Open Audio Analyzer
LUFS, true peak and spectrum
Free · Designed for iPad. Not verified for macOS.
iPad
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
Ratings & Reviews
- This app hasn’t received enough ratings or reviews to display an overview.
Measurement:
- Correlation and Balance are now gated at −70 LUFS and read as a dash under it, where they read 0 before.
- A true-peak ceiling is no longer passed by silence.
- An Alert Meter on Crest now holds the most squashed block of a session rather than the most open one.
- An Alert Meter on ODR-I, LUFS-I, LRA, TP Max or Peak Max now prints what the engine holds, rather than the most extreme value that reading passed through.
- The two dynamics readings are Open Dynamic Range: ODR-S and ODR-I.
- ODR-S is undefined in silence and below the −70 LUFS absolute gate, rather than a number.
- The spectrum is measured on five signals.
- The Histogram records a column every 50 ms, where it recorded one every 100 ms.
- LUFS-M and LUFS-S are clamped at the −144 dB floor, which they were not.
- The Spectrogram records every published measurement.
Added:
- The Spectrum Analyzer has a cursor.
- The Oscilloscope's overlaid channels can be swapped front to back.
- The Histogram scrolls and zooms.
- A Validator chooses which criteria it judges.
- The Alert Meter chooses what it watches.
- The Alert Meter can print the distance from the target instead of the reading.
- A delivery target can set an ODR-I floor and an ODR-S floor.
- The Open Dynamic Range specification.
- The specification says what a reading means.
- Dynamic master is a seventh built-in delivery target.
- The text report prints ODR-I's band word after the reading.
- A file report states the lowest ODR-S reached.
- A connected DAW plugin is an entry in the source picker.
- The Spectrum Analyzer and the Spectrogram have a Source setting.
- The Spectrum Analyzer has a Range setting.
Changed:
- Clicking anywhere outside the selected module clears the selection.
- A level standing at the dB floor now reads -∞ rather than -144.0.
- The Super Meter's three centre sections stand apart.
- The Loudness Distribution prints its LRA in the caliper's grey rather than in the accent.
- The Super Meter's dynamics arcs end in nothing.
- The LUFS Meter's overshoot is the same solid as the bar under it.
- A new Alert Meter watches the live true peak rather than TP Max.
- The Oscilloscope's time base and overlaid legend moved onto the control row.
- Every number a module prints is the signal hue.
- The Validator colours a row by its own verdict.
- Every module's panel is lit from its top-left corner.
- The Histogram's time axis is elapsed time — 45s, 1m15s — where it was the wall-clock time a column was recorded at.
- The Histogram's momentary band is drawn at a weight you can see.
- The Histogram's overview strip sits a full gutter below the plot.
- The Alert Meter's reading is labelled with the metric's own name.
- The Alert Meter's panel is washed in light off its left edge, in the colour of the worst reading it has caught.
- The Alert Meter prints the unit after its reading.
Fixed:
- A meter with nothing to show no longer leaves a hairline of fill at the foot of its track.
- The LUFS Meter's bars no longer change height while the readings fall.
- The Phase Scope's correlation marker and a Number Box on Correlation no longer paint a reading of -0.00 as anti-phase.
- An Alert Meter in Delta no longer reads an em dash for ever on ODR-S or ODR-I.
- The source menu no longer offers "Open Audio Analyzer System Capture".
- Save overwrites the preset it opened, on the next launch as well as this one.
- The spectrogram's age axis stands still, and stands in the same place on the next launch.
- And the axis is the same picture every time the application starts.
- The Spectrum Analyzer's right-hand edge is one line rather than two.
- The Alert Meter drops what it has latched when it is asked to show something else.
- The spectrum analyser's peak hold no longer carries across a change of Source.
- The oscilloscope no longer loses a block of audio whenever two measurements land inside one display tick.
- The Stereo Cloud is readable on dense material.
Removed:
- PSR, PLR, DR-S and DR-I as names.
The developer, Jonas Grunau, indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy .
Data Not Collected
The developer does not collect any data from this app.
Accessibility
The developer has not yet indicated which accessibility features this app supports. Learn More
Information
- Seller
- Jonas Grunau
- Size
- 23.3 MB
- Category
- Productivity
- Compatibility
Requires iPadOS 15.0 or later.
- iPad
Requires iPadOS 15.0 or later. - Mac
Requires macOS 14.2 or later and a Mac with Apple M1 chip or later. - Apple Vision
Requires visionOS 1.0 or later.
- iPad
- Languages
- English
- Age Rating
4+
- 4+
- Copyright
- © 2026 Jonas Grunau
