10 Best Free Decibel Meter Apps for iPhone
Updated November 8, 2026 · written by AppHunt
A decibel meter app listens through the iPhone's microphone and turns the signal into a sound pressure level, the dB figure on the screen. Most offer frequency weighting: A-weighting (dBA) plays down deep and very high pitches the way the ear does and is the scale hearing-safety limits use, while C and Z keep more of the bass. Time weighting, fast, slow or impulse, sets how quickly the number moves. Built-in mics differ by model and run out of headroom somewhere past 100 dB, so the better apps let you calibrate against a reference meter or use an external microphone. Here is how ten free ones compare.
Decibel Meter Sound Detector
A plain, quick meter from an individual developer. It reads sound through the phone's microphone with A, B, C or Z weighting, shows current, average and top values along with the dominant frequency, and splits the sound into third-octave bands. You can record sessions and send the numbers by message or email. The developer says plainly that a phone mic is no substitute for lab gear.
Good for: Quick readings with octave-band detail
Keep in mind: The listing doesn't spell out what is free. It shows several purchases named Decibel Meter or Decibel Meter Premium, from $1.99 to $29.99 (US App Store, November 8, 2026; may change), and a release note mentions adding features to the free version. Reviews from 2024 to 2026 call it free, one says it has no ads, and one recent review complains that the max reading can't be reset. Last updated May 2025.
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Decibel
A meter that has grown into a toolkit. Next to the live dB reading you get a spectrum analyzer with FFT, spectrogram and octave-band views, a sleep mode that spots snoring, coughing and talking and places them on a night timeline using on-device recognition, and level overlays for photos and video. Each measurement can carry a place and a label and can go to Health.
Good for: Sound levels plus spectrum and night noise
Keep in mind: The developer calls its subscriptions optional and says they add the advanced analyzer and weighting tools, external microphones, unlimited saving and export, and video overlays. The listing shows many purchases, from $1.99 to $49.99, including a $9.99 subscription and a $19.99 Pro unlock (US App Store, November 8, 2026; may change). 2026 reviews say a trial offer opens first and can be skipped to the free meter; one says saving videos now needs payment.
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NIOSH SLM
Built with the US National Institute for Occupational Safety and Health; the one to pick for workplace noise. Besides the live level it reports LAeq, maximum and peak, a time-weighted average and noise dose under NIOSH and OSHA rules, in A, C or Z weighting. Its accuracy was tested against reference meters in a NIOSH lab, it accepts calibration and outside mics, and explains how to protect your hearing.
Good for: Workplace noise, dose and hearing safety
Keep in mind: The developer says it is completely free, with no ads and nothing locked, and the listing shows no in-app purchases. Since a spring 2026 update the app needs a 48 kHz microphone; several reviewers found it stopped measuring while Bluetooth hearing aids were connected and worked again with Bluetooth off. A March 2026 review says saving as PDF crashed.
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Decibel by AppRover
A simple meter with a chart of everyday sounds beside the reading, so you can tell whether a noise is nearer a chat, a diesel truck or something far louder. It supports A, B, C and Z weighting, shows the spectrum moving as you measure, and keeps a list of past sessions. Reviewers like that it opens straight to the meter and asks for no account.
Good for: Comparing a reading with everyday sounds
Keep in mind: The listing doesn't say what is free; it describes a Premium subscription with a free trial at $4.49 a month or $16.99 a year (US App Store, November 8, 2026; may change). 2026 reviews say live measuring works without paying and that saving records does not. It has not been updated since May 2020, and reviews from 2021 complain about subscription prompts.
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Sound Meter (Decibel)
Bare-bones and free: a gauge with the current level, a line graph, the low, mean and peak values, and a label saying what kind of sound the number compares to. Past measurements can be saved to a list. The developer itself warns that phone mics are tuned for speech and may not register sounds above about 110 dB, so treat it as a rough guide.
