It is the sound of the station.

More so than the distant rumble and roar of the trains, than the jostling and jockeying of the taxi line, than even the daily din of hurried travelers echoing through the grand hall of 30th Street Station.

Even in the quiet hours it is there, signifying comings and goings: Clickety-clack, clickety-clickety-clack.

For more than three decades, by far the most charming sound of 30th Street Station has been the ticker-tape whirl of the giant flip-board departures board, an anachronistic thing in a city slowly but steadily shedding its anachronistic trappings.

Now it will be no more.

Soon the clicks and clacks of the flip board will be notes excised from a city's clamorous symphony. Another disappeared sound. Another memory.

Amtrak will replace 30th Street's traditional flip-board display - one of the last of the old-timey boards along Amtrak's Northeast Corridor - with a digital display. One without, I'm sure, European charm and a Wheel of Fortune hum.

The board's time was just up, said Amtrak spokesman Mike Tolbert.

Known as a Solari board for its Italian manufacturer, the board has become obsolete, he said. Parts are hard to find. And importantly, a digital board will better meet requirements of the Americans With Disabilities Act by making it easier to read.

There is no timetable for the change. There are talks about retiring the board to the Railroad Museum of Pennsylvania in Lancaster County, though a sound cannot be retired. It just goes away.

"It was the sound of the station," said Pattie Kearn, the 30th Street Station manager.

Yes, Kearn said, the sign, like the old gal she was, had grown stubborn and forgetful in her advancing age, sometimes refusing to post certain trains or confusing numbers with letters. There was that scary episode two years ago, when suddenly, during rush hour, one side of the sign went blank and stayed that way for months.

Now, sadly, said Kearn, the station will have to find a new sound.

Perhaps because the earliest denizens of our fair city set their timepieces to the tolling of a very famous bell, Philadelphians have long been concerned with marking the passing of sounds as they fade.

In his book, The Philadelphia Almanac and Citizens' Manual, Ken Finkel, an American studies professor at Temple, wrote of one early Philadelphia sound archivist, the dedicated Miss Kate H. Rowland. So intent was she on preserving the cries of 19th- and early 20th-century Philly street vendors that she committed them to verse and song.

She sang a collection of them at a January 1920 meeting for the City History Society of Philadelphia, including this peculiar ditty of a Philly peach hawker: "Here are your peaches at your door, if you don't buy mine you get no more, for the wagon's not mine and the horse is blind."

Around the same time Rowland sang her songs, Christopher Morley, the legendary columnist for the Philadelphia Evening Public Ledger, documented the sounds of Philadelphia neighborhoods he encountered on his sojourns through the city.

In Kensington, the "deep violin note of the Columbia Avenue sawmills." In Fishtown, the rumble of the hucksters' wagon along the asphalt paving, "the occasional tinkle of a piano in some cool, darkened parlor."

There are sounds long gone. The thwack of wooden wheels across cobblestone, the screech of metal along departed trolley lines, the rumbling of trucks and the bartering and bickering of vendors at the long-shuttered Dock Street fruit markets, the clink of cocktail glasses and the swoosh of the gilded curtain at Palumbo's nightclub on Ninth Street.

And there are sounds of the city we may miss all on our own. For me, there's the sound from an old apartment window near I-95, the traffic passing in the night sounding like waves. And the sound of a beloved friend's laugh as he glided up to the rail of a bar where I worked as a bartender. The bar and the friend are gone. I can still hear his laugh.

Soon the sound of the flip board will disappear. The first time I heard it, I was in my 20s, shuffling between old, not-quite-finished lives in D.C. and New York, and a new, not-quite-started life in Philadelphia. Stops all, along the Northeast Corridor.

To me, the whirl and clack of the board was the sound of the in-between. The sound of transition - the sound between departure and arrival. Of expectation, waiting. Of change. Eventually, it was the sound of home itself.

It is a lovely sound. I will miss it.