That's what we learned from neuroscientist Dr. Seth Horowitz of Brown University; true silence is non-existent. "In truly quiet areas," he writes in his book, The Universal Sense, "you can even hear the sound of air molecules vibrating inside your ear canals or the fluid in your ears themselves."

No wonder we can't sleep on some nights. Here's what we learned from him:

Humans are good at choosing what they hear.

We often ignore the sounds around us at a conscious level. (Think New Yorkers.)

Anywhere there is energy, including intergalactic space, there is sound because it is a vibratory region. Even black holes make sounds.

Humans and animals can respond to changes in sound that occur in less than a millionth of a second.

The presence of sound drives the evolution, development, and day-to-day function of the mind.

There is a massive "vertical gun" at the NASA Research Center, and sound scientists use it to blow up stuff to see what's inside it all, and make note of the sounds the stuff makes.

One scientist blew a hole in the moon to see what happened.

What is an ear? An organ that senses the changes in pressure of molecules. That's what hearing is.

Sharks have relatively high auditory thresholds, meaning the sound has to be pretty loud for them to respond to it.

Modern snapping shrimp create deafening underwater choruses by snapping their claws.

Spiny lobsters sound like they're playing the violin underwater.

Human technology and innovation are now letting us hear things we've never heard before, including the sound of thunder on Venus and the winds on Saturn's moon, Titan.

Changing the place you listen from can radically affect what you hear.

Hearing, Tinnitus and Sound Sensitivity: Dr. Natan Bauman

A frequent guest on our show through the years, Dr. Natan Bauman is an expert in helping those plagued by tinnitus, a persistent ringing in the ears. His techniques involve re-training the brain to focus on other, more important events in your life.

In addition, Dr. Bauman directs a clinic for those who are ultra-sensitive to certain sounds, including the directional signal in the ear, television commercials, even fabric rubbing against fabric; and he treats those who find all sounds too loud. (Even normal conversation is received as extremely loud to them.)

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GUESTS:

MUSIC:

“Gne Gne,” Motefiori Cocktail

“Central Nervous Piston,” El Ten Eleven

“Sorry About Your Irony,” El Ten Eleven

“My Only Swerving,” El Ten Eleven

Lori Mack and Jonathan McNicol contributed to this show.