You can try the whole Consentiva workflow before you buy any hardware. In test mode the phone's own microphone or sensors stand in for a receiver, so you get the real thing: a walk, a spectrum, marks, GPS, video, a report and a share link. It isn't radio, and every screen says so.
Two test modes
- Just my phone: try it first. Sweeps the microphone's sound spectrum from 0 to about 24 kHz, once a second, and records the phone's other sensors alongside.
- Just my phone: sensors only (no microphone). Sweeps the slow oscillation, 1 to 30 Hz, of the magnetic-field sensor on Android Chrome, or the accelerometer (vibration) on iPhone and Android. No sound is captured and the microphone is never opened.
What you can see
- Sound mode: voices, fans and air conditioning, traffic, the 60 Hz hum and harmonics of transformers and appliances, and ultrasound from some devices.
- Sensors mode: hold the phone near a motor, transformer, charger or router and watch which slow frequencies appear. Walk it past a vibrating machine and the vibration shows.
What you can't see
Radio. Wi-Fi, Bluetooth and cellular signals are invisible to a phone's microphone and sensors, and a web page can't read the phone's radios. iPhone Safari also doesn't offer a magnetometer, battery or network information. So a phone test shows that the workflow works, not what is on the air. To see radio, add an RTL-SDR stick or a HackRF to an Android phone.
Try it
- Open consentiva.xyz/app on your phone and sign in.
- Under Receiver choose Just my phone (sound) or sensors only.
- Tap Start walk, allow location, microphone (sound mode) and motion when asked, and walk.
- End the walk and open the report. It is labelled "Test data" and can be shared like any other walk.
How the sound spectrum is made
The phone records the microphone for about a second, and the app splits that second into frequency channels using a fast Fourier transform. Each channel is 50 Hz wide, from 0 up to about 24 kHz (half the usual sampling rate of 48 kHz). For each channel the app keeps two levels: the peak (the highest level seen during the second) and the average, in decibels relative to full scale (dBFS). Zero dBFS is the loudest level the microphone can represent, so normal levels are negative numbers. The audio itself is thrown away, and only these levels are kept.
Things to try
- Mains hum. Hold the phone near a transformer, a charger or a refrigerator and look for peaks at 60 Hz (or 50 Hz) and at multiples of it.
- Motors and fans. A steady fan makes a low tone and its harmonics. The pitch rises as the fan speeds up.
- Running water or traffic. Broad, noisy blocks across many channels rather than narrow peaks.
- Ultrasound. Some devices, such as ultrasonic pest repellers and some sensors, emit tones around 20 to 25 kHz. Many phones can see up to about 20 kHz or a little higher, depending on the microphone.
- Voices. Speech sits mostly between about 100 Hz and 4 kHz. Because the app does not save audio, a voice is only a pattern of levels, but be considerate of others when the microphone is on.
Sensors-only mode in detail
In sensors-only mode the app reads the phone's motion sensors and, where the browser allows it, the magnetic-field sensor. It samples them at about 60 times a second and builds a spectrum of how the signal changes from 1 up to about 30 Hz, in steps of half a hertz. A motor or fan creates a vibration at its rotation rate, so the accelerometer shows it when the phone rests on or near it. A magnetometer responds to changing magnetic fields near transformers, chargers and motors, and to the metal in vehicles and buildings.
Which sensors you have depends on the phone and browser. Android Chrome generally offers both a magnetometer and an accelerometer. iPhone Safari offers motion data after you grant permission, but not a magnetometer reading in a web page.
Permissions
- Location is asked for when the walk starts, so each reading has a position.
- Microphone is asked for only in sound mode. Sensors-only mode never opens it.
- Motion and orientation. On iPhone you have to allow "Motion & Orientation" when asked. On Android, make sure the site's "Motion sensors" setting in Chrome is not blocked.
Troubleshooting
| What you see | What to try |
|---|---|
| A flat spectrum in sound mode | The microphone permission was refused. Allow it in the browser's site settings and restart the walk |
| "This phone's browser isn't giving motion or magnetic sensor readings" | Allow motion access (iPhone), or unblock "Motion sensors" for the site in Chrome (Android) |
| Readings jump when you walk | That is normal: a phone in a moving hand is itself a vibration source. Hold it still for a clean reading |
| No GPS position | Allow precise location, go outdoors for a minute, and wait for the accuracy figure on the walk screen before you start walking |
From a test walk to radio
Everything you learn in test mode carries over: starting and ending a walk, marking, GPS, video, the report and sharing. The difference is the receiver. For radio, you plug a USB receiver into an Android phone with Chrome, choose it under Receiver, and the app records the real airwaves instead. See what to buy and the guides for the RTL-SDR stick, the Blog V4 and the HackRF.
Privacy
Consentiva measures sound levels only and never saves audio. Test walks are kept apart from radio walks, so they never change your baselines. Be mindful of where you carry a phone with the microphone on, and don't use test mode to listen in on other people. See the Privacy page.
Common questions
Can a phone receive radio signals on its own?
No. A phone's microphone and sensors measure sound, vibration and magnetic fields, not radio. To see real radio signals you add a USB receiver to an Android phone with Chrome.
Does it record audio?
No. Only a spectrum, one reading a second, is saved. The microphone's audio is never stored, and sensors-only mode never opens the microphone.
What does the sensors-only mode measure?
The slow oscillation, 1 to 30 Hz, of the phone's magnetic-field sensor where it has one (Android Chrome), otherwise of the accelerometer (vibration, on iPhone and Android).
Is the test data mixed with radio readings?
Never. Test walks keep their own baselines and are labelled test data, not radio, on reports and share pages.
Can the phone detect ultrasound?
Some can. Many microphones respond up to about 20 kHz or a little higher, so tones from ultrasonic devices around 20 to 25 kHz may show faintly or not at all, depending on the model.
Why doesn't my iPhone show the magnetic field?
iPhone Safari doesn't give web pages access to the magnetometer. Sensors-only mode uses the accelerometer (vibration) on an iPhone, and the magnetometer on Android Chrome where it is allowed.