C-weighting (dBC), and Linear (Lin-Z) curves paired with true exponential RMS integration constants: Fast (125 ms), Slow (1000 ms), and Impulse.

Quad-Mode Metrological Routing: The v4.1.5 architecture operates across four distinct operational pipelines:

• Standard Mode: Deploys factory-calibrated internal microphone profiles and adaptive background noise cancellation tuned for workplace OSHA surveys, municipal noise ordinances, and ambient infrasonic baselines without requiring external accessories.
• Pro Input Mode (PIM): Completely disables iOS Automatic Gain Control (AGC) and noise gates. Raw, unadulterated voltage from external class-compliant (UAC-2) digitizers feeds directly into the DSP engine at locked clock rates of 44.1 kHz, 48.0 kHz, 96.0 kHz, 192.0 kHz, or 384.0 kHz. PIM enforces discrete channel mapping (Ch 1 / Ch 2), calibrated sensitivity coefficients (mV/Pa, mV/g, mV/m·s²), configurable ADC reference ceilings (10.0V / 16.6V), and features an integrated Universal Pistonphone Calibration tool (94.0 dB / 114.0 dB at 250 Hz / 1000 Hz) for Class 1 physical transducer verification. A switchable Real-Time Hardware DC Block eliminates analog baseline drift before FFT ingestion while preserving 0.20 Hz infrasound.
• Wideband Metrology Mode (WB): Unlocks the high-frequency acoustic and ultrasonic bandwidth (30 Hz – 192 kHz) at a 384 kHz Nyquist sampling clock. WB Mode is engineered for dual-domain metrology: capturing transient impulse events with microsecond rise times while executing continuous ultrasonic spectral tracking for predictive machinery maintenance, pressurized gas leaks, and electrical corona ionization without slew-rate distortion.
• Dynamic Pulse Sequence (DPS): Automates peak-hold event counting, logs microsecond rise times, calculates A-duration thresholds, and generates tamper-evident audit logs conforming to MIL-STD-1474E, TOP 4-2-822, and ASTM F2439 ballistic test standards.

External Hardware Bridge & Multi-Modal Sensor Pairing: Pro Input Mode natively interfaces with standard laboratory instrumentation via USB-C or Lightning adapters. Bench-verified with ROGA Instruments hardware—including the RogaDAQ 384, Plug.n.DAQ Lite (2-channel UAC-2), iSV1611 USB microphone series, and MP30-HSPL high-SPL transducers—the architecture maintains line integrity and flat frequency response over BNC cable runs up to 50 meters under intense impulse overpressures exceeding 175 dB SPL.

For post-process media auditing, the engine ingests professional uncompressed and lossless formats—.wav, .flac, .alac, .aiff, .m4a, and .mp3—up to audiophile resolutions of 24-bit / 384 kHz.

Live Telemetry Buffer Retention: During continuous live monitoring, the system maintains a high-resolution rolling buffer capturing the most recent 5 to 15 minutes of spectral telemetry. This guarantees ISO 17025-aligned forensic reporting precision while preventing processor memory saturation by cyclically committing older samples as fresh data enters the pipeline.

To eliminate processor thermal throttling and phase skew, imported files are strictly governed by duration thresholds: maximum 2 minutes (120 seconds) for video and 3 minutes (180 seconds) for audio. The native AVAssetReader framework processes the complete recording end-to-end with dynamic sample rate decoding—preserving bit-for-bit mathematical characteristics at native capture resolution without forced interpolation.

ZERO-DRIFT EDGE PROCESSING DELIVERS MATHEMATICAL PURITY WITHOUT ARTIFICIAL INTERPOLATION.

2. STANDARD OPERATING PROCEDURE (SOP): PROFESSIONAL INGESTION & FIELD METROLOGY

To maintain full ISO/IEC 17025 compliance and generate defensible evidentiary records across municipal, industrial, and defense testing, operators must adhere to the following protocol:

