In India's bustling megacities, honking is a common form of communication among drivers. But in this case, one person's language is another person's noise pollution.

Noise from roads, airports and equipment like leaf blowers has been linked with serious health impacts. Decades ago, the U.S. government passed a law limiting it, but it has no teeth.

Operators must begin installing new directional speaker systems or use in-ear listening devices.

More than 100 trolley tour buses would undergo equipment modifications to limit noise spillover.

A drop in shipping traffic is reducing underwater noise, so scientists are listening for how whales and other marine life are responding.