HowLoudDo Cheap Decibel Meters Work?
Yes, for most purposes. A typical low-cost handheld meter reads within about ±2 dB of a reference instrument at everyday levels, which beats a phone and is plenty for comparing appliances, checking a workshop or supporting a noise diary. What you do not get is certification: legal disputes and workplace compliance require a Class 2 or Class 1 meter with a calibration certificate.
What the classes mean
| Type | Tolerance (IEC 61672-1) | Typical use |
|---|---|---|
| Uncertified budget meter | ±1.5 to ±3 dB claimed, not verified | Home, hobby, DIY, first look at a noise problem |
| Class 2 | ±1.5 dB at 1 kHz, wider tolerances at frequency extremes | Environmental and occupational surveys, council enforcement, most legal use |
| Class 1 | ±1.1 dB at 1 kHz, tight across 10 Hz–20 kHz | Laboratory work, product certification, expert witness |
A phone with a good app sits roughly at ±3–5 dB; see using your phone as a decibel meter.
Where budget meters cut corners
- Microphone quality. Electret capsules drift with humidity and age; readings can wander by a few dB over a year.
- Frequency response. Cheap meters are reasonably flat from 100 Hz to 8 kHz and unreliable outside that, which matters for bass complaints and dBC readings.
- Time weighting and peak. Many only offer Fast and Slow, no true peak hold, no Leq averaging. Without Leq you cannot produce the number regulations ask for.
- Calibration. A "calibrated at the factory" sticker is not a certificate. Class meters are checked against a 94 dB / 114 dB acoustic calibrator before and after each survey.
- Range. 30–130 dB is common; the floor may be higher than stated, so a quiet bedroom reads 35 rather than 28.
When a cheap meter is enough
Choosing the quieter of two fans. Checking that a workshop or gym stays under 85 dB. Setting a limit for a rehearsal room. Verifying that a car exhaust or a generator is roughly where the spec says. Documenting neighbour noise for a diary before the council brings its own instrument. In all of these a 2 dB error changes nothing.
When it is not
Court cases, planning conditions, workplace exposure records, product noise labels and anything where a number will be challenged. Here you need a Class 2 meter at minimum, a calibrator, and a certificate less than a year or two old. Renting one for a week is often cheaper than buying.
A quick sanity test for any meter
Put the meter and a second device side by side on a steady broadband source, such as a fan or running tap, at the same distance. If they agree within 3 dB you are in good shape; if not, use the calibration adjustment on the online meter or app to match the better instrument. A handheld calibrator (94 dB at 1 kHz) settles the question properly and costs less than most meters.
Frequently asked questions
How accurate is a cheap decibel meter?
Typically within ±2 dB of a reference at mid frequencies and normal levels, less accurate for bass, very quiet rooms and impulsive peaks.
Is a phone as good as a cheap meter?
Close, on a good phone with an app that disables audio processing. A dedicated meter is more consistent, has a better microphone and offers Leq and peak functions.
What is a sound level calibrator?
A small device that fits over the microphone and produces an exact 94 dB (or 114 dB) tone at 1 kHz. You adjust the meter to read that value before measuring.