Audio Null Test | Online Free Tool | Elysia Tools

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

1Upload a reference audio file (A) and a comparison audio file (B) of up to 30 seconds with identical sample rates and channel counts.
2Set the sample offset parameter to shift file B forward or backward to compensate for known alignment differences.
3The tool performs direct sample subtraction across the overlapping segment without applying normalization, resampling, or automatic gain matching.
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.

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

Audio Null Test

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

Key facts

Overview

When to use

How it works

Use cases

Examples

1. Verifying Bit-Exact Master Copies

2. Compensating for Plugin Latency

FAQ

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