Learning through sound
The audible world contains vast amounts of information about the world around us. Scholars from across Stanford are exploring this invisible landscape as a research tool and as a way of understanding each other.
Academics is often a visual pursuit – reading journal articles, examining manuscripts, looking through a microscope. But some things can only be learned through sound. The boom of volcanoes, buzz of mosquito wings or tone of a person’s voice all convey information lost to a visual observer. The challenge in all of these is learning how to make sense of the sounds around us, in some cases with technology and in others by simply listening to one another more carefully.
Beyond helping us interact with the world and with each other, sound can be an almost physical tool. Frequencies beyond the range of human hearing can wake up sleeping appliances and arrange heart cells in the lab. Sound waves can even be a means of peering into the body and diagnosing health conditions.
Stanford scholars from across medicine, engineering, social sciences and the arts are working together to interpret and manipulate this audible world, and to restore hearing to those whose ability is diminished. They’re even helping people learn to listen more carefully to each other. Here, we highlight examples of researchers harnessing sound to understand the Earth.
Listening to climate change
Chris Chafe, director of the Center for Computer Research in Music and Acoustics, composed the piece of music based on the global average temperature and CO2 from A.D. 850 to 2016 – data compiled by his colleagues at the University of California, Berkeley.
As temperatures rise and CO2 levels increase, the music goes from a low hum to an increasingly frenetic whine. What people might not see day to day becomes hard to ignore through sound.
Techniques for making fast-flying aircraft quieter could pay off with higher power output from wind farms.
Sound waves generated by burbling lakes of lava atop some volcanoes could provide advance warning to people who live near active volcanoes.
It’s a sound that can keep even the weariest from falling asleep: the high-pitched whine of a mosquito. This irritating buzz already makes people run, slap and slather on repellent. But if bioengineer Manu Prakash has his way, it may also prompt people to take out their cellphones and do a little science.
A new cellphone app called Abuzz not only identifies the species but puts it on a map. The resulting distribution can help scientists track mosquitoes that carry diseases like malaria, yellow fever, dengue, West Nile virus, chikungunya and Zika.
Invisible sound waves carry a physical force. They rattle against inner ear cells to create the sensation of sound, and similar waves can trigger devices to turn on, detect hidden tumors or even probe the seafloor. These waves hold power well beyond what we can hear.
Understanding through listening
It’s one thing to hear and another to listen. The act of listening and communicating can help ease troubled relationships, steer medical decisions and even bring the past to life. But it’s not always easy, which is why some researchers are trying to unravel how we listen and why it’s so important.
In 2009, Mount Redoubt, a volcano outside Anchorage, Alaska, began spewing towering ash plumes more than 12 miles tall. Before it did so, a sequence of tiny earthquakes emanated from the volcano’s innards. Though inaudible to listeners on the surface, sensitive seismic instruments placed along the active volcano’s slopes picked up the vibrations.
Sped up 60 times their original speed, the recording’s pop, pop, popping accelerated into what Alaskan seismologists working with Stanford geophysicist Eric Dunham nicknamed “the scream.” Then, a brief silence before “Boom!” An explosion.