Super-Sound Detector Picks Up Silence, Makes It Roar
CAMBRIDGE, Mass., Jan. 15., 1934 — The fact that a suit of clothes creaks with every movement of the body is revealed by a super-sound detector at the Harvard university physics laboratory.
When this supersonic listener is turned on in a room perfectly quiet to the ear, the air is filled with noises. They are supersounds, air waves vibrating at 20,000 or more a second, too high to be audible to the human ear.
The noises arise apparently from every kind of motion, however slight. Among these supersounds the creaking of a good suit of clothes is among the noisiest. Stand in front of the mechanical listener and slowly bend one elbow. “Grrump,” goes the racket of the flaxlug fabric and keeps up this sound as long as the arm is in motion. Light a match, and above the soft flare which is audible to the ear the supersonic instrument picks up another noise resembling the distant rumble of a street car. Rubbing the palms of the hands together emits a stream of these sounds. Tearing a piece of paper sounds like far-off machine gun fire.
A roomful of men trying to remain entirely quiet registers on the supersonic device like the noises of a herd of elephants. This detector, designed by Dr. G. W. Pierce, Rumford professor of physics, is part of an extensive investigation of supersounds. In the air these inaudible waves travel farther than ordinary sounds. They also are transmitted by the other substances which carry sound, suggesting possible normal uses for signalling. In water they can be heard nearly 10 miles.
Music can be transmitted over a specially arranged supersound beam. For this Dr. Pierce uses the inaudible sound of a Gallon whistle, which sends out vibrations at the rate of about 25,000 a second. When the listening device is turned to the whistle it makes a high, clear note. But when a phonograph record is connected electrically with the whistle, the clear note modulates to carry faithfully every variation in sound of a full orchestra. These modulations are all in supersound frequencies, so that the music cannot be heard except when the listening device is cut in to receive the whistle and reduce its high frequencies to the audible range.
—The Bee, Danville, VA, 1934

Super-Sound Detector Picks Up Silence, Makes It Roar

CAMBRIDGE, Mass., Jan. 15., 1934 — The fact that a suit of clothes creaks with every movement of the body is revealed by a super-sound detector at the Harvard university physics laboratory.

When this supersonic listener is turned on in a room perfectly quiet to the ear, the air is filled with noises. They are supersounds, air waves vibrating at 20,000 or more a second, too high to be audible to the human ear.

The noises arise apparently from every kind of motion, however slight. Among these supersounds the creaking of a good suit of clothes is among the noisiest. Stand in front of the mechanical listener and slowly bend one elbow. “Grrump,” goes the racket of the flaxlug fabric and keeps up this sound as long as the arm is in motion. Light a match, and above the soft flare which is audible to the ear the supersonic instrument picks up another noise resembling the distant rumble of a street car. Rubbing the palms of the hands together emits a stream of these sounds. Tearing a piece of paper sounds like far-off machine gun fire.

A roomful of men trying to remain entirely quiet registers on the supersonic device like the noises of a herd of elephants. This detector, designed by Dr. G. W. Pierce, Rumford professor of physics, is part of an extensive investigation of supersounds. In the air these inaudible waves travel farther than ordinary sounds. They also are transmitted by the other substances which carry sound, suggesting possible normal uses for signalling. In water they can be heard nearly 10 miles.

Music can be transmitted over a specially arranged supersound beam. For this Dr. Pierce uses the inaudible sound of a Gallon whistle, which sends out vibrations at the rate of about 25,000 a second. When the listening device is turned to the whistle it makes a high, clear note. But when a phonograph record is connected electrically with the whistle, the clear note modulates to carry faithfully every variation in sound of a full orchestra. These modulations are all in supersound frequencies, so that the music cannot be heard except when the listening device is cut in to receive the whistle and reduce its high frequencies to the audible range.

The Bee, Danville, VA, 1934

Show us your pearly whites! This engineered “shrinking gel” prompts tooth tissue formation.
(Images courtesy of Basma Hashmi, Harvard SEAS.)

Show us your pearly whites! This engineered “shrinking gel” prompts tooth tissue formation.

(Images courtesy of Basma Hashmi, Harvard SEAS.)

Capasso teaches a genre of science at Harvard University so spectacularly complex that it might as well be magic as far as the lay person is concerned.
Forbes

Harvard physicists have proposed a device to capture energy from Earth’s infrared emissions to outer space—a possible new source of renewable energy. Their analysis of the thermodynamics, practical concerns, and technological requirements will be published this week in PNAS.

“The key is in these beautiful circuit diagrams,” says Prof. Federico Capasso. “We found they had been considered before for another application… and been completely buried in the literature and forgotten. But to try to explain them qualitatively took a lot of effort.”

LEARN MORE

(Images courtesy of Eliza Grinnell; Steven J. Byrnes; and Federico Capasso and PNAS.)

When you meet someone who is doing something interesting, ask if they have time to get coffee, and then ask them who else they know who you could get coffee with. You should be drinking a lot of coffee when you’re job searching.
Eleanor Fort, Explore Careers in Energy & Environment panelist, Associate for State and Federal Climate and Energy Policy Program, CERES. Read the full story.  (via ocsharvard)

A sneak peek inside Harvard’s machine shop!  Students learn welding, precision milling, 3D printing and more—all part of a hands-on engineering education. Learn more.

A sneak peak inside Harvard’s machine shop!  Students learn welding, precision milling, 3D printing and more—all part of a hands-on engineering education. Learn more.

If the Oscars were perfectly predictable with math, the suspense would be gone and the ceremony wouldn’t be exciting anymore. But the Academy of Motion Picture Arts and Sciences is just that – a combination of art and science.

Harvard undergraduate Ben Zauzmer ‘15 (applied math), who correctly predicted 81% of Oscar winners last year using data and mathematics.

With the Academy Awards coming up this weekend, check out the front-runners—according to Ben’s statistical model.

A new DOE project led by researchers at Harvard SEAS and Lawrence Berkeley National Laboratory will study human impacts on tropical rainforest and climate.
Based in Brazil, the field campaign will enable scientists to study the intricacies of the natural state of the Amazon rainforest atmosphere and land systems, and how these may be perturbed by human influences such as pollution and deforestation. Learn more.

A new DOE project led by researchers at Harvard SEAS and Lawrence Berkeley National Laboratory will study human impacts on tropical rainforest and climate.

Based in Brazil, the field campaign will enable scientists to study the intricacies of the natural state of the Amazon rainforest atmosphere and land systems, and how these may be perturbed by human influences such as pollution and deforestation. Learn more.

Harvard engineers have created an artificial muscle that recreates the twisting motion of heart muscle.