The 2021 white noise devices study, explained

The researchers varied volume and distance and measured with the NIOSH Sound Level Meter app. Details below come from the publisher’s abstract.

The NIOSH source on occupational limits explains that its 85 dBA reference belongs to workplace exposure, not general environmental listening. Moving that number into a nursery recommendation changes the question it was designed to answer.

Our reading tip: whenever a paper says “below the threshold,” finish the sentence with “which threshold, for whom?” Then ask whether the study actually followed people and measured the outcome you care about. A product result and a child’s health outcome are different kinds of evidence.

We reviewed the publisher’s indexed abstract and available section excerpts, not the complete article or product tables. We cannot verify a ranking of individual models, reconstruct every test condition, or tell you how a current product version compares.

For a shopping decision, ask for measurements tied to the exact model, software version, sound, setting, and position. A percentage on one volume slider cannot serve as a documented comparison with another product. These are practical requirements for reproducibility, not new measurements by Lullasure.

The NIOSH app documentation reports laboratory accuracy within ±2 dBA and states that meeting its cited Type 2 instrument requirements requires a calibrated external microphone. That distinction belongs to NIOSH’s specified setup; it does not validate every phone, app, or homemade comparison.

When you save a reading, record how it was obtained. A bare decibel number leaves the next reader guessing about microphone location, settings, and background sound. Repeating a documented check can be more informative than comparing unrelated screenshots.

For infant sound machines, the AAP’s 2023 policy favors greater distance, the lowest volume, and limited use. A tested distance is not a blanket approval.

Our volume and placement guide explains the practical setup question. The white noise all-night guide keeps exposure duration visible as its own decision.