The decibel is a logarithmic scale, which is a mathematically elegant way of saying it does not behave the way you expect. Adding 10 dB is roughly a doubling of perceived loudness. Adding 3 dB is a doubling of actual sound energy — clearly audible, but nothing like twice as loud.
The practical consequence is that the gap between a comfortable room and a genuinely damaging one is smaller than it sounds. Between an office at 60 dB and a nightclub at 100 there are only forty points, and the second one is doing about ten thousand times the acoustic energy of the first.
What the numbers feel like
Where a phone speaker sits
A phone at maximum volume produces somewhere around 90 to 100 dB measured close to the speaker. At arm’s length on a table that is a loud phone and nothing more — sound drops off quickly with distance, roughly 6 dB every time you double it. Held against your ear it is a different proposition entirely, and that is the entire reason both platforms ship hearing-safety caps.
Which is worth knowing before you run a cleaning cycle, because those run at full volume deliberately: the amplitude is what moves the water. Put the phone down, or hold it away from you, and take earbuds out first. At arm’s length it is fine. At your ear for thirty seconds it is unpleasant and unnecessary.
How a phone measures sound
The microphone converts pressure into a signal, and the app converts that signal into a level. There is no exotic hardware involved, which is both why every phone can do it and why the result needs reading with some care.
- It is uncalibrated. A professional meter is calibrated against a reference tone; a phone is not. Expect to be within a few decibels of the truth, not within one.
- The microphone has limits at both ends. Below roughly 30 dB it hits its own noise floor, and above about 100 to 110 dB it clips. Readings outside that band are not meaningful.
- Covering the microphone ruins it. A hand, a case, a table surface — the microphone is a small hole on the bottom edge and anything over it reads low.
- Sound falls off with distance. A reading is a reading *at that spot*. Measure where your ears actually are, not where it is convenient to hold the phone.
- Automatic gain control fights you. Phones are built to make voices sound even, which is the opposite of what a meter wants. Good implementations disable it; it is a real source of drift in bad ones.
Things worth measuring
- Your commute. Underground trains routinely run above 90 dB and nobody thinks of it as loud exposure because it is normal.
- The gym. Many run classes at 95 to 100 dB for an hour, which is well past the point where the clock is running.
- Your bedroom at night. Sleep quality is measurably affected above about 35 dB, and most people have never checked.
- A restaurant before you sit down. If a meter says 80, you will be shouting through dinner.
- Your own speaker. Useful for settling the question of whether a phone is genuinely quiet or the room is genuinely loud — which changes what you do about it. The volume guide covers the rest.
- A concert. So you know whether the earplugs in your pocket are optional.
Hearing damage does not announce itself
Noise-induced hearing loss is cumulative, permanent and painless. The hair cells in the cochlea do not regenerate, and the loss starts in the high frequencies — which is why the first sign is usually not “things are quieter” but “I cannot follow a conversation in a noisy room”. By then it has been happening for years.
Ringing after a loud event is the clearest warning there is. It means the exposure was enough to produce a temporary threshold shift, and repeated temporary shifts become a permanent one.
The protective habits are unglamorous and effective: distance, since 6 dB comes free with every doubling; time, since halving the exposure buys the same as 3 dB; and earplugs at concerts and in loud workplaces, which cost almost nothing and are the single highest-return thing on this list.