Why did people in different parts of India hear air sirens in last few days. People in parts of Rajasthan, Bihar, and Mumbai heard air sirens on September 30, October 6, and October 8-9, respectively, as part of a nationwide exercise. States purchased air sirens without any specifications after Operation Sindoor, and the government wants to address these gaps by developing an advanced warning system. The sirens were sounded to help with this project.