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SoundActivity: user guide

How SoundActivity is laid out: the three modes, finding a tool, calibration, recording and exports, guided workflows, nodes and the Coach.

What SoundActivity is

SoundActivity is a collection of tools for working with sound on an Android phone or tablet. It listens through the microphone and measures what it hears, it plays test signals through the speaker or headphones, and it analyses audio files you already have.

The tools are sorted into three modes:

  • Live measures the sound around you as it happens: level, spectrum, pitch, loudness, noise, distortion and more.
  • Generate plays signals: tones, sweeps and noise. Many of its tools play a signal and measure the answer at the same time, which is how a room, a loudspeaker or your own hearing is tested.
  • Offline opens a recorded audio file and analyses, compares or edits it without using the microphone.

This guide explains how the app is laid out and how the parts work together. Every single tool has its own page in the app's Help.

First start: the setup wizard

The first time you open the app, a setup wizard leads you through a few pages: the language, a profile that says what you mainly use the app for, the permissions for the microphone and for notifications, the audio settings, a test of your device's microphone and speaker, calibration, and a summary. Each page has a Skip button, and Skip All on the first page takes you straight into the app.

The microphone permission is the only one the tools cannot do without. Android asks for it once.

The top bar and the three modes

Under the app's name runs a row of seven icons:

  • Home opens a start screen with six large tiles: Live, Offline, Generate, Nodes, Guided workflows and Help.
  • Live, Offline and Generate switch the mode. The bar changes colour with it: teal for Live, purple for Offline, green for Generate.
  • Split view shows two live tools at once, one above the other.
  • Catalogue lists every tool (see the next section).
  • Nodes opens the screens for working with a second device (see Nodes).

Below the icons, the tools of the current mode are tabs that you swipe through.

The line under the app's name shows the input in use, for example "Input: Default mic". Tap it to choose another input, such as a USB microphone.

The small icons at the top right start a guided workflow, add an annotation, show the performance panel and list the tools you used recently. The three-dot menu holds the settings, the help, the device manager, the changelog and the legal texts. Which icons are shown, and in what order, can be changed in Settings under Appearance.

How to find a tool

There are 87 tools in Live, 41 in Generate and 34 in Offline, so swiping through tabs is not always the quickest way.

  • Catalogue: a searchable list of all tools. Type a word, or filter by mode and by one of 13 categories: Processing, Spectrum, Loudness, Voice & Pitch, Stereo & Phase, Room & Acoustics, Generators, Hearing tests, Calibration, Recording & Files, Diagnostics & Health, Music and Workflows. Each entry says in one line what the tool is for. Tap it to go there.
  • Profiles: a profile puts the tools of one kind of work first. There are 14, among them Sound Engineer, Acoustic Consultant, Musician / Producer, Podcaster / Content Creator, Home Theater / AV Enthusiast and General (all tools). In Settings you choose the profile and how strict it is: show all tools, show the profile's tools first, or show only the profile's tools.
  • Recent tools: the history icon in the top bar lists the tools you used last.

Running a tool, also with the screen off

Most tools have a Start and a Stop button. While a tool is running, Android shows a permanent notification, "Audio session active". It means the app may keep measuring or playing when the screen is off or when you switch to another app. The notification goes away when the last running tool is stopped.

Calibration: what the numbers mean

A phone's microphone is not a measuring instrument. Out of the box, SoundActivity shows levels relative to the loudest sound the device can record. To read real sound pressure levels, the app has to be told how sensitive the microphone is:

  • Calibration offset: compare the app's reading with a sound level meter you trust and enter the difference in the settings.
  • Calibration Wizard (in Generate): takes you through calibration with a reference sound source step by step.
  • Calibration files: measurement microphones come with a file that describes their frequency response. The app imports such files (miniDSP, REW and Dayton formats, and plain two-column tables) and applies them to the matching input.
  • USB microphones: a USB measurement microphone or audio interface can be plugged in and chosen as input. The app remembers the device and its calibration.

At the top of a measuring tool, a badge says how far the reading can be trusted, with an uncertainty in decibels: wider for an uncalibrated phone microphone, narrower for a calibrated setup.

Even calibrated, SoundActivity is not a certified sound level meter. Its results are for information. Where the law asks for a certified measurement, they do not replace one.

Recording, annotations and exports

Recording. Several Live tools write sound to the app's storage:

  • Recorder records a clip when a condition you set is met.
  • Rolling Buffer keeps the last 15, 60 or 120 minutes in 30-second pieces, so that a sound that already happened can still be saved.
  • Alerts watches the level and, when it stays above your limit for the time you set, records, shows a notification, or both.
  • Logger and Long Logger write down levels over time as numbers.
  • Session recording stores the sound together with pictures of the tool, to be played back later with Session Replay in Offline.

Annotations. The camera icon in the top bar attaches something to what you are measuring: a note, a photo from the camera or the gallery, a voice memo of up to a minute, or a picture of the tool as it looks at that moment. The Annotations tool in Offline lists them.

