A New "Metamaterial Silencer" Creates Passive Noise Canceling, Without Blocking Airflow

How do you block sound without cutting off airflow? It's a tricky question, but new work out of Boston University shows a promising advance.The tricky part comes from the fact that we call "sound" is actually a series of vibrations, a long chain reaction of air molecules knocking together to pass along an acoustic signal, creating a constantly changing pattern of high- and low-pressure air for our ears to register. That's why the most straightforward method to silence sounds, like a noisy piece ...