1. 1. Live Hardware Configuration & Transducer Coupling — When acquiring live signals—including sub-Hz infrasound, industrial machinery vibration, ultrasonic gas leaks, or MIL-STD-1474E ballistic overpressures—connect your external UAC-2 DAQ interface or USB measurement transducer, open Instrumentation Settings from the Main Menu, and activate Pro Input Mode (PIM). This completely disengages iOS Automatic Gain Control (AGC), noise suppression, and heuristic filters, unlocking direct engineering controls:
   • Hardware Sample Clock Lock: Lock to native hardware clocks (44.1, 48.0, 96.0, 192.0, or 384.0 kHz) to eliminate OS-level resampling and maintain NIST-traceable phase linearity.
   • Real-Time Hardware DC Correction: Toggle ON to neutralize analog offset and thermal sensor drift prior to FFT decomposition.
   • ADC Reference Ceiling (V): Enter digitizer full-scale voltage ceiling (e.g., 10.0V for ROGA Plug.n.DAQ Lite / RogaDAQ 384, or 16.6V for high-voltage DAQ bridges).
   • Transducer Sensitivity: Enter certified factory sensitivity coefficients matching your calibration sheet (e.g., 1.02 mV/Pa for high-SPL acoustic capsules; 10.0 mV/g or 100.0 mV/g for IEPE accelerometers).
   • IEC 61672 Weighting Curve: Select dBA (human acoustic response), dBC (low-frequency / structural impact noise), or Lin-Z (unfiltered flat linear response from 0.20 Hz to 192 kHz).
   • RMS Time Integration: Select certified exponential time weighting matching physical laboratory meters: Fast (125 ms), Slow (1000 ms), or Impulse (35 ms rise / 1500 ms decay).
   • Hardware Channel Assignment: Route discrete inputs (Left Ch 1, Right Ch 2, or Auto) for multi-channel acquisition.
   • Physical Unit Scaling: Set active telemetry units to dB SPL, m/s² (or g), or full-scale voltage (dBFS).
   • Universal Pistonphone Field Calibration: Before active testing, couple a standard acoustic calibrator or pistonphone (94.0 dB or 114.0 dB at 250 Hz / 1000 Hz) over the measurement microphone. Activate 'Pistonphone Calibration' in Instrumentation Settings; the engine locks onto the mechanical reference tone, calculates the precision gain offset, and aligns the software to live ambient temperature and barometric pressure.
   • Wideband Metrology (WB) & DPS Mode: Engage WB for continuous ultrasonic surveillance up to 192 kHz, or activate the Dynamic Pulse Sequence (DPS) engine for threshold arming, peak overpressure capture, and A-duration ballistic logging.
   These values must be transcribed directly from verified calibration certificates. Once committed, parameters are permanently locked to an immutable metrology snapshot for that testing session.
   

   1a. Preset Slot Memory — Operators may commit the verified configuration parameters to either of two persistent hardware preset slots within Pro Input Mode. Recalling a saved slot restores all clock rates, ADC ceilings, sensitivity values, and filter weightings simultaneously, eliminating manual setup errors during rapid field transitions.

   (Note: Configuration parameters are bypassed during post-process media file imports, which instead use dynamic file decoding.)
2. 2. Media File Ingestion & Retroactive Recertification — For post-event forensic auditing, import uncompressed or lossless audio/video files (.wav, .flac, .aiff, .alac, .mp4, .mov). Ensure files adhere to stability duration thresholds: maximum 2:00 minutes for video and 3:00 minutes for audio. In PIM, input the original recording parameters (sample rate, sensor mV/Pa or mV/g, and voltage ceiling) to retroactively execute full 65,536-point FFT decomposition, IEC weighting curves, and ballistic peak extraction on past recordings.
3. 3. Interactive HUD Forensics & Signal Validation — In live or post-test review, engage the interactive crosshair ghost-trace scrubber to interrogate active telemetry or frozen peak-hold envelopes across the 30 Hz to 192 kHz spectrum. For continuous sweeps, inspect the Algorithmic Signal Integrity Score (1.0–5.0) to confirm spectral purity and signal-to-noise margins before audit commitment.
4. 4. Cryptographic Sealing & Enterprise LIMS Export — Execute report generation to seal the measurement session. FreqCheck permanently binds all raw FFT telemetry, timecode event logs, hardware channel assignments, IEC weighting selections, and the device's hardware signature using an unalterable SHA-256 cryptographic hash. The resulting tamper-evident PDF audit sheet meets ISO/IEC 17025 chain-of-custody protocols for seamless ingestion into enterprise Laboratory Information Management Systems (LIMS).

STANDARDIZED OPERATIONAL PROTOCOLS GUARANTEE UNASSAILABLE FORENSIC EVIDENTIARY WEIGHT.

