Decrease Noise Levels Act This bill directs the Federal Aviation Administration (FAA) to revise its regulations to decrease the threshold for the day-night average sound level that constitutes significant noise from 65 decibels to 60 decibels, and adjust relative ranges of day-night average sound level accordingly. Additionally, the FAA must ensure that its community outreach related to aviation day-night average sound levels contains the results of its evaluation of alternative metrics to the current average day-night level standard, and create a publicly available report that outlines a strategy to reduce the maximum day-night average sound level in all residential areas to 55 decibels within 10 years.