Four Apps Out of 192
Phone sound meter apps are free, instant and widely trusted. They have been tested properly, and the results are specific.
When acoustic measurement is part of a wider workplace review, cognitive offloading can add operational context, but it should not be treated as a substitute for calibrated sound data.
The study
NIOSH evaluated 192 sound measurement applications across iOS and Android.
Ten iOS apps met the selection criteria for functionality, features and calibration capability.
For an independent reference on this subject, see Cirrus Research sound-level meter guide.
Four met the accuracy criterion — a mean difference within ±2 dB(A) of a reference type 1 sound level meter.
A follow-up study in 2016 found that those same four, used with external calibrated microphones, measured within ±1 dB. (JASA — peer-reviewed.)
What this means in practice
A randomly chosen app is unlikely to be accurate, and it will give you a confident number regardless.
The error is not random noise around the right answer. It comes from the microphone, its automatic gain control, the phone's audio processing and the absence of calibration, and it can run in one direction consistently.
An app reading 78 dBA where the real level is 85 does not tell you it is uncertain. It tells you you are below the limit, which is the failure that matters.
The Android problem
NIOSH states that verifying the accuracy of an Android-based app is not currently possible.
iOS devices share a common hardware and software architecture, so an app verified on one behaves predictably on others. The Android ecosystem is fragmented, and microphone hardware differs enough between devices that a single verification does not transfer.
This is a statement about verification rather than about quality — an Android app may be accurate on a particular handset, and there is no way to establish it.
What NIOSH built
A free Sound Level Meter app for iOS, developed with one of the four apps' developers and tested to the same criteria.
With a calibrated external microphone it meets type 2 requirements of the relevant standard and measured within ±1 dB of the reference over 65–95 dB SPL in laboratory conditions.
NIOSH states plainly that it is not a replacement for a professional meter or a dosimeter and is not for compliance purposes, which is the kind of limit statement worth noticing in a product page.
It is named here — the only product named on this site — because it is free, it comes from the agency that did the testing, and the testing is published.
What a phone can and cannot do
Can: tell you roughly where you are — quiet room, busy office, hazardous workshop. Enough to decide whether to measure properly.
Cannot: produce a number for a compliance record, capture a full-shift dose, or be trusted to within a few decibels without calibration.
Which is a genuinely useful capability as long as the second list is known.
The short version
- NIOSH tested 192 sound meter apps; 10 met selection criteria and 4 met the accuracy criterion of ±2 dB(A)
- With external calibrated microphones those four reached ±1 dB, published in JASA
- App error is not random around the right answer — it can run consistently in one direction and reads as confident
- Android accuracy cannot currently be verified because the hardware ecosystem is fragmented
- The NIOSH app is free, iOS only, tested to the same criteria, and stated by NIOSH not to be for compliance use
- A phone can tell you roughly where you are, which is enough to decide whether to measure properly