Stories tagged hearing

Jan
26
2012

What’s the quietest thing you can hear? A pin drop? The pitter-patter of a mouse? Applause for my clever title? Now imagine if you could hear bacteria moving or cells dividing!*

To hear these sounds, you won’t use your boring old ears. Instead, you’ll be able to hear them with your eyes! Well, actually, you won’t even be able to use your eyes. You’ll need to use a little math…these sounds are really small, folks.

Let’s take a step back for a second. Hearing is simply the detection of vibrations by tiny bones (and hairs) in your ear. Those vibrations are then sent through a sensory nerve (the cochlear nerve) to the brain’s cerebral cortex, where it is translated and interpreted. Easy, right? However, our ears can only detect sounds as quiet as 0 decibels (dB), which is near total silence. (For reference, a whisper is about 15 dB, normal speech is about 60 dB, and a jet engine is 120 dB) To me, “near total silence” is pretty good, but scientists have found a way to detect sound levels as low as -60 dB. This is about a million times more sensitive than the hearing threshold of the human ear! Nanoear Prototype #1: Scientists scrapped this version.  It just ended up pooping all over.
Nanoear Prototype #1: Scientists scrapped this version. It just ended up pooping all over.Courtesy DanCentury

Researchers at the Nanosystems Initiative Munich (NIM) used gold nanoparticles, laser beams, microscopes, and the Fourier Transformation (read: math) to create a nanoear]. The way it works is to suspend a single gold nanoparticle with a red laser beam (an optical trap), create a small sound, then watch the gold nanoparticle oscillate (using a microscope, of course). The scientists tested their newfangled nanoear in two steps: In their first trial, they used a needle as the sound source, and they were able to actually see the nanoparticle vibrate. In the second step, the researchers used heat as their sound source- I know, crazy! On the same surface as the red-laser-suspended nanoparticle, they fixed a small number of gold particles and heated them with a green laser. The very weak sound waves caused vibrations in the nanoparticle that were imperceptible to the eye, but when the scientists applied the Fourier Transformation, they were able to show that the nanoparticle was, in fact, oscillating, and thus confirming the high sensitivity of the nanoear. This method of "hearing" will allow us to learn about the teeny-tiny movements of cells and their organelles, for example, or any other microscopic object.

I can see a modern re-make of the classic tale A Christmas Carol, by Charles Dickens:
Fred: Let’s play similes!
Fred’s wife: Oh, I do so love this game!
Fred: Ok, let’s start with, quiet as…
Fred’s wife: Quiet as a bacterial flagellum!!
Fred: Right!
[Party guests buzz with excited agreement. Fred’s wife nailed it.]

*Cells dividing must surely make the same sound as blowing bubbles into water with a straw. They probably won’t even have to test that.

It's the feel-good movie of the year.

Kinda puts a new spin on this poll question.

You can learn more about cochlear implants here.

You can see similar movies from your home computer by searching You Tube.

Nov
04
2009

Blue, blue, my ears are blue.: The blue morpho butterfly hears through ears on its wings.
Blue, blue, my ears are blue.: The blue morpho butterfly hears through ears on its wings.Courtesy William Warby

The blue morpho does. Scientists have found that this large butterfly of Central and South America has ears on its wings. These primitive ears can distinguish between the high-frequency sound of a bid singing, and the low-frequency sound of a bird flapping its wings. A singing bird is a sitting bird, and thus no threat to the morpho, but a flying bird could be attacking, and detecting those sounds tells the butterfly when to beat a slow, erratic retreat.

(Wait a minute…Blue Morpho…wasn’t he a character in Yellow Submarine Reloaded?)

...and, let's face it, who doesn't? You, too, can master the art of echolocation.

Jun
24
2009

This is another good strategy: Decoy ears.
This is another good strategy: Decoy ears.Courtesy niclindh
Just kidding, of course. Whisper into either ear, and you’ll probably get all sorts of nothing. I’m cold like that.

For most people, though, it turns out that speaking into someone’s right ear is a good way to get what you want. Not a perfect way to get what you want, but it seems to help.

Apparently it’s been widely accepted that the right ear is usually dominant in “listening to verbal stimuli” (I suppose that means that you pay more attention with that ear, or that that ear pays more attention itself, as it were), but a new study has explored how this plays out in actual human behavior. It was tested in the most sophisticated of human laboratories: the European discotheque. By asking for cigarettes.