3. ISO/IEC 17025:2017 CALIBRATION CERTIFICATE & BENCH VERIFICATION

FreqCheck™ integrates NIST-traceable calibration directly into edge Apple hardware, bypassing legacy dynamic signal analyzer (DSA) overhead and multi-day calibration turnaround times. The IND CORE™ DSP engine operates as an accredited metrological instrument (ISO/IEC 17025:2017 Cert #05122C9A 2602), evaluated via precision electrical injection with a certified measurement uncertainty of 0.20 dB.

In addition to character validation across the 4.0 Hz to 100.0 Hz infrasonic baseline, acoustic performance was bench-verified across the complete audible spectrum (20 Hz to 20,000 Hz) in technical collaboration with ROGA Instruments (Germany). Using a synchronized sine sweep feeding a certified Type 308 Class 1 Sound Level Meter and FreqCheck via the Plug.n.DAQ Lite interface simultaneously, FreqCheck tracked reference hardware within 0.1 dB to 0.2 dB—operating well inside the ±0.5 dB IEC 61672 Class 1 tolerance corridor across all standard frequency bands.

YOU COMMAND THE HIGHEST GLOBAL STANDARD OF ACOUSTIC METROLOGY DIRECTLY FROM YOUR DEVICE.

(Calibration Certificate: #05122C9A 2602 • Traceable to NIST Standards • Uncertainty: 0.20 dB)

4. IND CORE™ FULL SPECTRUM SWEEP: 1Hz TO 100Hz

The IND CORE™ engine tracks and processes continuous tonal sweeps from 1Hz to 100Hz, operating independently of the standard mobile audio roll-off constraints that would normally cut this range short.

The absolute physical truth of a signal — across the entire infrasonic and low-audible baseline — gets captured intact, not filtered out before you ever see it.

EVERY MEASUREMENT REFLECTS THE PRECISE PHYSICAL REALITY, END TO END.

5. IND CORE™ ENGINE TECHNICAL AUDIT CASE STUDY

The engine reconciles discrete spectral signatures across the deepest infrasonic and high-frequency bands, automatically eliminating background noise and spectral leakage. The Algorithmic Signal Integrity Scoring system calculates a real-time Signal Score (1.0–5.0) using proprietary temporal and spectral evaluation algorithms protected under our patent portfolio, continuously auditing the structural purity and stability of the target frequency against ambient noise.

You receive a mathematically validated integrity metric instead of a visual approximation you'd otherwise have to eyeball and trust.

YOUR ACOUSTIC ANALYSIS IS BACKED BY INDISPUTABLE, MATHEMATICAL PROOF.

6. SYSTEMATIC DIGITAL OFFSETS & IEC 61672 CLASS 1 TOLERANCE VERIFICATION

Every digital metrology instrument slices continuous analog signals into discrete frequency “bins” determined by sample rate ($f_s$) and transform length ($N$). Consumer acoustic apps frequently deploy visual interpolation or cosmetic rounding to force readings to match clean integers (e.g., displaying “80.0 Hz”). FreqCheck strictly forbids cosmetic post-processing: an instrument that alters its data for cosmetic convenience loses legal and forensic evidentiary standing.

An 80 Hz test tone is reported at the exact mathematical center of its active FFT bin—approximately 79.4079 Hz—demonstrating raw algorithmic transparency. The table below documents the systematic, deterministic frequency offsets produced by a standard 1.3458 Hz bin width in the 30 Hz to 100 Hz band at 44.1 kHz sampling:

TOTAL ALGORITHMIC TRANSPARENCY GUARANTEES THE ABSOLUTE FORENSIC INTEGRITY OF YOUR RESULTS.

Metrological Conclusion: These variances are systematic, reproducible, and non-random—confirming the engine executes pure discrete Fourier transforms without synthetic smoothing. Furthermore, tracking reference meters within 0.1 to 0.2 dB verifies amplitude linearity well inside the ±0.5 dB corridor required for Class 1 acoustic compliance.

For downloadable test files to verify this behavior yourself using your own source material, see Data Importing.

7. METROLOGICAL TRACEABILITY & HARDWARE VALIDATION

The FreqCheck™ DSP engine operates as a character-verified instrument, tested via direct electrical injection against ISO/IEC 17025 standards from 4 Hz to 100 Hz — confirming the software's mathematical accuracy independent of any specific microphone or recording condition.

The certification describes the engine itself, proving mathematical integrity across every measurement.

THE MATH IS CERTIFIED. WHATEVER YOU POINT IT AT INHERITS THAT CERTIFICATION.

For details on external DAQ bridging, DC-coupled line-in routing, and qualified hardware, see Hardware & Pairing.