For years the nattering has been quarantined in other corners of the transportation system — elevated subways and plodding buses, Amtrak and commuter rail cars without the word “quiet” on them.

But more than a century after the founding of New York City’s underground subway, technological progress has layered a new din over the relative tranquillity of traveling preachers, fussy children and mariachi bands with loose change in their hats.

New Yorkers on cellphones.

On Thursday, Gov. Andrew M. Cuomo announced that 30 more underground stations would have cellphone service, bringing the total to 36, all in Manhattan. At some of the city’s busiest hubs, including Times Square and Rockefeller Center, riders will be able to make and receive calls, send text messages, and access Wi-Fi. Mr. Cuomo said the change would also bolster security, allowing travelers to call 911 in an emergency.

Another consequence of the improvements, though, was discussed little: With many of the newly connected stations bunched closely together, officials said that riders might be able to find cellphone signals not just on platforms but on moving trains themselves.