Good for: A no-cost gauge for quick checks
Keep in mind: No in-app purchases are listed, so there is nothing to buy; the app carries ads instead. October 2026 reviews complain about a banner at the bottom and pop-up ads, one of them inappropriate, and several 2026 reviews say quiet rooms read too high, though one reviewer says it can be adjusted.
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Decibel Meter Master
About as simple as a meter gets: open it and the noise level appears on one screen, with a word label that moves from quiet towards disturbing and dangerous. There is nothing to configure. It is an old app, last updated in 2018 for iOS 9, yet a September 2026 review says it still works with no charges and no ads.
Good for: A one-screen meter with nothing to buy
Keep in mind: No in-app purchases are listed and the developer doesn't describe a paid version. Expect a dated look; reviews from 2023 to 2025 say readings run high or sometimes don't appear, and one 2023 review says the app pushed shopping links.
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Decibel Meter Ultra
Set up like a professional meter: A, C and Z weighting, fast and slow time weighting and a separate peak reading, plus a dosimeter with NIOSH or OSHA profiles or one you define. Band analysis down to twelfth-octave steps helps when tuning speakers, and you can put levels over live video or build a PDF report. Outside mics work once calibrated against a reference.
Good for: Pro-style metering and speaker tuning
Keep in mind: Per the developer, the free plan includes the built-in metering profile and recordings of up to two minutes; PRO adds the rest, including custom profiles, charts, PDF reports, background recording and recordings of any length. PRO prices in the listing run from $7.99 to $59.99 (US App Store, November 8, 2026; may change). Several 2026 reviews complain of weekly or yearly charges they didn't expect, so check what you agree to before starting a trial.
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Decibel Meter dB
A straightforward meter: a large live dB figure with a short line on what that level means, and a scrolling timeline along the bottom so you can watch the noise rise and fall. Calibration for your microphone, frequency weightings and a full-screen view are sold as small unlocks. Musicians and band students in the reviews use it to keep their volume in check.
Good for: Watching volume change over time
Keep in mind: The listing doesn't say what is free. Purchases include weekly access at $3.99 or $4.99, yearly at $19.99 or $49.99, and unlocks for frequency weightings ($2.99), custom calibration ($1.99) and full-screen mode ($1.99) (US App Store, November 8, 2026; may change). Reviews mention ads and an unexpected $8.99 weekly charge, while others say they use the meter without paying.
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Decibel Meter by Devnex
The clearest about the free/paid split. Without paying you get a live level with current, lowest, average and highest values, a history graph, a manual calibration offset and playback of what you record. The developer calls the readings estimates and says the mic is used only during a measurement. Paying removes ads and adds response-time and weighting options plus saved history.
Good for: Free basics with a clear free/paid line
Keep in mind: The developer lists its free and premium features separately. Premium is a subscription: $1.99 or $3.99 a week, $2.99 a month or $9.49 for six months (US App Store, November 8, 2026; may change). Reviews from 2021 to 2023 complain about full-screen ads and purchase prompts, and a 2025 review says recordings couldn't be saved for free.
View in the App Store
Decibel Shield
A tidy meter that keeps a dated log of every session and can tag each one with where you took it. Alongside the live reading it shows the session's peak and average, a VU-style needle and a trends view that sums up your readings over days or weeks. It can keep measuring in the background, save levels to Health and also play white, brown or blue noise.
Good for: Logging noise by time and place
Keep in mind: The developer describes it as a free app. Premium is a subscription that may start with a 7-day trial: $1.99 a week, $4.99 a month, or $44.99 or $49.99 a year (US App Store, November 8, 2026; may change); the listing doesn't say which features it adds. 2026 reviews say the meter works without paying, though one complains of upgrade prompts everywhere and one of a charge that wasn't refunded.
View in the App Store
Questions and answers
Is there a free decibel meter app with no ads or subscription?
