Noise Meter

What a noise log records

A noise log is a recording of sound levels over time. The Meter takes one level per second and keeps it in this browser. You choose how long the log runs and a threshold, the level you want to track. The summary then shows how often and how long the sound stayed above that threshold.

A single reading shows one moment. Most noise problems do not happen in one moment. A dog that barks for an hour, a truck on a nearby road, or a fan that cycles on and off can come and go all night. A log shows when the noise starts, how loud it gets, and how long it lasts.

When one reading is not enough

A single reading is fine for comparing two places or checking the sound next to you. Use a noise log when you need to know:

• Whether the noise happens at the same time each day or night.
• How much of a shift, a night, or a day the sound stays above a level.
• Whether the loud moments are rare or constant, and how quiet the quiet times are.

Use cases

Set the length and threshold for the question you are asking.

For the bedroom, WHO recommends an average under 30 dBA over the night for good sleep, and single events under 45 dBA. Set the threshold to 30 dBA to see how much of the night is above the guideline. Then check the Maximum against 45 dBA.

For work, the NIOSH limit of 85 dBA is an average over an 8 hour day, so the Leq for the shift is the number to compare. The time above 85 dBA shows where the exposure comes from.

Choosing a threshold

Start with the quiet background. Place the phone where you will log, and measure for 30 to 60 seconds while the room is quiet. Read Avg (Leq), then set the threshold a few steps above that level so only real rises are marked.

When a guideline applies, use it instead. The bedroom guideline is 30 dBA, single events in bed are 45 dBA, and a workday limit is 85 dBA. Thresholds move in 5 dB steps, and 5 dB is about three times the sound energy of the step below.

Avoid a threshold at or below the background. If the background is 42 dBA, a 40 dBA threshold marks almost the whole log, and the list of periods stops being useful.

Setting up a log

1. Place the phone. Put it on a stable surface with the microphone uncovered. The microphone is usually on the bottom edge. Stay away from walls, which push levels up, and away from your own noise, such as your voice or typing.
2. Plug it in. Long logs drain the battery. For a log of several hours, keep the phone charging.
3. Keep the screen on and the tab in front. Phones stop the microphone when the screen locks, and a background tab also creates Gaps. The site asks the browser to keep the screen on, but check that it stays on.
4. Set the weighting first. Choose dBA or dBC in Settings before you start. Weighting cannot change during a log.
5. Choose the length and threshold. Pick a length from 15 minutes to 8 hours, or no limit. Pick a threshold in 5 dB steps.
6. Start before the noise begins. A log that starts late misses the first rise, which is often the start of the pattern you want. Stop recording also stops the Meter.

Reading the summary

The summary covers the whole log. It includes these values:

• Graph: the level over the whole log, with Gaps and the periods above the threshold marked. A steady line means constant noise. Spikes mean events.
• Leq: the average level over the log. It is an energy average, so loud moments count more than quiet ones.
• L10: the level exceeded 10 percent of the time. It shows how loud the peaks are.
• L90: the level exceeded 90 percent of the time. It shows the background, the level that stays in the log most of the time.
• Maximum: the loudest level, with the time it happened.
• Time with no data: the part of the log with no levels, which is usually a Gap.
• Periods above threshold: the stretches when the level was above your threshold.
• Gaps: times when the screen was locked or the tab was in the background. Gaps are marked, not hidden, so a log with many Gaps covers less time than its length suggests.

A worked example

These numbers are made up to show how to read a summary. They are not measurements. The log ran for 2 hours from 11 pm, with the threshold at 45 dBA, from a bedroom window facing a street.

• Leq 41.2 dBA: the average over the night.
• L90 36.4 dBA: the background stayed near 36 dBA most of the time.
• L10 47.8 dBA: the peaks reached about 48 dBA for 10 percent of the time.
• Maximum 62.1 dBA at 12:08 am.
• Periods above 45 dBA: three, totaling 17 minutes. The longest ran from 12:05 to 12:19 am.
• Gap: 11:40 to 11:44 pm, with the screen locked. Time with no data: 4 minutes.

The 17 minutes above 45 dBA are about 15 percent of the 116 minutes with data. The 14 minute period after midnight is the one to compare with the street or a neighbor's schedule. The 4 minute Gap means that stretch is unknown, not quiet.

Using the CSV

Each saved log can be downloaded as a CSV. The file has timestamps, levels, and gap markers, so you can sort, chart, or filter it in a spreadsheet. Only the newest 10 logs are kept in this browser, so download the logs you need before newer ones push them out.

Limits

A noise log is a set of estimates from a phone microphone. It is not certified evidence. The phone is not a calibrated sound level meter, and the accuracy notes on the home page apply here too.

Local rules and authorities decide what counts. A city, a landlord, an employer, or a court may require its own method. A log cannot settle a dispute on its own.

A log is more convincing when it:

• Covers several nights or shifts, not one.
• Is measured from the same spot each time.
• Includes written notes of what you heard and when.
• Has few Gaps. Keep the phone unlocked and the tab open.

Privacy

The log stores levels only, never audio. The microphone signal is analyzed on your device and is never uploaded. There is no account. Saved logs stay in this browser.

To delete a log, remove it from the saved logs on the page. To remove them all, clear this site's data in your browser. Download any log you want to keep first.