How to measure sound with an online decibel meter
A browser meter is useful when you need a fast, repeatable comparison. It cannot certify a sound pressure level on its own. The guide below shows what the number represents, how to reduce common errors and when to use a calibrated instrument instead.
How do I get a repeatable reading?
Use the meter in the same way each time. A small change in distance, microphone direction or input settings can move the result. Let the five-second average settle before you compare one source, room or setup with another.
- Prepare the measurementKeep the device still, remove anything covering the microphone and choose one fixed position and distance from the sound source.
- Start the microphonePress Start dB and allow microphone access. Wait a few seconds for the input and five-second average to settle.
- Read and repeatRecord the current, average and peak estimates. Repeat with the same device, browser, position and calibration offset when comparing sounds.
Can an online decibel meter be accurate?
It can provide a useful estimate, but accuracy belongs to the complete measurement chain: microphone, device, browser processing, calibration, sound frequency and level. There is no honest universal error range for browser meters.
The NIOSH Sound Level Meter app is reported as accurate within ±2 dBA in NIOSH laboratory tests on supported iOS devices. That result applies to NIOSH's own tested system. It does not validate this website, every phone or every browser.
This meter requests that echo cancellation, noise suppression and automatic gain control be disabled. Browsers may fall back to their default input processing. A single calibration offset can align one steady reference level, but it cannot flatten an uneven microphone response or recover a clipped signal. See the full calibration and accuracy method.
Useful forQuick checks, teaching and same-device comparisons.
Not verified forHearing-risk, legal, medical or workplace-compliance decisions.
Best upgradeA calibrated external microphone or a type 1 or type 2 sound level meter.
What do dB, dB SPL, dBA and dBC mean?
The labels are not interchangeable. A plain number without its reference and weighting does not describe a professional sound-level measurement.
The decibel scale is logarithmic. NIOSH notes that a 3 dB increase doubles sound energy and a 10 dB increase represents ten times the energy. It is not valid to take the arithmetic mean of decibel readings.
- dB
- A logarithmic ratio. The reference quantity must be known.
- dB SPL
- Sound pressure level referenced to 20 micropascals in air.
- dBA
- An A-weighted level used in hearing-risk and occupational guidance.
- dBC
- A flatter weighting that retains more low-frequency sound and is often used for peaks.
- This meter
- An offset-adjusted, unweighted estimate from digital microphone amplitude.
How long can you be exposed to loud sound?
Level alone is not enough; duration matters. The table shows the NIOSH recommended occupational exposure limit: 85 dBA for eight hours, with recommended time halved for every 3 dBA increase.
| A-weighted level | Recommended duration |
|---|---|
| 85 dBA | 8 hours |
| 88 dBA | 4 hours |
| 91 dBA | 2 hours |
| 94 dBA | 1 hour |
| 97 dBA | 30 minutes |
| 100 dBA | 15 minutes |
Do not compare this browser reading directly with the table. The limits require a calibrated A-weighted measurement and describe occupational exposure. Use the noise exposure calculator only with an appropriate measured dBA value.
How does this decibel meter calculate its reading?
The browser supplies digital time-domain samples through the Web Audio API. dBmeter removes the sample mean, calculates root mean square (RMS) amplitude and applies 20 × log10(RMS) + calibration offset. The result is clamped to the display range from 0 to 130 dB.
This calculation maps digital amplitude to an estimated level after calibration. It is not a direct measurement of acoustic pressure and does not apply A- or C-frequency weighting.
- Current
- The latest valid RMS estimate.
- Average
- A five-second energy average, calculated before conversion to dB.
- Peak
- The highest displayed estimate since Start.
- Graph
- The microphone frequency spectrum from 20 Hz to 20 kHz.
When is a browser meter the right tool?
Use the required evidence, not convenience, to choose the instrument.
| Your task | Use this browser meter? | Better method when needed |
|---|---|---|
| Compare two rooms or sources with the same device | Yes, for a controlled relative comparison | Keep distance, direction and settings fixed |
| Check whether a change made a setup louder or quieter | Yes, when the microphone does not clip | Repeat the reading and compare the five-second average |
| Assess possible hearing risk | Screening prompt only | Use a calibrated A-weighted meter and time-based guidance |
| Document workplace compliance | No | Use a compliant sound level meter or personal dosimeter |
| Support a legal or neighbour-noise case | No | Follow local rules and use the specified calibrated method |
Questions people ask about decibel meters
Short answers to the points that cause the most measurement errors.
Can I measure decibels with my phone?
Yes, a phone can estimate sound level for quick comparisons. Accuracy depends on the microphone, browser processing, calibration, sound frequency, distance and whether the input clips. Use a calibrated sound level meter or dosimeter when the result affects health, work, legal or compliance decisions.
How accurate is an online decibel meter?
There is no universal accuracy figure for browser meters. This tool has not been validated as a complete device-and-browser system, so its reading is an estimate. NIOSH reports ±2 dBA for its own tested iOS app, but that result does not apply to other apps or to this website.
Why do two phones show different decibel readings?
Phones use different microphones, frequency responses, gain settings and audio processing. Cases, dirt, wind, microphone direction and distance also change the input. A calibration offset can align one steady reference level, but it cannot correct every frequency or prevent clipping.
What is the difference between dB and dBA?
A decibel is a logarithmic ratio. Sound pressure level in dB SPL uses 20 micropascals as its reference pressure. dBA is an A-weighted sound level that reduces some low-frequency contribution to better represent hearing risk. This browser meter does not apply A- or C-weighting.
What decibel level is too loud?
Risk depends on both level and duration. NIOSH treats repeated occupational exposure at 85 dBA over eight hours as hazardous and halves the recommended duration for each 3 dBA increase. Those limits require a calibrated A-weighted measurement, not this unweighted browser estimate.
How do I calibrate this decibel meter?
Place your device beside a trusted reference meter, expose both microphones to the same steady sound and adjust the calibration offset until the readings agree. Keep the device, browser, microphone, position and input settings unchanged for later comparisons.
Does dBmeter record or upload microphone audio?
No. Microphone samples are analyzed in your browser to calculate the live values and graph. The audio is not uploaded or stored by dBmeter. Your browser may save the calibration offset on this device.
Why is the decibel meter not working?
The meter needs HTTPS, a compatible current browser and microphone permission. Check the browser site settings, confirm that a microphone is connected and not muted, close other apps that may hold the input, then reload and press Start dB again.
Sources and editorial responsibility
dBmeter is maintained by ETF Nordic. The method is checked against the implementation, and claims on noise exposure or instrument behavior link to primary technical sources. Send corrections or reproducible device results to etfnordic@gmail.com.
Measure from the same position. Compare with the same setup.
Use the five-second average for repeatable checks, then read the accuracy guide before you rely on the result.