1. Open the Decibel Meter
Open the online decibel meter on the device you will measure with. It works on any phone, tablet, or computer with a modern browser — no app installation is required. The meter shows live dB, minimum, maximum, average, peak, RMS, and Leq, and runs entirely in the browser.
2. Allow Microphone Access
Click Start Measuring and accept the microphone permission prompt. The browser shows this prompt for every website — it is a privacy safeguard, not a warning. In this tool, audio is processed locally on your device and never uploaded or recorded.
If you accidentally deny access, use the padlock icon in the browser's address bar to re-enable the microphone for this site, then refresh. Some browsers require you to close and reopen the page after changing the setting.
3. Position the Device Correctly
Where you place the device determines what you measure:
- For room or background noise: put the device where people sit or stand — on a table, not held in your hand.
- For a specific source: point the microphone toward the source at the distance that interests you (for example, 1 meter from a speaker).
- For a comparison: measure from identical positions and distances in both locations.
- For workplace or home checks: measure at ear height, the way your ears actually experience the noise.
Knowing the microphone's location is often hidden in a small hole at the bottom edge of a phone. Many cases cover it — check before measuring.
4. Keep the Microphone Unobstructed
Anything that blocks the microphone port skews the reading — sometimes by 10 dB or more:
- Remove or reposition cases that cover the mic opening.
- Don't grip the phone over the mic port.
- Keep the screen (and your fingers) away from the mic when holding the device.
- Avoid measuring from inside a pocket or bag — that measures the pocket, not the room.
5. Maintain a Consistent Distance
Sound level falls by roughly 6 dB each time the distance to the source doubles (outdoors), so a few centimeters of movement changes the reading noticeably. Decide the distance once, and write it down with every result: "70 dB at 1 m" is a useful measurement; "70 dB" is not.
For steady sources, hold the device still for the whole session. Moving around while measuring mixes different positions into one average, which makes the result hard to interpret.
6. Measure for an Appropriate Period
A single instant is a snapshot — background noise fluctuates. Practical durations:
- 30 seconds: quick check for a steady sound (fan, appliance, hum).
- 1–2 minutes: room or traffic noise with moderate fluctuation.
- 5–15 minutes: anything with intermittent events (passing cars, doors, conversation, construction).
- Full period: for exposure-style questions, measure the entire period of interest. The noise exposure guide explains why duration matters as much as level.
Longer sessions make the average and Leq far more meaningful. The meter tracks duration automatically and shows the history chart so you can see how much the level varied.
7. Interpret the Results Carefully
Each statistic answers a different question:
- Current — the level right now; useful while you move around the room.
- Minimum — the quietest moment; a good proxy for background noise when the room is briefly still.
- Maximum — the loudest event; expect it to be much higher than the average if there are intermittent sounds.
- Average — the arithmetic mean of the session; the typical level.
- Leq — the energy-equivalent level for the whole session; the metric professionals use for exposure.
- Peak — the highest instantaneous pressure; relevant for impulse noise (bangs, impacts).
Compare your numbers against the common sounds chart to sanity-check them: a room that "feels" like a quiet library should read in the 30–40 dB range, not 60.
8. Repeat When Needed
One measurement is a sample, not a verdict. For anything that matters:
- Repeat at a second position and compare the averages.
- Repeat on a different day or time if the noise varies (traffic, neighbor noise, HVAC cycles).
- Repeat after changes — new furniture, a window closed, a fan turned off — to quantify the difference.
- Export the session (CSV or JSON) or save it to the Noise Journal so you have a record.
If readings seem implausible, read the accuracy guide — automatic gain control and noise suppression are the usual culprits — and calibrate the meter against a known reference for better consistency.
Common Mistakes and How to Avoid Them
- Covering the mic with a hand or case — the single most common error.
- Measuring from the couch or bed instead of where the noise matters.
- Trusting a 3-second reading — always let the meter run and use the average or Leq.
- Comparing two rooms measured at different distances — distances must match.
- Measuring while talking — your own voice adds 10–20 dB to the reading.
- Ignoring calibration — a 10-minute calibration session makes future readings comparable.
Following this workflow, a phone decibel meter is genuinely useful for checking rooms, speakers, appliances, and street noise. For certified results, use a calibrated sound level meter (IEC 61672 class) — see theaccuracy guide for when that is required.