A team of researchers at the Honk Kong University of Science and Technology have developed a system that can eliminate nearly 99.7% of noise. Generally in acoustics study, a body would normally absorb sound when it has some of sonic insulation. So by combining these insulators into one body, you’ll continue to increase the capacity of the material to absorb sound. But how much of this can be built into one material at a given time. This would further create structural complications from a design point of view. You see most of these insulators absorb sound over small frequencies.
How did these researchers approach this?
Well the used resonators smartly. The word resonator is gotten from resonance. If you did basic physics in secondary or high school, this might ring a bell. The basic definition of resonance would be that feeling you get when a heavy duty vehicle passes by your house or office. You feel some sort of vibration. This is because the natural frequency of the ground you are standing on is the same as that of the vibrating vehicle. So these Honk Kong researchers put together a pair of the resonators (device or system that exhibits resonance) in one layer. They have been designed to resonate at the frequency of the body to which they are attached. Sound is produced at a certain frequency and so if sound waves incident on these resonators, they are designed to adapt the natural frequency of the body they are attached to thereby cancelling out noise/sound. When this happens, something known as Impedance is achieved.
Now remember that a pair of resonators were used. In a separate Engadget analysis, “the first resonator eliminates a majority of the incoming sound waves. However at very low energy levels (ie very quiet sounds), even the best resonator tends to scatter a little bit of the sound at its own frequency. That’s where the second resonator comes in — it’s tuned precisely to the first resonator’s frequency, allowing it create destructive interference for any sound the first resonator scatters.”
Together both resonators achieved a 99.7% result in absorbing sound.
I encourage you to read the full research using this link