github.com/JonasGrunau/open_audio_analyzer
A free and open-source loudness and spectrum analyzer. Fourteen meter modules on a canvas you arrange — on the desktop, inside your DAW, and on a tablet beside the desk.
Not a video or simulation. Those are the application's own meter modules, the same code the desktop runs, drawing in your browser from the engine's own readings of “Apathy And Resignation Are The Sources Of Our Misfortune” by Citizens Of The Empire, CC BY 3.0. It is one measured pass of that track, replayed on a fixed canvas of eight; the canvas you arrange is the application's.
How it works
Insert the plugin on your master bus and open the app on the desktop beside you: that is the setup. If you would rather read the meters from where you are standing than from where the computer is, a tablet across the room attaches to the same session and draws them too. You are not routing audio anywhere or matching one meter against another.
Nothing along this path measures anything twice. The plugin takes the readings, the desktop draws them, and the tablet across the room draws the same ones — one engine, one set of numbers, three places to read them. So the meter you glance at from the far side of the studio cannot quietly disagree with the one under your hand. The two photographs below are that claim rather than an illustration of it: they were taken from one frozen frame of one session, with the tablet attached to the desktop beside it, which is why every reading in them is the same reading.
01 In your DAW
Insert the VST3 or the Audio Unit on your master bus. It draws no meters of its own: the panel says the link is live and that is all it does. What it measures goes to the app, along with where your playhead is.
02 On the desktop
The canvas you arranged, every module on it reading the same instant of the same audio. It makes no difference whether that audio came from the plugin, from an input or from a file: the meters are the same meters.
03 Across the room
Press PUBLISH on the desktop and ATTACH on an iPad, and the tablet draws that canvas — the same application, the same modules, the same painters, over Wi-Fi. It is not measuring anything of its own: what is on it is the frame the desktop published. What you arranged on a 32-inch monitor opens on the tablet still looking arranged, not squashed.
Modules
You choose which of them are on screen. In the application, right click the canvas — long press it on a tablet — to add a meter, then drag it where you want it and size it: loudness and a delivery verdict when you are finishing a master, a spectrum and a phase scope while you mix, a VU and a waveform while you track. The arrangement you settle on saves as a preset, for the desktop and for the tablet beside it.
Any single measurement, as a number.
Momentary, short-term and integrated loudness as three bars against a target band, each with its value beneath.
Loudness from the left and Open Dynamic Range continuing from its tip to the true peak, on one half-gauge; LUFS, PLR and true peak in the centre.
Sample peak and RMS, per channel, up to 7.1 — as segmented bars and as numbers.
A needle, with the ballistics of the real thing.
One measurement, watched, with the worst it has been latched — the reading itself, or its distance from the target.
The delivery decision, as a table.
Loudness against time: how the programme moved, and when it was over target.
How much of the programme was spent at each loudness.
Level against frequency, log-spaced, with a peak hold.
Frequency against time, with level as colour.
The waveform itself, one lane per channel or both overlaid.
A goniometer: left against right, rotated so mono stands upright.
Where each frequency sits in the stereo image over the last two seconds, one mark per band per frame.
Measurement
| Reading | What it is |
|---|---|
| Loudness | LUFS, weighted the way ITU-R BS.1770-4 says: low end counts for less, presence for more, so the meter agrees with your ears about what is loud instead of counting energy. Worked out at your material’s own sample rate, not at 48 kHz and hoped. |
| Integrated | The whole programme as one number, gated to EBU R 128: passages far below the rest are left out, so the silence between phrases and the fade at the top do not drag it below what the track sounds like. |
| Momentary / Short-term | 400 milliseconds and 3 seconds. One is what a transient does to your loudness; the other is what a section does. |
| LRA | Loudness range: how far the loud parts of the programme sit above the quiet ones. It is the number a broadcaster asks for, and the one that says whether a master has been flattened. |
| True peak | The peak between samples as well as on them, oversampled four times as BS.1770-4 requires. It is the number a delivery ceiling means, and it sits above the sample peak your DAW shows — by as much as a dB and a half on heavily limited material. |
| Open Dynamic Range | True peak minus loudness over the same audio: PSR over the last three seconds, PLR over the whole programme — the names every meter prints, defined to the operand in the ODR specification, whose own ODR-S / ODR-I is one setting away. How hard the limiter is working, in a number that does not move when a platform turns the track down. |
| Spectrum | 512 bands, spaced the way you hear rather than the way the arithmetic falls out. Each band shows the loudest thing in it rather than the average, so a narrow resonance stands at its real height instead of being smoothed into the noise beside it. |
| Correlation | How alike the two channels are: +1 is mono, 0 is uncorrelated, −1 is one channel inverted against the other. |
| Crest | Peak minus RMS: how much room the transients have above the body of the sound. A sine is 3.01 dB, a snare is a lot more, and a master that has been squeezed trends towards nothing. |
| Clip | The longest run of samples pinned at full scale since you last reset, per channel. It stays on screen, so a clip three samples long is still there when you come back to look for it. |
Dynamics
There is no standard that says what “dynamic range” is, so Open Audio Analyzer publishes one. ODR-S is the true peak of the last three seconds against the short-term loudness of the same three seconds: how much room the loudest moment of a passage has over how loud that passage is. ODR-I is the same question about the whole programme — the highest true peak against the integrated loudness. Watch either one fall as you push a limiter and you are watching the squeeze happen.
