Can adding sound make a plane quieter?
tap the headphoneA plane engine drones outside Nia's ear. Her headphone has a tiny microphone and a tiny speaker. The speaker may add one more sound. Could adding sound make the roar smaller?
Pressure can rise above or dip below
+ means above the resting air pressure. − means below it. Neither is good or bad.
Two signed pressure values make one total
pressure snapshot+3 + +1 = +4
same signopposite signs
Same-sign values grow. Opposite-sign values leave a smaller leftover.
Scan the engine's repeating pattern
moment in the dronemoment 1 · pressure +3
first momentlater moment
The mic records this amber pattern. The speaker's plan is still blank.
The microphone heard the whole wiggle
The speaker may answer at every instant. Its pressure will add to the engine beside Nia's ear. What should it play?
Use the one-instant rule across the whole new pattern.
Which speaker plan leaves the smallest total wave at Nia's ear?
Change the speaker plan. Watch all three rows.
speaker plansame-shape copy
same shapeequal opposite
size of the total2.00 × engine
