What did the high-pitch sound at Ford's procession mean?

Yep. Boatswain’s whistle salute.

At the World War II memorial, lights bathed the granite arch commemorating the Pacific theater as Ford’s nighttime funeral procession stopped there in tribute to his years as an ensign and gunnery officer.

The other arch, representing the Atlantic theater, stood in darkness.

Ford served as a navigator and gunnery officer on the aircraft carrier USS Monterey.

As the hearse stopped, Navy Chief Boatswain’s Mate Carlos Ribbot, 41, stepped forward, saluted with his right hand and with his left raised a Boatswain’s pipe hanging from an ornately braided rope lanyard around his neck.

Clad in white shirt, black tie, and black tunic with gold hash marks and white eagle on his left sleeve, Ribbot, a native of Humacao, Puerto Rico, then played the three long, solemn notes that constitute “piping the side,” the Navy’s traditional farewell.

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PIPING THE SIDE

The proper name of the shrill metal whistle, used by the navy is the boatswain’s call, and sounding it is known as piping. The term “Piping the Side” originated in the days of sailing ships, from the way visiting captains arrived on board. Instead of climbing the ladders, they were hoisted aboard by a group of sailors called the Side Party, a title shortened in time to “the side.” The order to “pipe the side” was given by the officer of the watch, and the boatswain relayed this to the men using his call.

This salute to a visiting dignitary now consists of the call being blown twice, once as the dignitary’s boat draws alongside the ship’s accommodation ladder, and again as that person mounts the ladder and steps inboard. The procedure is reversed as the dignitary departs. Traditionally, the side is also piped when a corpse is brought on board, taken ashore, or committed to the deep.

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http://www.rcl554.webcentre.ca/commem/Piping.html