Whisniper(Whisper + Sniper) is a device for one to transmit pre-recorded message to someone faraway without disturbing others around.
City of Seoul recently started transforming the city to encourage non-motor vehicle types of transportation. The city's initiative to build better environment for walkability ranges from refurbishing old sidewalks to repurposing elevated roadway to walkway, like High Line of NYC.
It is all good, with big funds and administrative power to build walkable infrastructure, yet one major drawbacks for walk on streets of Seoul I think, is the loud music(noise) from the shops to attract(or distract) pedestrians.
Here, I suggest a fictional world where all the sounds and messages are carried like a concealed weapon and only directed to whom are in need, like sniper of sound, not like an assault rifle of current state.