Pocket Seismograph: Vibration

Version 2.0 names the frequency. The app now reports the dominant frequency of whatever it is sitting on, in Hz, with a full spectrum behind it, sampled at 100 Hz.

See how hard a surface is shaking, and at what frequency.

Pocket Seismograph reads your iPhone's accelerometer at 100 Hz, draws the vibration live, and names the strongest frequency it can find in it.

WHAT YOU GET

• Dominant frequency in Hz, with a full spectrum chart behind it
• Live trace with NOW, MAX, AVG and RMS, as magnitude or full XYZ
• Rotation-speed readout in rpm, offered as a hypothesis when the reading looks like a rotating part
• Estimated felt intensity and estimated peak ground velocity
• Three processing modes: Raw, Stable and Vibration
• Sessions you can name, tag, search and reopen
• CSV export through the system save dialog, with locale-aware profiles
• Calibration wizard that measures your own device's noise floor
• Works offline. No account, no sign-in.

GREAT FOR

• A washing machine that walks across the floor. A spin cycle sits around 17 to 27 Hz, and the app names it.
• HVAC units and fans: read the running frequency, then the rpm it implies.
• Floors, stairs and beams that move when someone walks past.
• Construction, traffic or machinery you want recorded with a timestamp.
• Feeling a tremor and wanting the next one captured.

HOW IT WORKS

1. Put the phone flat on the surface, screen up.
2. Press Start. Watch the trace and the frequency card.
3. Save the session, add a note, export CSV when you need to show someone.

WHAT IT WILL NOT DO

Frequency analysis reads reliably from about 1 Hz to 40 Hz, and only indicatively up to roughly 50 Hz. Vibration faster than half the sampling rate does not simply disappear, it folds back and can appear as a false low-frequency line. Amplitude is indicative: the case, how firmly the phone rests on the surface, and filtering inside the sensor itself all color the number. The frequency is the more trustworthy half of the reading.

When nothing stands clearly above the noise, the app says "No clear frequency" rather than inventing one. That is the correct reading for a phone lying still on a desk.

This is not a certified seismic instrument and it is not calibrated for legal evidence. It is not a medical or diagnostic device. It sends no seismic alerts, so for early warnings use your country's official system. It cannot see the 60 Hz to 500 Hz range where bearing and gear features live, so finding nothing here says nothing about them.

Available in 49 languages.

Built by an independent developer who thinks a measurement tool should tell you when it does not know. If it is useful to you, a review is the best thanks.