Yes. NIOSH SLM, from the US National Institute for Occupational Safety and Health, costs nothing, shows no ads and has no in-app purchases, and it is also the most thoroughly tested app here. Decibel Meter Master lists nothing to buy either, but it has not been updated since 2018. Sound Meter (Decibel) has no purchases and pays for itself with ads. The rest are free to use for live readings and charge for extras, and several show an upgrade or trial screen when you first open them, which you can close.
How accurate is a sound meter app on an iPhone?
Closer than you might expect, within limits. In NIOSH lab tests the better iPhone apps stayed within about 2 dBA of a reference meter, and NIOSH SLM states that figure for itself. The weak points are the microphone, which is made for speech and differs between models, very quiet rooms near the mic's own noise, very loud sound above roughly 100 to 110 dB, and wind or a thick case. A calibrated sound level meter app means you have matched it to a reference meter or a calibrator, which NIOSH SLM, Decibel Meter by Devnex and others allow. An external measurement microphone helps most; NIOSH reports that its app met Type 2 requirements of the IEC 61672-3 standard with one. For legal or compliance readings, use a certified meter.
Is the NIOSH Sound Level Meter app free, and who makes it?
It is free, with no ads and no in-app purchases. The app comes from NIOSH, the research institute for workplace safety and health that is part of the CDC, and it was built together with EA LAB, the acoustics company shown as the seller on the App Store. It measures LAeq, maximum and peak levels, time-weighted average and noise dose under NIOSH and OSHA rules, lets you calibrate, and includes guidance on hearing protection. If it reports a microphone problem, reviewers say turning off Bluetooth, for example for hearing aids, fixes it.
Can an iPhone or Apple Watch measure decibels without an app?
An Apple Watch can: its built-in Noise app measures the sound around you and can notify you when the level stays high for a while, and the readings go to the Health app. The iPhone has no such meter for the room. The Hearing control you can add to Control Center shows how loud the audio in your headphones is, not the noise around you. So without a watch you need an app, and many apps here, NIOSH SLM, Decibel and Decibel Shield among them, can save their readings to Health next to the watch data.
What does a decibel chart of common sounds look like?
Rough typical levels: a whisper about 30 dB, normal conversation about 60 dB, heavy city traffic about 85 dB, a lawn mower or a motorcycle about 90 dB and up, concerts and sports crowds often 100 to 110 dB, sirens around 120 dB, and fireworks or gunshots 140 dB or more. NIOSH sets 85 dBA averaged over eight hours as the level where long exposure starts to risk hearing damage, and every 3 dB louder halves the safe time, so 88 dBA is four hours and 100 dBA about 15 minutes. The decibel scale is logarithmic, so 10 dB more is ten times the sound energy.
What is the difference between dBA, dBC and dBZ?
They are frequency weightings. dBA cuts back low and very high frequencies roughly as human hearing does, and it is the scale used for hearing-safety limits and most noise rules. dBC is much flatter and keeps the bass, so it suits loud music, subwoofers and peak readings. dBZ applies no weighting at all. For checking whether a place is safe for your ears, use dBA; for measuring bass from a car stereo or a club, dBC tells you more.
Is Decibel X free?
It is free to download, but we could not confirm that you can use it for free. The listing doesn't say which features are free and sells a membership at $1.99 a week, $5.99 a month or $49.99 a year (US App Store, November 8, 2026; may change). Many 2026 reviews say a subscription or trial screen is the first thing you see and that it is hard or impossible to get past without signing up, and others report charges after a short trial. That is why it is not on this list, even though it has by far the most ratings of any sound meter in the US store.
How is the list ordered?
Places 1–10 are ordered by the number of ratings each app has in the US App Store, one app per developer. Only apps that are mainly sound level meters and let you measure decibels for free with no time limit qualify; trial-only apps and apps that keep the meter behind a subscription are left out. No app of ours is on this list. A rating count shows how widely an app is used rather than how accurate it is, so for work measurements NIOSH SLM's lab testing matters more than its place.