Decibel - Sound level checker

A precise, restrained sound meter for the room you're in. Real-time levels, calibrated to your phone, on-device only - no audio is ever recorded.

Decibel turns your iPhone into an ambient sound-level meter — a precise, restrained instrument for understanding the noise around you.

THE READOUT A single number, measured in real time and smoothed enough to actually read. The screen shifts colour with the level - green when quiet, amber at conversation, red when loud - so you feel the room before you read the value.

THE RECORDING Tap the red button to start a measurement session. Decibel tracks the peak and average dB along with a live 15-second waveform. Tap again to stop, and the session is saved to your local history with its timestamp, duration, peak, and average - no audio is recorded, only the summary.

THE INSTRUMENT

• Two-tier smoothing - a fast filter drives the bar and the background tint, a slower one keeps the headline number stable
• Calibration sheet - tune Decibel against a reference meter you trust, so readings match on your specific device
• Live waveform during recording, showing variation at a glance
• Recording history persists across sessions; swipe to delete or clear all
• Custom typography, dark-only design, full-screen meter, no distractions

ON-DEVICE, ALWAYS

• Audio is processed in real time and immediately discarded — no audio is recorded, stored, or transmitted
• Only summary statistics from recording sessions are saved (start time, duration, peak dB, average dB), to your phone's local storage
• No analytics, no tracking, no accounts, no advertising, no network requests
• No third-party SDKs

ON ACCURACY iPhone microphones are not laboratory-calibrated, so the values shown are estimates. Treat them as a relative measure - how loud one environment is compared to another - not as certified sound-pressure measurements.

Decibel is not suitable for hearing-safety decisions, OSHA or NIOSH compliance, medical assessment, or any purpose where measurement accuracy matters. For those, use a certified Type 1 or Type 2 sound-level meter. The Calibration sheet improves the relative accuracy of readings on your device but does not turn the app into a certified instrument.