Support
Decibel — Sound Level Meter
Getting Started
How do I measure sound?
Open the app and tap Measure on the dashboard. The meter starts reading the live dB(A) level immediately. Tap Start to begin a timed, named session, then Stop to save it. You'll see min, average, max, peak, and Leq the whole time.
What is Leq, and how is it different from average?
Leq (equivalent continuous level) is the steady dB level that carries the same total sound energy as the changing level over your session. Because sound energy is logarithmic, Leq weights loud moments more heavily than a simple average — it's the standard figure used for noise-exposure assessment.
When should I use dBA vs dBC vs dBZ?
dBA mimics how human hearing responds and is the standard for hearing-safety and noise-complaint measurements — use it by default. dBC keeps more low-frequency energy, useful for bass-heavy sound and peak levels (concerts, machinery). dBZ is flat/unweighted. dBA is free; dBC and dBZ are included with Premium.
Accuracy & Calibration
How accurate is the iPhone as a sound meter?
iPhone microphones are factory-calibrated, and independent testing has found well-built iOS meters land within about 2 dB of a professional Type 1 meter. Decibel captures audio in measurement mode (which disables automatic gain control) for stable readings. It is still a consumer tool, not a certified instrument — see the note below.
How do I calibrate the meter?
Open Settings and adjust the calibration offset (Premium). If you have access to a reference sound level meter or a known source, compare readings in a steady environment and nudge the offset up or down until Decibel matches. The offset is saved per device.
It reads high (or low) when it's quiet. Why?
A few dB of drift on an uncalibrated phone mic is normal, and a case covering the microphone, wind, or handling noise can inflate readings. Remove any case obstruction, hold the phone still with the bottom mic clear, and set a calibration offset (Premium) to dial it in.
Noise Exposure
What does the daily noise dose mean?
Your dose is the percentage of a recommended daily noise limit you've accumulated from your saved sessions. Decibel tracks both the NIOSH standard (85 dBA action level, 3-dB exchange rate) and the OSHA standard (90 dBA, 5-dB exchange rate). 100% means you've reached that day's recommended limit; sustained exposure above it raises the risk of hearing damage.
What are the loud-event alerts?
If you enable notifications, Decibel can warn you when sustained sound crosses 85 dBA — a prompt to move away or put in hearing protection. You can turn alerts on or off in Settings, and disable them entirely in iOS Settings.
Reports & History
How do I export a report?
Open any saved session and tap Export (Premium) to generate a CSV (for spreadsheets) or a PDF report with the level graph and summary statistics — useful for noise complaints, workplace records, or your own log. Share it via the iOS share sheet.
Do I need an internet connection?
No. Metering, dose calculation, history, and report export all run entirely on your device, even in airplane mode. The only network activity is ad serving on the free tier.
Free vs Premium
What's free vs Premium?
Free: the live dB(A) meter with waveform and full statistics, today's noise dose, and your last 3 saved sessions, with banner and interstitial ads (never on the live meter screen). Premium: unlimited measurement history, dBA/dBC/dBZ weighting, the microphone calibration offset, the full exposure timeline with charts, CSV/PDF reports, and zero ads.
Is there a free trial?
Yes — the Premium Annual plan ($24.99/year) includes a 7-day free trial. You'll only be charged at the end of the trial. Cancel anytime in your Apple ID subscription settings before the trial ends.
How do I restore my purchase?
Open Settings inside the App and tap "Restore Purchases". This re-applies your active subscription if you've previously purchased one on this Apple ID.
How do I cancel my subscription?
Open the iOS Settings app, tap your name at the top, then tap Subscriptions. Find Decibel and tap Cancel Subscription. Cancellation takes effect at the end of the current billing period.
Privacy
Does Decibel record what I'm measuring?
No. The app reads the live microphone signal only to compute sound levels, then discards the audio immediately — it's never saved or uploaded. What's stored is the measurement result (numbers and a level graph), all on your device. See the Privacy Policy for full details.
What permissions does the app need?
Microphone (required, used only while measuring) and Notifications (optional, for loud-event alerts and exposure reminders). That's it.
A Note on Accuracy
Decibel is not a certified Type 1 or Type 2 sound level meter and is not a medical or hearing-diagnostic device. For legal, occupational, or clinical decisions, use certified equipment operated by a qualified professional.
Contact Us
Email Support
For questions, bug reports, or feature requests:
We typically respond within 48 hours. If you're reporting an accuracy issue, telling us your iPhone model and whether you use a case helps us help you.