Application guide
How to Measure Bedroom Noise at Night
A quiet bedroom is the hardest thing a phone microphone is ever asked to measure, and it is the reading most meters get wrong in the same direction: too high, with total confidence.
The near silence flag is in the free version.The core problem
Why a silent room so often reads 55 dB
The microphone has a floor
An iPhone microphone produces a small amount of noise of its own, at a level near minus 55 dBFS. Below that point the microphone is measuring its own electronics rather than your room, and no amount of arithmetic recovers a real number from it.
A meter that adds its calibration offset to that self noise and prints the result produces a plausible looking 50 to 60 dB in a room where you can hear a clock. That figure is not a measurement of anything.
What the app does instead
dB Decibel maps the microphone floor through your calibration offset, adds a 3 dB margin, and reports near silence for anything at or below that. It refuses the reading rather than inventing it.
For a bedroom this is the useful answer. "Quieter than this phone can resolve" means the room is not your problem, and you can stop measuring and start looking at what wakes you instead.
The number to look at
L90 is the background, L10 is the disturbance
An average across a night is close to meaningless. Eight hours of 32 dB with four passing motorbikes averages out to something that describes neither the quiet nor the motorbikes. Two percentile figures do the job properly, and both are in the free version.
- L90
- The level exceeded 90 percent of the time. This is the floor your room actually sits at: the fridge, the ventilation, the street at three in the morning. If L90 is high, the room itself is the problem and no amount of dealing with events will fix it.
- L10
- The level exceeded 10 percent of the time. This is the loud tail: the events that pull you out of sleep. A large gap between L90 and L10 means a quiet room with intrusions, which is a completely different repair job from a uniformly noisy one.
- Leq
- The energy equivalent level for the whole night. Useful for comparing one night against another, not for describing a single one.
Overnight
Recording a whole night
Sleep Soundscape, part of the Pro unlock, logs a level reading once a second through the night and gives you a morning summary: the quietest hour, the loudest hour and a count of disturbances. That turns "I keep waking up" into "it is hour three and hour six, every night, and hour five is fine", which is something you can act on.
Practically:
- Put the phone at head height near the pillow, not on the floor and not on the windowsill. Measure where your ears are.
- Plug it in. A night of continuous metering with the screen alive is not a light load on a battery.
- Out of the case, microphone edge clear of the bedding.
- Record several nights before concluding anything. One night tells you about one night.
- Keep the position identical between nights, exactly as you would for a neighbor log.
The honest part
Where a phone runs out at the quiet end
Two limits are worth knowing about before you trust a night of data. The first is the floor described above: below it there is no reading, only a flag. The second is frequency. Phone microphones lose sensitivity at low frequencies, with roll off reported below roughly 100 Hz, and low frequency energy is exactly what travels through a building. Bass through a party wall, a heat pump outside, traffic rumble through a floor: all of these feel worse than they measure on a phone.
So if the app reports a low level for something that is unmistakably keeping you awake, believe yourself, not the number, and write down what you heard alongside what was measured. A certified meter with a proper capsule is the tool that settles low frequency arguments.
What this app is not. Readings are approximate (±dB) and come from an uncalibrated phone microphone. dB Decibel is an environmental sound measurement tool. It is not a certified sound level meter, not a dosimeter, not hearing protection and not a medical device, and it is not suitable for occupational, regulatory or legal compliance. That wording is taken from the disclaimers inside the app itself.
Get the app
Find out what your bedroom really sits at
Live dB(A), Leq, L10 and L90, and the near silence flag are in the free version, which is enough to answer the question for most rooms in one evening. The overnight timeline with the morning summary is part of the one time Pro unlock.
Free to download. iPhone, iOS 18 or newer. Optional one time Pro unlock, no subscription.Keep reading