Sound counts vary by model: compact travel units often offer about 11 sounds, many classic bedside machines list around 20 non-looping sounds, and some models advertise up to 26 selectable sounds.
They use a mix of power sources: AC/electric or USB power, built-in rechargeable batteries, or replaceable batteries. A few models list both battery and electric power options.
Most provide precise volume control and sleep timers (commonly 30/60/90 minutes). Some include memory functions that restore prior settings, and a few offer additional auto-shutoff or configurable sleep-timer options.
Common travel features include compact dimensions and a small footprint, USB power or USB charging, built-in rechargeable batteries on some units, occasional international power adapters, and secure fasteners or designs suited for on-the-go use.
Most machines list ABS or generic plastic for the housing; some models include EVA or fabric accents in their construction.
Commonly advertised features include noise masking and precise volume control to help drown out disruptive sounds, multiple non-looping sound options, and capabilities promoted to support speech privacy.
