To direct the Comptroller General of the United States to issue a report on the effectiveness of local outdoor siren systems, and for other purposes.

HR 9959 directs the Government Accountability Office (GAO) to study how well local outdoor siren systems alert people during weather emergencies. The study will review systems across states, counties, and municipalities, examining infrastructure condition, costs to replace systems, how sirens interact with other alerts (like FEMA's system), and cybersecurity. It will evaluate whether current activation standards and system upgrades could improve effectiveness. The GAO must submit a report to relevant congressional committees within 18 months of the bill becoming law, helping local governments develop better emergency response policies. This bill directly affects local emergency management agencies and communities relying on these sirens.