Long term exposure to constant droning sounds could cause issues in language centers of the brain.
When we rely on sounds for kids, we stick to sounds that mimic the more random/non-droning sounds you encounter in nature. Birds chirping in a forest, evening crickets and frogs etc.
They may be citing a study that circulated recently about how white noise is the reason why we have an autism epidemic. I can't seem to find the study, though. But I do remember laughing.
Anecdotal but I used a noise machine that played brown noise because I was informed it mimics the sound of the baby’s womb. My daughter is extremely advanced in all areas of learning now at 5 years old. Her first word was hi at 4 months.
When we rely on sounds for kids, we stick to sounds that mimic the more random/non-droning sounds you encounter in nature. Birds chirping in a forest, evening crickets and frogs etc.