(CNN) — Noise can affect sleep for better or worse. White noise machines that emit just that — consistent noise — fall squarely in the “better” category. Constant white noise, like the kind produced by a white noise machine, has been shown to improve sleep quality because it helps mask sudden bursts of noise that may help some people more easily fall and stay asleep.

“White noise machine” is a blanket term that consists of basic machines that do the bare minimum (that is, emit white noise at varying volumes) to high-end pieces of tech that feature lights, automations and more. We tested eight top-rated machines, aiming for devices with a variety of sound options and great volume control for heavy and light sleepers alike. After two months, two stood above the rest: