# Audio Null Test Compare two audio files by direct sample subtraction and export residual measurements. > Canonical page: https://elysiatools.com/en/tools/audio-null-test - **Category:** Media - **Keywords:** Audio Null Test ## Overview 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. ## Inputs - **Reference audio (A)** (file) - **Comparison audio (B)** (file) - **B offset (samples)** (number) ## 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 - Upload a reference audio file (A) and a comparison audio file (B) of up to 30 seconds with identical sample rates and channel counts. - Set the sample offset parameter to shift file B forward or backward to compensate for known alignment differences. - The tool performs direct sample subtraction across the overlapping segment without applying normalization, resampling, or automatic gain matching. - Download 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. ## Frequently asked questions ### 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. ## Related tools - [Audio Noise Floor Timeline](https://elysiatools.com/en/tools/audio-noise-floor-timeline): Track a heuristic low-level RMS proxy over time, with separate digital-silence counts and per-channel change flags. - [Batch Audio Converter](https://elysiatools.com/en/tools/audio-batch-converter): Convert multiple audio files between different formats like MP3, WAV, FLAC, AAC, OGG, Opus with quality settings and batch processing - [Audio Format Converter](https://elysiatools.com/en/tools/audio-converter): Convert audio files between different formats like MP3, WAV, FLAC, AAC, OGG with quality settings and volume adjustment - [Audio Melody Contour Extractor](https://elysiatools.com/en/tools/audio-melody-contour-extractor): Extract a dominant melody path from audio and export MIDI, note events, a pitch contour, SVG, and JSON in one ZIP. - [Image Particle Music Visualizer](https://elysiatools.com/en/tools/image-particle-music-visualizer): Turn a picture into an audio-reactive point cloud. Preview locally, then export a 30 fps MP4 with music, a PNG poster and settings JSON. - [Audio Chord Progression Detector](https://elysiatools.com/en/tools/audio-chord-progression-detector): Estimate an audio file's chord sequence locally and download CSV, JSON, SVG, and method notes in one ZIP. - [Audio SNR Estimator](https://elysiatools.com/en/tools/audio-snr-estimator): Estimate per-channel signal-to-noise ratio from separate program and noise-only regions, with an offline ZIP report. - [Audio to Multitrack MIDI (Draft)](https://elysiatools.com/en/tools/audio-to-multitrack-midi): Split a full mix into stems (drums/bass/other/vocals) and transcribe each to MIDI — a multi-track starting point for transcription ## Samples - [Copyright-Free FLAC Audio Samples](https://elysiatools.com/en/samples/flac-samples): Lossless FLAC audio samples for testing and development, mirrored from MP3 set with nature sounds and meditation music - [Copyright-Free MP3 Audio Samples](https://elysiatools.com/en/samples/mp3-samples): Collection of royalty-free audio samples for testing and development purposes including nature sounds, meditation music, and ambient audio - [Copyright-Free WAV Audio Samples](https://elysiatools.com/en/samples/wav-samples): Uncompressed PCM WAV audio samples for testing and development, mirrored from MP3 set with nature sounds and meditation music - [Copyright-Free M4A Audio Samples](https://elysiatools.com/en/samples/m4a-samples): Apple iTunes compatible M4A audio samples with AAC encoding, optimized for quality and file size balance ## Related content - [Audio Processing Regression Tests: Null, Distortion and Report Handoff](https://elysiatools.com/en/hubs/audio-processing-regression-null-and-distortion-review): 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.