Noise Level Index (ambient sound reaching worker)

Sound level is the noise level measurement at a given point in time.

Time Weighted Average (TWA) is sound level averaged over an eight-hour period.

The Noise Level Index includes both immediate sound level measurement (SLM) and the TWA.

We aim to convert this to a 1-10 scale based on much noise reaches a worker.

A smartphone app is the simplest and least expensive way to track this.

You can download the free NIOSH SLM app on iOS devices.

Sound Meter is an app for Android devices.