# 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.

> Canonical page: https://elysiatools.com/en/hubs/audio-processing-regression-null-and-distortion-review

- **Keywords:** audio processing regression test, audio null test review, single tone THD comparison, DSP regression evidence, audio residual report

## Frequently asked questions

### Does the null test align or level-match automatically?

No. It subtracts decoded samples using only the supplied integer offset; it does not fit gain, correct polarity, remove DC or normalize.

### Does exactZero mean the entire files are identical?

No. It applies to compared decoded samples. Check excludedFrames and wholeFilesCompared, and use hashes separately for byte identity.

### Can I measure THD on a sweep or music?

Not with this analyzer. It expects a dominant stationary single tone and reports only selected in-band harmonics; it is not a THD+N or sweep measurement.

### Does a lower THD or quieter residual always mean improvement?

No. Deliberate distortion, gain and filtering may be requirements. Judge the documented case and preserve uncertainty rather than ranking sound quality from one number.

## Related content

- [Audio Test Signal Generation, Review and Handoff](https://elysiatools.com/en/hubs/audio-test-signal-generation-review-and-handoff): Create sweep, stereo or measurement-excitation fixtures, check their format and expected signal behavior, and hand off parameters, review evidence and file hashes without claiming a measured acoustic response.
- [Audio Master Lossy Codec Preflight and Delivery Checks](https://elysiatools.com/en/hubs/audio-master-lossy-codec-preflight-and-delivery): Preview a finished master through lossy encoding, inspect decoded peak and loudness changes, adjust only when necessary, and verify the exact final MP3, AAC or Opus delivery file.
- [Audio Measurement and Inspection](https://elysiatools.com/en/hubs/audio-analyze): Measure loudness, peaks, dynamics, musical descriptors, spectrum, and metadata before mastering, publishing, or archiving audio.