Can your iPhone measure decibels accurately?
Yes, within limits. NIOSH researchers found that the best iOS sound meter apps read within about ±2 dB of professional reference meters in lab tests — good enough for awareness and exposure screening. Phone microphones still struggle with very loud peaks and are not a legal substitute for a calibrated SPL meter.
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What the research actually says
The most-cited evidence comes from NIOSH researchers Chucri Kardous and Peter Shaw, who tested smartphone sound measurement apps against calibrated laboratory reference systems. Their findings: a handful of well-built iOS apps measured within roughly ±2 dB(A) of the reference — comparable to the tolerance of a Type 2 field meter — and accuracy improved to about ±1 dB when an external calibrated microphone was used. That research is the reason the free NIOSH Sound Level Meter app exists at all: iPhones have consistent enough audio hardware that a carefully calibrated app can do real screening work.
Why iPhones do better than Android here
Apple ships a small number of hardware models with tightly controlled microphone components, so an app can ship per-model calibration profiles. Android spans thousands of devices with wildly different microphones, which is why the NIOSH app shipped on iOS only.
Where phones still fall short
Phone microphones are built for voice. They roll off very low frequencies, and at high levels — sustained sound above roughly 100 dB — they can compress or clip, under-reading the true level. Wind, cases, and where you hold the phone all add error. For anything legal, occupational, or contractual, you need a calibrated meter that meets IEC 61672 — see how phone apps compare to dedicated SPL meters.
Try it now
You can estimate your current noise level with the free online decibel meter right in your browser, or get calibrated readings, history, and exposure alerts with Decibel Shield for iOS.