I imagine that there has never been a scientific study with “What?!” shouted so many times. Nonetheless, the researchers, sweating and bedecked in glowsticks, determined observed several things over the course of three studies. In the first two, they found that when clubbers couldn’t hear a cigarette request very well, they offered their right ears most often, and 72% of cigarette negotiation took place on the right side. In the third study, the researchers approached people intentionally from either the right or the left when asking for cigarettes, and those clubbers who were asked through the right ear yielded “significantly more” cigarettes.

The reason for this, the scientists think, is that the right ear is (oddly) more directly connected to the left hemisphere of the brain, and the left brain is dominant when it comes to words and numbers. (The left brain is sort of like your inner math nerd, and the right brain is sort of like your inner art nerd. Your inner jock is the stem.) This direct connection, I suppose, makes people more naturally inclined to listen to verbal requests through the right ear, and makes requests received through the right ear more easily processed than those taken through the left ear.

Because I don’t like doing what I’m told, no matter what I’m told, I am now wearing a right ear patch at all times. It has a skull and crossbones on it, to give me a sort of nautical, pirate-getting-dressed-while-drunk look. Please contact me if you’d like to order your own ear patch. Unless you’d rather go around giving everybody cigarettes all the time.

Oct
09
2008

Pipe down: What's causing all this noise we're hearing down here under the water?
Pipe down: What's causing all this noise we're hearing down here under the water?Courtesy Whit Welles
“Hey, quiet down up there. We can’t hear a thing down here.”

No, it’s not the lament of some landlord who’s rented out the upper level apartment to a rock-and-roll loving tenant. It’s a case being heard by the U.S. Supreme Court right now pitting whales off the coast of California against the U.S. Navy.

Justices heard oral arguments yesterday on the case. Environmentalists are challenging the Navy’s claim to perform training exercises along the California coast which use extensive and strong sonar transmissions. The sound waves of those sonar blasts can harm whales and other marine mammals, petitioners contend, with sounds that can be up to 2,000 times louder than a jet engine. Some scientists feel that sounds that loud can cause whales to lose hearing loss, bleed on the brain and possibly lead to mass strandings on beaches.

Decision spot: The U.S. Supreme Court is the site of a pending decision pitting U.S. Navy sonar training exercises against the health of marine mammals like whales.
Decision spot: The U.S. Supreme Court is the site of a pending decision pitting U.S. Navy sonar training exercises against the health of marine mammals like whales.Courtesy Thor Carlson
The Navy says that strong sonar level is critical to be able to detect submarines that can elude weaker modes of sonar.

Based on justices’ questions and reactions, however, it appears that court is leaning toward siding with the Navy and national security concerns.

Here’s a full report on yesterday’s court session. Justices were pretty upfront in stating their lack of expertise in mammal biology and national defense matters.

So if you had to decide on this conflict, where would you come down on this question? Does the health and a comfort of whales trump national security? Is loud sonar just an unfortunate byproduct of keeping our national interests safe? Share your thoughts here with other Buzz readers.

Feb
14
2005

Researchers at the University of Michigan have restored the hearing of deaf guinea pigs.

Hair cells in the cochlea of each ear convert sound waves into nerve signals. The cells are easily damaged by loud noises, aging, infections, and certain medications. And, once damaged, hair cells don't grow back. But the researchers used a virus to insert a gene into ear cells that made new cochlear hair cells grow.

During fetal development, the gene makes some cells in the ear into hair cells. In other ear cells, called supporting cells, the gene is inactive. But researchers were able to use the gene to convert existing supporting cells into hair cells.

First, they deafened the guinea pigs by destroying their hair cells with antibiotics. Four days later, they used a virus to insert the corrective gene and get new hair cells to grow. The researchers observed increases in the guinea pigs' brain activity when they exposed them to noises—proof that the new cells are working.

Now researchers are studying whether or not the animals can tell the difference between loud or soft noises, or noises of different frequencies. They're also studying animals deafened in other ways, older animals, and animals deaf for longer periods of time before treatment starts. It will probably be a decade or so before the technique can be tried on human patients.