directed sound
n. Sound waves aimed and focused so they can only be heard by a person or persons within a specific area.
In a potentially revolutionary development, at least two separate and very different companies have already turned the concept of directed sound into reality.

Speakers work basically by physically creating waves in the air, using a membrane or other mechanism to pump the vibrations out, which means they disperse in an ever-wider arc. In contrast, Holosonic Research Labs Inc. and American Technology Corp. disrupt the air with ultrasonic waves at about 100,000 hertz, a frequency not even dogs can hear.

This enables the companies to transmit a highly focused sound somewhat like how a flashlight beams a focused light. A person can speak in a normal voice and be heard privately up to 600 yards away — yet anyone more than a couple of feet to either side of the intended listener won't hear a thing.
—Chris Marlowe, “Sound technology — for your ears only,” The Hollywood Reporter, July 23, 2003
Imagine standing in the frozen-food aisle of your supermarket, staring at a tub of your favorite double-fudge brownie ice cream. Suddenly, a voice comes out of nowhere to tell you there's a two-for-one sale on that very treat. But only you hear the message. In fact, the guy studying the cookie-dough choices 2 feet away is listening to a different ad — which you can't hear. …

[S]o-called directed sound may soon be accosting consumers in all kinds of real-life settings. A small San Diego company, American Technology Corp. (ATC), has already begun shipping a product called the HyperSonic Sound system [HSS], which uses inaudible ultrasonic waves to create vibrant sound out of thin air.
—Arlene Weintraub, “Here you hear it, there you don't,” Business Week, February 17, 2003
1987 (earliest)
Implanting computer chips into the brains of chimpanzees and using the animals as expendable pilot crews, genetically re-engineering future pilots to be a "better" pilot, … developing tiny robots to be used for sabotage — such are problems with which the U.S. airforce research is dealing.

It became known to the newspaper "Mercury News" that the above-mentioned "promising ideas" alongside hundreds of others were discussed at an air force "brainstorming" conference held at Dayton, Ohio, in 1985. …

[O]ne of the proposals that was highly assessed by airforce representatives and recognised as deserving to be developed envisages creating generators of long-range directed sound beams which could cause panic among enemy forces.
—Vladislav Orlov, “Militaristic projects of American futurists,” TASS, February 10, 1987
When the inventors of directed sound (which is also called point-focused sound, focused sound, and sound beams) talk up their product, they usually trot out various innocent-sounding scenarios. For example, Mom and Dad listen to their music in the front of the minivan while the kids listen to their music in the back, without disturbing each other's listening pleasure. Similarly, a husband watches late-night TV in bed while his sleeping wife hears nothing.

However, when pressed for further examples these inventors don't take long to get around to the marketing possibilities, which generally include standing in front of a product at the supermarket and immediately hearing an ad for that product. See example citation #2 for more on this new marketing low that's both creepy and alarmingly Minority Reportish.