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Lossless Audio Authenticity Checker

· Last updated：2026-11-06

Locally screen FLAC and WAV for persistent spectral cutoffs. Inspect evidence, not a promise of authenticity.

Details

What this tool helps you do

Local spectral screening

Open a FLAC or PCM/float WAV in the interactive panel. Audio is decoded in a browser worker without resampling or uploading. Download a spectrum PNG and a JSON evidence report.

Honest conclusions

“Suspicious” means a persistent sharp spectral edge, not proven fraud. Genuine low-pass/old masters can trigger it. “No obvious traces” does not prove a lossless source: high-bitrate encodes, gradual rolloffs and unsampled edits can be missed. Silence, tones, short clips and low sample rates may be inconclusive. This is not a codec, bitrate, MDCT fingerprint, FLAC MD5 or effective-bit-depth detector.

Limits and API

100 MiB, 60 minutes, 8–192 kHz, mono/stereo. Native FLAC with known length, metadata ≤2 MiB and blocks ≤16,384 samples; PCM/float RIFF WAV (no RF64). Up to 384 evenly distributed 8192-sample Hann windows; displayed coverage is the analyzed fraction, not a confidence score. The server API only runs synthetic examples and rejects file inputs. For original-versus-encoded comparison, see Codec Artifact Detector.

Execution

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Written by the Elysia Tools team

Tool usage guide

Learn when to use this tool, what it supports, and how real users apply it.

Key facts

Category
Media
Input types
select
Output type
json
Sample coverage
4
API ready
Yes

Overview

Screen FLAC and PCM/float RIFF WAV files locally to detect persistent high-frequency spectral cutoffs that often indicate lossy transcoding. The tool renders a sampled spectrogram and average power spectrum, providing an exportable PNG image and a structured JSON evidence report without claiming absolute authenticity.

When to use

  • Screening downloaded or archived FLAC and WAV tracks for telltale 16 kHz to 20 kHz brickwall cutoff filters.
  • Checking whether high-frequency energy extends smoothly to the Nyquist limit or terminates abruptly.
  • Testing detection heuristics against synthetic broadband and low-passed reference audio.

How it works

  1. 1Select a reference signal under 'Try synthetic signals' ('Broadband noise' or 'Legitimate low-pass audio'), or select a local FLAC or WAV file within 100 MiB and 60 minutes.
  2. 2The local worker decodes the audio and evaluates up to 384 distributed 8192-sample Hann windows between 8 kHz and 192 kHz.
  3. 3Inspect the interactive spectrogram, power spectrum, and the percentage of analyzed coverage.
  4. 4Review the JSON verdict ('suspicious' or 'no-obvious-traces') and save the spectrum PNG or report data for your records.

Use cases

  • Library intake triage: Screen imported FLAC releases to flag potential lossy upconverts before cataloging them into high-resolution collections.
  • Mastering chain inspection: Examine WAV exports to verify whether aggressive brickwall anti-aliasing or master bus filters introduced sharp cutoff shelves.
  • Heuristic verification: Run the built-in synthetic noise profiles to observe how the detector handles wideband energy versus abrupt low-pass filter slopes.

Compare alternatives

  • Inspects container bit precision and integer low-bit occupancy rather than screening frequency cutoffs for lossy compression artifacts.

  • Measures single-tone harmonic distortion per channel instead of analyzing spectral bandwidth limits across complete musical tracks.

Who it's for

Best for

  • Screening FLAC and RIFF WAV music files for persistent high-frequency brickwall cutoffs.
  • Inspecting sampled spectrograms and average power spectra locally without sending audio to a server.
  • Demonstrating spectral cutoff detection behavior using synthetic test signals.

Not ideal for

  • Definitively certifying that an audio file has authentic analog or lossless source provenance.
  • Analyzing RF64 WAV files, non-PCM formats, or files exceeding 100 MiB or 60 minutes in length.

Edge cases & common failures

  • Legitimate low-pass filtering on historical recordings

    Vintage analog recordings or instruments naturally filtered below 20 kHz can trigger a 'suspicious' verdict; check whether the steep cutoff matches the recording's era and genre.

  • High-bitrate lossy transcode with subtle rolloff

    Encoders using high bitrates or gentle frequency slopes can result in 'no-obvious-traces'; an unflagged result does not prove original lossless quality.

  • Oversized FLAC metadata or unsupported blocks

    FLAC files with metadata blocks exceeding 2 MiB, block sizes greater than 16,384 samples, or unknown track lengths are rejected by the decoder.

Examples

1. Synthetic broadband noise evaluation

Audio archivist

Background

An archivist needs a baseline check to see how the analyzer handles continuous full-spectrum audio.

Problem

They need to confirm that an unfiltered broadband signal does not trigger false cutoff alerts.

How to use

Select 'Broadband noise' from the 'Try synthetic signals' dropdown and run the analysis.

demo: broadband

Outcome

The report outputs 'no-obvious-traces' with provenanceProven as false, reflecting full spectral continuity across active windows.

2. Synthetic low-pass signal verification

Audio quality technician

Background

A technician is testing the tool's ability to identify persistent brickwall filtering.

Problem

They want to verify how the tool flags audio with sharp high-frequency attenuation.

How to use

Choose 'Legitimate low-pass audio' from the 'Try synthetic signals' menu and review the spectral output.

FAQ

Does a 'suspicious' verdict mean the audio is definitely a lossy upscale?

No. A 'suspicious' result indicates a persistent, sharp high-frequency cutoff across sampled windows, which can also be caused by intentional low-pass filters or vintage recording equipment.

Does 'no-obvious-traces' confirm the recording is genuine lossless?

No. High-bitrate lossy encodes, gentle rolloff curves, short tracks, or unsampled sections can escape detection, and the tool never certifies lossless provenance.

What audio formats and specifications are supported?

Native FLAC (with known length, metadata up to 2 MiB, and block sizes up to 16,384 samples) and PCM/float RIFF WAV files up to 100 MiB, 60 minutes, mono or stereo, from 8 kHz to 192 kHz. RF64 is not supported.

Can I upload files to the server via the API?

No. The server API only runs synthetic demo signals and rejects file uploads; audio file screening is executed entirely in your local browser worker.

Does this tool verify FLAC MD5 hashes or detect effective bit depth?

No. It screens only for spectral bandwidth cutoffs and does not verify FLAC MD5 checksums, container bit depth, or codec-specific MDCT fingerprints.

Hub

FLAC/WAV Source Screening and Evidence Handoff

Screen suspected lossless audio, inspect spectral and integer-bit evidence, use reference comparisons only when justified, and deliver a traceable review without claiming authenticity.

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