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Audio Null Test

· Last updated：2026-10-23

Compare two audio files by direct sample subtraction and export residual measurements.

Details

What this tool helps you do

Both inputs must be at most 30 seconds with identical sample rates and channel counts. Positive B offset discards leading B samples; negative discards A. Only overlap is tested. No automatic alignment, gain/polarity matching, resampling or normalization. ZIP contains per-channel metrics, CSV, waveform SVG and unnormalized float32 residual.wav; values may exceed full scale. Zero logarithms and silent-reference ratios are null. Exact zero describes compared samples only.

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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
file, number
Output type
file
Sample coverage
4
API ready
Yes

Overview

The Audio Null Test tool performs direct sample-by-sample subtraction between two audio files to measure differences and verify transparency. By subtracting a comparison file from a reference track over their overlapping region, it quantifies any variation and exports residual metrics, a CSV report, a waveform SVG, and an unnormalized float32 residual audio file packaged in a ZIP archive.

When to use

  • Verifying bit-exact export integrity between original source audio and DAW render files.
  • Testing whether a plugin, converter, or codec produces audible or measurable changes at unity gain.
  • Evaluating sample-level delay between two recordings to confirm exact cancellation.

How it works

  1. 1Upload a reference audio file (A) and a comparison audio file (B) of up to 30 seconds with identical sample rates and channel counts.
  2. 2Set the sample offset parameter to shift file B forward or backward to compensate for known alignment differences.
  3. 3The tool performs direct sample subtraction across the overlapping segment without applying normalization, resampling, or automatic gain matching.
  4. 4Download the generated ZIP archive containing per-channel metrics, a CSV log, an SVG waveform comparison, and a 32-bit float residual WAV file.

Use cases

  • Digital Audio Workstation (DAW) render verification to ensure bounce settings produce identical audio output.
  • Lossless codec verification to confirm that decoded FLAC or ALAC files perfectly cancel against source WAV files.
  • Hardware and plugin linearity checks to isolate harmonic distortion, dither noise, or filtering artifacts.

Examples

1. Verifying Bit-Exact Master Copies

Mastering Engineer

Background

An engineer needs to confirm that a bounced master file exactly matches the unprocessed reference mix print.

Problem

Manual listening cannot reliably detect minute single-bit shifts or unintended digital processing.

How to use

Upload the unprocessed reference as file A, the bounced track as file B, set B offset to 0 samples, and run the test.

referenceFile: master_ref.wav, comparisonFile: master_bounce.wav, offsetSamples: 0

Outcome

Receives an exact zero residual across all channels, confirming bit-identical output.

2. Compensating for Plugin Latency

Audio Software Developer

Background

A developer is verifying that a utility plugin produces zero signal degradation after accounting for fixed DSP buffer delay.

Problem

The processed file exhibits a fixed 120-sample delay that prevents direct cancellation without offset adjustment.

How to use

Upload the dry file as reference A and the processed file as comparison B, setting the B offset to 120 samples.

FAQ

What audio requirements must both files meet?

Both files must have identical sample rates and channel counts, and each must be 30 seconds or shorter.

Does the tool automatically match gain or align samples?

No. The tool does not perform automatic gain matching, polarity inversion, or alignment; use the manual offset option to shift samples.

How does the sample offset parameter work?

A positive offset discards leading samples from file B, while a negative offset discards leading samples from file A.

Why is the residual WAV exported in 32-bit float format?

Unnormalized float32 preserves exact subtraction differences without clipping or scaling, even if values exceed 0 dBFS.

What files are included in the downloaded ZIP archive?

The ZIP contains per-channel measurement values, a CSV data table, a waveform visualization in SVG format, and residual.wav.

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.

Hub

Audio Processing Regression Tests: Null, Distortion and Report Handoff

Compare a fixed audio reference with separately processed outputs, document null-test coverage and suitable single-tone THD results, and deliver a reviewed regression record with files and hashes.

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referenceFile: dry_signal.wav, comparisonFile: wet_signal.wav, offsetSamples: 120

Outcome

Leading samples on B are discarded, aligning the tracks to produce an exact null on overlapping samples.