How Loud Is a Circular Saw? What NIOSH Measured

The NIOSH Power Tools Database was built so that tool purchasers could buy quiet. It reports A-weighted sound power level for individual tool models, together with hand-arm vibration values and technical specifications such as blade diameter, rated power and rated speed.

The tools were tested in accordance with ANSI S12.15 and ISO 3744 for sound, and ISO 5349 for vibration. Crucially, the dataset gives both a loaded and an unloaded figure, because most electrically powered hand tools are specified under ANSI S12.15 in the unloaded condition — which is not how anyone uses a saw.

For circular saws the loaded figures in the published excerpt run from about 103 dBA to about 113 dBA. Unloaded figures for the same tools are usually several decibels lower, though not always: a few models measured higher unloaded, which is a useful reminder that the relationship is not a fixed offset.

Sound power describes how much acoustic energy a source emits in total. It is determined in a controlled acoustic environment and it does not change when you step back. Sound pressure is what a microphone or an ear responds to at a given point, and it depends on distance, room surfaces and where the source is placed.

This is why a 108 dBA sound power figure must not be read as 108 dBA at your ear. It is also why comparing a tool's sound power against an occupational exposure criterion — which is defined in sound pressure — is invalid without a measurement at the operator position.

NIOSH itself keeps the two apart. Its hearing-protection guidance in the same document is stated in terms of sound pressure level above 85 dBA, not in terms of the sound power values in the table.

Blade choice matters more than motor size for the sound you hear. Tooth count, kerf and plate stiffness change both the cutting noise and the ringing of the blade itself, and a dull blade forces the motor to work in a way that alters both level and character.

The workpiece is a source in its own right. A large sheet of plywood on sawhorses behaves like a radiating panel; the same cut on a supported, damped board sounds different. Cutting metal, as one dataset entry does, produces a different spectrum again.

The room adds the rest. In a hard-surfaced garage, reflections raise the level at your ear well above the same cut made outdoors, without the tool emitting one decibel more energy.

In the EU, building-site circular saw benches appear in Directive 2000/14/EC under equipment subject to noise marking only. That means a guaranteed sound power level must be declared and marked on the machine, but no permissible limit value applies to it — unlike compressors or lawnmowers, which carry limits.

That difference is worth understanding when you compare machines. A marked figure tells you what the manufacturer guarantees; a limit value tells you what the law caps. Only some machines have both.

Handheld circular saws for general use are not in that annex at all, which is one reason the NIOSH dataset is the more informative source for them.

A phone cannot verify a sound power figure — that requires a reverberation room or a measurement surface of microphones around the source. What it can do is compare: this blade against that blade, this cut supported against unsupported, indoors against outdoors.

Uncalibrated, our meter reports an A-weighted digital signal level in dBFS rather than sound pressure, and high-level transients are exactly where consumer microphones and browser gain control interfere most. After a one-time local calibration it reports an estimated dBA figure, still on consumer hardware.

For anything that has to hold up — an occupational assessment, a hearing conservation programme — the measurement has to come from a calibrated meter or dosimeter at the operator position.