These are the readings the AES calls PSR and PLR, and that is what Open Audio Analyzer prints — the names every other meter prints, and the ones a person looks for. What the AES text says is “true peak against loudness” and little else; what the specification adds is everything it leaves open: which channel’s peak, both operands over the same window, undefined in silence rather than reading zero, the most squeezed three seconds reported beside the whole. It is held in CI against arithmetic — a stereo sine reads exactly 0.0 LU on both — and a delivery target can put a floor under either, so a master limited past it fails the same way one over its peak ceiling does. Settings › Dynamics switches every label to the specification’s own, ODR-S and ODR-I; nothing but the name changes, on the canvas, in a report or on a paired tablet.
| Reading | Is | Undefined while |
|---|---|---|
| PSR · ODR-S | TP(3 s) − LUFS-S, the last three seconds | LUFS-S is at or below the −70 LUFS absolute gate |
| PLR · ODR-I | TP Max − LUFS-I, the programme since reset | LUFS-I is undefined |
| min PSR | The lowest PSR the programme reached, where it was defined | PSR has never been defined |
Reading the number
Normalise a master to a target and its true peak lands at the target plus its ODR-I — so under −14 LUFS and a −1 dBTP ceiling, 13 LU is the most a platform can play at its own level. The bands are the specification’s Annex A: the anchors are arithmetic on published delivery levels, the names are editorial, and 7 LU is a choice in a techno track and a casualty in a string quartet.
Plugin, tablet and CLI
A VST3 and an Audio Unit, on a track, a bus or the master, mono through 7.1. What you read while mixing is not a second set of meters built to look like the first — it is the first, watching your session. Tested in Ableton Live, Logic Pro, Cubase, FL Studio and Studio One.
It finds the desktop by itself, or reads a pairing code off its screen with the camera, or takes an address you type — three ways in, because the first one is what a venue’s Wi-Fi blocks. Publishing stays off until you switch it on, and there is no password on the link: switch it on at home, not on a network you do not control.
oaa measures a file without opening anything — one track, or every file in an
album folder in one go — and prints a report you can read or a CSV for a spreadsheet. It is
the same analysis the app runs on live audio, down to the last decimal, with
nothing resampled or remixed on the way in.
$ oaa master.wav # the whole report, readable
$ oaa --target streaming-14 master.wav # …and does it pass?
$ oaa --target streaming-14 album/*.wav # the whole album, one pass each
$ oaa --format csv -o loudness.csv master.wav # loudness over time, for a spreadsheet
$ oaa --list-targets # what you can measure againstConfiguration
Save an arrangement of meters as a preset and it opens that way next time: the same modules in the same places, on a 32-inch monitor or on the tablet beside it. Presets, delivery targets and colour schemes are small text files in a folder you can open, so your setup travels to the studio machine, or to somebody who works the way you do.
A delivery target is the numbers you have to hit: a loudness, how far either side of it you may land, a true-peak ceiling, and a limit on how much the loudness may move across the track. The streaming and broadcast ones come with the app. If your label, your client or your own ears say otherwise, write your own — give it the name of one that ships and yours takes over everywhere, including the pass or fail the command-line analyser reports, and deleting your file brings the original back.
Colour works the same way. Thirteen things on screen have a colour of their own — the meter track, the readout, the colour that means over the limit — and there is a picker for each: the canvas repaints while you drag, and any tablet mirroring the session repaints with it. Each colour tells you how well it reads against the panel behind it, so you find out that your meter track is nearly invisible before you are on a dark stage looking for it.
{
"id": "house-standard",
"name": "House standard",
"lufs_target": -12.0,
"lufs_tolerance": 0.5,
"true_peak_max": -1.0,
"lra_max": 14.0,
"odr_i_min": 8.0,
"odr_s_min": 6.0,
"vu_reference": -18.0
}Installing
Price: free. No paid tier, no trial, no account and nothing to unlock — every download below is the whole application, the plugin and the command-line analyser included. It measures up to eight channels, mono through 7.1.
| Platform | Download | Plugin | Note |
|---|---|---|---|
| macOS 14.2+ | .pkg | VST3 + AU | Universal — Apple silicon and Intel |
| Windows 10 1809+ | .exe | VST3 | Uninstaller in Installed apps |
| Linux | .tar.gz | VST3 | install.sh, no root |
| Linux | .AppImage | — | One file, no root, GTK from the host |
| Linux | .flatpak | — | Sandboxed, carries its own runtime |
| Any | oaa CLI | — | The file analyser, for a terminal |