User Manual & Help Center
Everything you need to get reliable readings out of Decibel Meter, plus answers to the questions we get asked most.
Quick Start Guide
1. Allow the Microphone
The first time you open the Measure tab, iOS asks for microphone access. Without it the app has nothing to listen to. If you tapped "Don't Allow" by accident, go to Settings > Privacy & Security > Microphone and switch Decibel Meter on.
2. Hold the Phone Properly
Keep your fingers, a thick case, and any lanyard away from the microphone at the bottom edge of your iPhone. Point the bottom of the phone towards the sound source, hold it still, and give it a second or two to settle before you trust the number.
3. Read the Level
The large number is the current sound level in decibels, and the graph underneath shows how it has moved over the last couple of minutes. It updates continuously — you do not have to start a recording just to see how loud a room is.
4. Pick a Weighting and Response Speed
A-weighting matches how human hearing responds and is what most noise regulations use — leave it on A unless you have a reason not to. Fast (125 ms) reacts quickly and is good for short bursts; Slow (1 s) smooths things out and is better for steady background noise.
5. Record a Session
Tap the record button to start a measurement session. While it runs, the app tracks the minimum, the average, the maximum and the peak level, along with your noise dose. You can pause and resume; when you stop, you can name the measurement and save it to your records.
6. Review It Later
Everything you save appears in the Records tab with its duration, its maximum level and, if you allowed location access, the place it was taken. Open any record to see the full graph and statistics again.
Understanding the Features
A, C and Z Weighting
These are the standard frequency weighting curves from IEC 61672. A de-emphasises very low and very high frequencies the way the human ear does, and is the basis of almost every noise limit you will encounter. C keeps much more of the bass, which is why it is used for loud music, machinery and peak measurements. Z is flat — no weighting at all — and shows the raw level across the spectrum.
Min, Average, Max and Peak
Min and Max are the quietest and loudest smoothed readings during the session. The average is an Leq — a true energy average, not a simple arithmetic mean, which is the correct way to summarise a noise level over time. Peak is the highest unsmoothed instantaneous value, so it is always the largest of the four.
Noise Dose
The dose percentage estimates how much of a full day's safe noise exposure you have used, based on the NIOSH recommendation: 85 dB for 8 hours, with a 3 dB exchange rate. Every 3 dB louder halves the safe time — 88 dB for 4 hours, 91 dB for 2 hours, and so on. 100% means you have reached the recommended daily limit.
Simple and Detailed Views
The simple view is just the number and the graph. Switch to the detailed view when you want the frequency spectrum and the dominant frequency — useful for identifying what is actually making the noise, such as a hum from a motor or a whine from a fan.
Camera Mode
Camera mode puts the live decibel readout on top of what your camera sees, and can record it as a video clip — handy when you need to show what was loud, not just how loud it was. The clip is recorded without an audio track, because the microphone stays dedicated to measuring.
Calibration
Settings > Calibration lets you match the app to a reference. Stand next to a meter you trust in a steady sound field, set the target to the value that meter shows, and save. The app averages its recent readings, works out the difference, and applies that correction to every measurement from then on. You can reset it to the factory default at any time.
Reference Table
Settings > Reference Table lists decibel bands with everyday examples, colour-coded from safe through caution to dangerous, so you can put a reading in context at a glance.
What the Numbers Mean
| Level | Sounds like |
|---|---|
| 0–30 dB | Whisper, quiet bedroom |
| 30–50 dB | Library, light rain |
| 50–65 dB | Conversation, office |
| 65–80 dB | Busy street, vacuum cleaner |
| 80–95 dB | Heavy traffic, hairdryer |
| 95–110 dB | Concert, power tools |
| 110–130 dB | Siren, jet takeoff |
Troubleshooting Common Issues
"The reading is stuck at zero or nothing happens."
- Permission: check Settings > Privacy & Security > Microphone and make sure Decibel Meter is enabled.
- Another app has the microphone: end any call, voice memo, or video recording running in the background, then reopen the app.