Exports. Tools export their results as PDF reports, as CSV tables, or as audio files; the Generator can save its signal as a WAV file. An export opens Android's share sheet, where you choose where the file goes. With an export the app also writes a SHA-256 checksum, so that a file can later be shown to be unchanged.

For reports, the settings take your name and role and, if you like, a company name, address and logo. They then appear on exported reports.

Guided workflows

A guided workflow is a list of steps for one job. It shows only the tools that job needs, says at each step why it matters, collects the results and ends with a summary.

Sixteen workflows come with the app: Room & Space Acoustics, Music Production & Mixing, Voice & Speech Analysis, Environmental Noise Monitoring, Industrial & Machinery, Audio Investigation, Research & Education, Hearing & Audiology, Audio Hardware Testing, Legal & Compliance Evidence, Live Sound & Venue, Audio Restoration, Podcast & Voice Content, Home Theater Calibration, Wildlife & Bioacoustics, and Classroom & Education Acoustics. You can also write your own in the workflow editor.

Start a workflow from the compass icon in the top bar or from the Guided workflows tile on the Home screen. The tools work the same inside a workflow as outside it.

Working with recorded files

In Offline mode you open an audio file through Android's file picker. The app reads what Android itself can decode, among them WAV, MP3, AAC, OGG, FLAC and M4A.

Some of what you can do with a file:

  • look at it: File Analyzer, Stereo Field, Onsets, Silence Map, Piano Roll;
  • compare two files: Two-File Compare, Cross-Corr, Spectral Sim, Before/After;
  • clean it up: Preprocessing builds a chain from de-hum, de-noise, de-click, de-reverb, a noise gate, dynamic EQ and corrective EQ; Declip repairs clipped peaks;
  • change it: Audio Editor (trim, fade, gain, normalise), Offline EQ, Loudness Norm, M/S Encoder, Freq Transpose;
  • work through many files at once: Batch Analysis and Batch Process.

Preprocessing also exists in Live mode, where the chain works on the sound from the microphone while you listen.

Nodes: using a second device as a microphone

A node is a second device that lends its microphone over the network. It can be another phone running SoundActivity with Node Mode switched on, or a Raspberry Pi running the node software. Your own phone, the controller, then measures what the node hears. Nodes are optional; without them every tool works with the phone's own input.

Pairing. Open Nodes, then the Node Manager. Nodes on the same network appear in a list by themselves. If the network hides them, enter the node's address by hand. Tap a node and type the four-digit PIN that the node shows. After that the node appears among the paired nodes and can be chosen as an input.

Your phone as a node. In the Node Manager, switch on Node Mode. The app asks for the microphone and notification permissions if it does not have them, shows the PIN, and keeps the microphone open with a permanent "Node Mode" notification. Stop it from the notification or with the same switch.

Mind the network. The connection between controller and node is not encrypted in this version, and while Node Mode is on, a device on the same network that has the PIN can listen to the phone's microphone. Use nodes on a network you trust, and switch Node Mode off when you are done. The privacy policy lists exactly what a node announces and sends.

With several paired nodes, the multi-node screens can start a measurement on all of them together and collect the results in one report. Some of this, such as recording sessions on the node itself, needs a Raspberry Pi node; a phone in Node Mode offers live values and live sound.

The Coach: results explained in plain language

The Coach is an optional helper. When it is on, a small lightbulb appears beside a tool's result. Tap it, and a sheet opens with four parts: What I see, Why it matters, What to do, and Confidence. "What I see" and "Confidence" repeat what the tool measured. The two parts in between are written by a language model that runs on your device.

To use it, open Settings, About, Coach, turn it on and download one of the models. They are large files: about 660 MB for Gemma 3 1B, about 1.6 GB for Qwen 2.5 1.5B and about 3.9 GB for Phi-4 Mini, which needs a device with at least 6 GB of memory. The app offers only the models your device has enough memory for, and by default downloads over Wi-Fi only. "Remove model" deletes the file again.

A small language model can be wrong, and it can word things oddly. The app marks Qwen 2.5 1.5B as experimental because it may make up measurement values. The line "What I see" always shows the real measurement.

Languages, help and widgets

  • Languages: English, Czech, German and French. The app follows the device's language or the one you pick in Settings under Appearance.
  • Theme: light or dark.
  • Help: the app's own Help has about 300 entries in nine groups, one for nearly every tool and setting, and opens at the entry of the tool you are in. From its menu the whole help can be exported as a Markdown or PDF file.
  • Widgets: six widgets can be put on the home screen: SPL Meter, Noise Dose, Logger, Calibration Status, Alert Status and Recording Status.

Hearing and voice tools are checks, not diagnoses

SoundActivity has tools that test hearing (Hearing Test, Audiometry, Tinnitus, and others) and tools that describe a voice (Voice Metrics, Voice Health, and others). They run on an ordinary phone with ordinary headphones, whose loudness the app cannot know exactly. Take their results as a first look. They are not a medical examination and do not replace one. If a result worries you, see a doctor or an audiologist.