Hotels face a noisy problem: sleep comes at a premium.

Noise is the top guest complaint after cleanliness, and fixing it is difficult and costly due to sources ranging from external street activity to thin walls and elevator noise. Hotels are increasingly investing in soundproofing and “sleep” amenities, but design costs and reservation systems that don’t let guests pick quiet rooms hinder progress. Travelers can improve odds by requesting high floors, rooms away from elevators, or quiet sections, and some hotels market sleep-focused amenities, though many guests still rely on earplugs or white-noise machines to sleep.