Open Audio Analyzer

Open Audio Analyzer is a free and open-source loudness and spectrum analyzer: a canvas of meter modules you arrange yourself, driven by presets, delivery targets and skins.

FOURTEEN MODULES, AND EVERY ONE MEASURES SOMETHING

• LUFS Meter — momentary and short-term loudness as bars, integrated as a line • Super Meter — momentary, short-term and integrated as three concentric arcs • Digital Meter — sample peak and RMS, per channel, up to 7.1 • VU Meter — a needle on the movement the engine models, with its 0 VU reference printed on the face • Number Box — any single measurement, large • Alert Meter — one measurement watched, with the worst it has been latched • Validator — the delivery decision, as a table • Histogram — loudness against time: how the programme moved, and when it was over target • Loudness Distribution — how much of the programme sat at each loudness, bracketed between the percentiles the range spans • Spectrum Analyzer — level against frequency, log-spaced and tilted so a mix reads roughly flat, with peak hold • Spectrogram — frequency against time, level as colour • Oscilloscope — the waveform itself: triggered at scope speeds, rolling, or locked to a DAW's bar grid • Phase Scope — a goniometer, rotated so mono stands upright • Stereo Cloud — where each frequency sits in the stereo image, accumulated over time

MEASUREMENT YOU CAN CHECK

Momentary, short-term and integrated loudness, loudness range, true peak, sample peak, peak-to-loudness ratio and correlation — computed to ITU-R BS.1770-4 and EBU R 128. K-weighting coefficients are derived at the actual sample rate rather than read from a 48 kHz table, gating is R 128's 400 ms blocks at 75% overlap, and true peak is oversampled per BS.1770-4 Annex 2.

Loudness and true peak are held against the EBU Tech 3341 and 3342 conformance cases, and the spectrum against a sine of known amplitude, on every commit. The whole engine is public, so what a number means is something you can read rather than trust.

Anything this build cannot measure reads as an em dash, never as a zero: zero is a legitimate reading for correlation and for several decibel quantities, and a tool that fills a gap with a plausible number is worse than one that admits it.

DELIVERY TARGETS, AND A VERDICT

Six built in — −14 LUFS streaming, a loud streaming preset at −11, podcast at −16, EBU R 128, ATSC A/85 and CD — or write your own. The Validator turns integrated loudness, true peak and loudness range into one answer: ready to deliver, or not, and which line failed and by how much.

A SECOND SCREEN FOR THE STUDIO

Turn on PUBLISH in the desktop application — macOS, Windows or Linux — and this iPad draws that machine's meters over your own Wi-Fi: the same modules, the same painters, the same numbers, because both ends run the same code. It finds the machine by itself, reads a pairing code off its screen, or takes an address you type, because a venue's network blocks the first one.

On the desktop, a headless VST3 and Audio Unit plugin meters what your DAW is playing and streams it to the app, so what arrives on the iPad can be the mix as the DAW hears it, with the transport position beside it.

ON THE IPAD ITSELF

Meter the input iPadOS is routing, or open a file and read the report: integrated loudness, range, true peak, and the same delivery verdict.

MADE YOURS

Arrange modules on a grid and keep tabs of them. Save presets. Edit all thirteen colour roles of a skin in the app, each with its contrast ratio printed beside it. What you set up is remembered, as plain JSON you can read.

FREE, AND ACTUALLY FREE

No account, no subscription, no adverts, no analytics and no telemetry. The only network traffic is the meters you ask it to draw from another machine on your own network. Audio is measured and discarded — never recorded, stored or sent anywhere.

Licensed GPL-3.0-or-later; the measurement engine is MIT. Source, documentation and the desktop downloads: open-audio-analyzer.com