# Decibel Meter Online - Sound Level Meter with A/C Weighting

> Free online decibel meter: measure noise with your mic in real time, A/C/Z weighting, fast/slow response, min/max/average/Leq, 60-second graph and calibration.

- URL: https://qilingtools.com/en/audio/decibel
- Category: Audio Tools (https://qilingtools.com/en/audio)
- Tags: [Audio](https://qilingtools.com/en/tags/audio), [Physics](https://qilingtools.com/en/tags/physics), [Recording](https://qilingtools.com/en/tags/record)
- Last updated: 2026-10-26
- Price: Free, no sign-up
- Privacy: Runs locally in the browser; files are never uploaded

How loud is the construction upstairs, the traffic outside, your office or your bedroom at night? Open the page, allow the microphone and get a live sound level reading. It works like a real sound level meter: the raw microphone signal passes through A, C or Z frequency weighting (the IEC 61672 analog filters converted with a bilinear transform, within class 1 tolerance from 10 Hz to 20 kHz), then fast (125 ms) or slow (1 s) exponential time weighting, while the minimum, maximum, average and the energy-averaged equivalent level Leq are tracked. A 60-second graph with an 85 dB warning line shows how the level changes, and a reference chart of everyday sounds — whisper, office, traffic, subway, concert — highlights the one closest to your reading. When Leq exceeds 85 dB(A), the NIOSH-recommended daily exposure time is shown. Phone and laptop microphones are not calibrated, so the meter converts digital full scale (dBFS) to sound pressure level with a default +100 dB offset; drag the offset or calibrate in one step against a professional meter, and the value is saved in your browser. Browser auto gain, noise suppression and echo cancellation are turned off to keep the reading linear, and everything is computed on your device — nothing is recorded or uploaded.

## How to use

1. Click Start measuring and allow microphone access
2. Choose A/C/Z frequency weighting and fast/slow time weighting; calibrate if you have a reference reading
3. Read the live level, statistics, 60-second graph and reference chart, and reset the stats whenever you like

## Features

- A, C and Z weighting within IEC 61672 class 1 tolerance
- Fast (125 ms) and slow (1 s) time weighting
- Min, max, average and Leq
- 60-second level graph with an 85 dB line
- Calibration offset with one-step reference calibration, remembered
- Chart of typical sound levels
- NIOSH exposure-time guidance
- Auto gain and noise suppression off; computed locally

## FAQ

### How accurate is a decibel meter on a phone?

Treat it as an estimate. Phone and laptop microphones differ in sensitivity and frequency response, and the system may process the signal, so uncalibrated readings can be off by more than ±10 dB. Very quiet rooms (below 30 dB) run into the mic’s self-noise and very loud sources (above 100 dB) can clip. If you can borrow a professional meter, take one reading at the same spot and use Calibrate against a reference — relative changes will then be far more reliable.

### What’s the difference between dB(A) and dB(C)?

A-weighting mimics how the ear hears at moderate levels and strongly reduces low frequencies; it is the standard for environmental and workplace noise. C-weighting barely reduces the bass, so it suits music, low-frequency rumble and peaks. Z-weighting applies no weighting at all. Use A for general noise, and compare with C when bass or machinery hum is the issue.

### What is Leq and how is it different from the average?

Leq, the equivalent continuous sound level, averages the sound energy over the measurement and converts it back to decibels, so it represents the overall exposure and is what most noise regulations use. The plain average simply averages the decibel readings. Because decibels are logarithmic, occasional loud events push Leq well above the arithmetic average.

### How loud is too loud for my hearing?

NIOSH recommends no more than 8 hours a day at 85 dB(A), halving the time for every 3 dB: 4 hours at 88 dB, 1 hour at 94 dB and only 15 minutes at 100 dB. For sleep, a bedroom should ideally stay below 30–40 dB(A). The meter shows the allowed time whenever Leq goes above 85 dB(A).

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