Decibel, vibration & heart rate — phone sensor meters

Measure noise in dB — the reference table

The sound meter samples your microphone and computes sound pressure in decibels, updating live as the room gets louder or quieter. To read a number, you need context, so keep this reference nearby:

Everyday sound sits well below the danger line, but concerts, power tools and traffic push past it fast. The meter shows the current level plus a running peak, which is the part that matters when a sound spikes and settles before you can react.

• 30 dB — a quiet library or bedroom at night.
• 60 dB — normal conversation at arm's length.
• 85 dB — heavy traffic; the level where prolonged exposure starts to risk hearing.
• 100 dB — a motorbike, blender or subway platform.
• 120 dB — a loud concert or a siren up close, near the pain threshold.

What noise level is harmful, and how accurate is a phone?

Sustained exposure above roughly 85 dB is where hearing damage begins, and the risk climbs steeply from there — every few decibels up roughly halves the safe listening time. So a reading of 90 dB at a gig is not just "loud", it is a signal to move back or wear plugs. The sound meter is built to flag exactly that band.

Be honest about accuracy: a phone microphone is tuned for voice, not for lab measurement, so treat readings as a solid guide rather than a certified SPL value. Two phones can differ by a few dB, and very loud sounds can clip the mic. For a rough safety check or comparing two rooms it is genuinely useful; for compliance work you still need a calibrated meter.

Nothing is recorded or uploaded

A microphone tool naturally raises a privacy question, and the answer is the point: the sound meter measures the loudness of incoming audio and throws the audio itself away. Nothing is recorded to a file, and nothing is uploaded to a server — the mic stream is turned into a dB number on your device and then discarded frame by frame.

That matters because most "free" meters monetise through data or push you to a subscription for basic features. Carbide's meter has no account, no recording and no cloud step, so you can point it at a meeting, a nursery or a noisy neighbour without leaving a trace of what was actually said in the room.

Seismograph mode — measure vibration

The vibration meter reads your phone's accelerometer and plots motion over time like a seismograph, so shaking becomes a live waveform you can watch and screenshot. Set the phone on a surface and the trace stays flat until something moves it — then the amplitude of the line tells you how strong the vibration is.

Practical uses are everywhere: rest it on a washing machine to see if the drum is balanced, sit it on a car engine to spot a rough idle, or leave it on a desk to log a passing truck or a faint tremor. Keep expectations honest — it is a phone accelerometer, not a certified seismometer, so it reads relative shaking well but will not give you a scientific magnitude.

Check your pulse with the camera and flash

The heart rate monitor uses photoplethysmography, or PPG: you cover the rear camera with a fingertip, the flash lights the tissue, and the app watches tiny colour changes as blood pulses through your finger. Each pulse is a beat, and counting them over a few seconds gives beats per minute — no watch or chest strap needed.

To get a clean reading, press your finger gently but fully over both the lens and the flash, hold still, and wait about fifteen seconds while the trace settles. A resting adult pulse is usually 60–100 bpm. Important: this is a wellness feature, not a medical device — it is not a substitute for a certified monitor or an ECG, and anything worrying should go to a clinician, not an app.

Why these live on your phone, not the web

All three meters depend on hardware a browser tab cannot reach reliably or at all — a calibrated microphone stream, the raw accelerometer, and camera-plus-flash control for PPG. That is why they ship in the Carbide app for Android and iOS (coming soon) rather than as web tools, and why the measurements stay entirely on the device.

If you want to keep the results, pair them with tools you already have on the web: time a noise test or a pulse count with the stopwatch, and cross-check what sensors your handset actually has with device info. One toolkit covers the sensor jobs so you are not juggling a separate installer, and separate tracker, for each one.

Frequently asked questions