What is sound (and why it can topple buildings)

How it forms, how we hear it, and what it can do.

Why Stradivarius violins sound so good. Hint: It’s the f-shape

In the 18th century, violin craftsmanship reached its peak in what came to be known as the Cremonese period — he golden age of violinmaking. During this age, Italian families like Amati, Stradivari, and Guarneri were on high request to deliver the finest violins, meant to be played in the finest concert halls of Europe. Whether the old masters employed a scientific method to their manufacturing process to churn out the best possible sound is still debatable, but what’s certain is that string instruments have gone a long away in terms of acoustic efficiency since the middle ages when the lute or oud dominated courthouses. So, what gives these top-notch violins, like Stradivarius, their signature, powerful sound? According to a team of MIT engineers and violinmakers at the North Bennet Street School in Boston they key to a violin’s sound is the shape and length of its “f-holes,” the f-shaped openings through which air escapes.

Thin metasurface absorbs sound near perfectly, while producing electricity at the same time

Researchers at the Hong Kong University of Science and Technology have created a thin metamaterial surface that is capable of absorbing nearly all of the acoustic energy (sound).  Unlike conventional sound absorbing material that is sometimes only effective when meters thick, the metasurface is deeply “subwavelength” and therefore much thinner. There’s a catch though: the system has been demonstrated for near perfect sound absorption