- Blocked microphone: a case, a screen protector overhanging the bottom edge, or a finger over the microphone hole will mute it. So will pocket lint — a soft brush usually fixes it.
"The readings look too high or too low."
- Calibrate: phone microphones differ from model to model. Use Settings > Calibration against a meter you trust to correct the offset once.
- Check the weighting: the same sound reads noticeably higher on C or Z than on A. Comparisons are only meaningful with the same weighting.
- Wind: even a light breeze across the microphone adds tens of decibels of noise that is not really there. Shield the phone outdoors.
"Very loud sounds seem to flatten out."
- iPhone microphones physically clip somewhere above roughly 100–120 dB, depending on the model. Beyond that the app cannot see any further increase.
- For anything that loud — concerts, gunshots, industrial machinery — treat the reading as "at least this loud" and use certified equipment if the number has to be exact.
"My recorded clip has no sound."
- That is intentional. Camera clips are saved without an audio track so that the meter keeps exclusive use of the microphone and the decibel readout stays accurate throughout the recording.
"My measurements have no place name."
- The place label needs location access. Enable it in Settings > Privacy & Security > Location Services > Decibel Meter, set to "While Using the App".
- Existing records keep whatever label they had when they were saved.
"I subscribed but the premium features are locked."
- Open Settings in the app and tap Restore Purchases.
- Make sure you are signed in with the same Apple ID you used to purchase.
- If it still does not unlock, email us the Subscription ID from Settings > Billing and we will sort it out.
Frequently Asked Questions (FAQ)
Q: How accurate is it?
A: For everyday comparisons — is this room louder than that one, is the music above 90 dB — it is genuinely useful, especially after calibration. But it is not a certified Class 1 or Class 2 sound level meter, and readings should never be used as evidence for legal, occupational or regulatory purposes. Accuracy depends on your device model, its microphone, your case and the environment.
Q: Does the app record my conversations?
A: No. A normal measurement analyses audio in short buffers and throws them away immediately — only the numbers are kept. Nothing is uploaded anywhere, and there is no speech recognition. See our Privacy Policy for the full detail.
Q: Does it work without an internet connection?
A: Yes. Measuring, saving and reviewing records all work fully offline. A connection is only needed to start or restore a subscription.
Q: Can it keep measuring while the screen is off or I'm in another app?
A: No. Measuring runs while the app is open and in the foreground, so the microphone is only ever in use when you can see that it is.
Q: What is the difference between dBA and dBC?
A: They are the same sound measured through different filters. dBA discounts the low frequencies your ear is less sensitive to, which makes it the standard for hearing-risk and noise-nuisance limits. dBC keeps the bass, so it reads higher for music, engines and machinery, and is the usual choice for peak levels.
Q: Why is the "average" different from the mid-point between min and max?
A: Because decibels are logarithmic. The app reports Leq, an energy average, which is the correct way to average noise over time. A few loud moments raise it much more than a simple arithmetic mean would suggest — which is exactly what you want when assessing exposure.
Q: At what level should I worry about my hearing?
A: As a general guide, sustained exposure above 85 dB is where risk begins, and every 3 dB above that halves the time you can safely spend there. The dose indicator in the app is based on that NIOSH guidance. It is general information, not medical advice — if you are worried about your hearing, see an audiologist.
Q: Where are my measurements stored?
A: On your device, inside the app. They are not synced to us or to any server. They are included in your iPhone backup, and deleting the app deletes them.
Q: How do I cancel my subscription?
A: Subscriptions are managed by Apple. Go to Settings > tap your name > Subscriptions on your iPhone, select Decibel Meter and cancel. Cancelling stops the next renewal; access continues until the end of the period you have paid for. Deleting the app on its own does not cancel anything.
Q: I want a refund.
A: Purchases go through Apple, so refunds are requested at reportaproblem.apple.com. We are not able to issue them ourselves, but tell us what went wrong and we will try to fix it.
Contact Support
Still stuck, or spotted something wrong? We read every message.
support@appcellent.co