Like Bats, People 'Hear' Silent Objects

[Brian Roebuck]

Like Bats, People 'Hear' Silent Objects
Jennifer Viegas, Discovery News

The Sound of Silence

June 11, 2008 -- The song "The Sound of Silence" might hold more truth than ever imagined, suggests a new study that determined people can hear silent objects based on reflected and ambient sound.
Since blind individuals may be particularly tuned in to such sounds, the research helps explain how they can often find doorways, windows and objects without seeing or touching them. It may also lead to a better understanding of echolocation, the technique used by certain animals, like bats and dolphins, to detect reflected sound.

dsc.discovery.com/news/2008/06/11/hearing-sound.html

A useful skill for lost cavers?

[Azurerana]

Anybody else here walk around their home in complete darkness? It's pretty easy after a while.

Apparently there was one local cave owner who knew his cave well enough that he would walk through it without lights, and scare the bejesus out of loud, noisy cavers who were visiting by just suddenly appearing out of the dark.

We don't think about this kinesthetic sense very often, but again, everyone knows a local can go 65 on a windy mountain road that challenges the visitor to do 45 or 50. Why? Because you can tell where you are on the road by the way you lean in the car, and the noise the engine makes on the hills. How about canoeing or horseback riding, where you have to shift your weight to 'ride' more effectively?

We do an awful lot of things instinctually, then some scientist studies it and is amazed.
We measure distances by dropping rocks and listening for a splash. Most of this stuff we learned as kids, and later forgot.

Hellllooooooooooooooo......

[NZcaver]

Jun 20, 2008 22:01:31 GMT -5 Azurerana said:

Anybody else here walk around their home in complete darkness? It's pretty easy after a while.

Apparently there was one local cave owner who knew his cave well enough that he would walk through it without lights, and scare the bejesus out of loud, noisy cavers who were visiting by just suddenly appearing out of the dark.

We don't think about this kinesthetic sense very often, but again, everyone knows a local can go 65 on a windy mountain road that challenges the visitor to do 45 or 50. Why? Because you can tell where you are on the road by the way you lean in the car, and the noise the engine makes on the hills. How about canoeing or horseback riding, where you have to shift your weight to 'ride' more effectively?

We do an awful lot of things instinctually, then some scientist studies it and is amazed.
We measure distances by dropping rocks and listening for a splash. Most of this stuff we learned as kids, and later forgot.

Comfortably wandering around the house in complete darkness relying on sound is one thing, but I wouldn't want to try that in a cave. Maybe if I knew a cave really well, and it had a fairly even floor, no vertical drops, no water, no loose rock, etc. But still I think I'd rely more on feeling my way around (or a good LED headlamp!) in addition to listening for those little sounds.

This is a little off-topic from people "hearing" silent objects, but trusting your instincts (and doing it wisely) might be more appropriately compared with a race car driver on a closed course rather than a local on a mountain road. It does not impress me to see foolish people driving excessive speeds on mountain roads, around blind corners, over very rough surfaces, through quiet residential streets, etc just because they're local and they "know the road." Or for any other reason. I'm talking about totally inappropriate speed for the conditions, regardless of legal speed limits. Driving like that one *might* be able to anticipate the road, but can't possibly anticipate the actions of everybody else in their cars, on their bikes, or on foot.

I remember a TV ad campaign years ago about rural driving and the dangers of high speed, fatigue, and/or alcohol. It tried to emphasize that car accidents don't just apply to city folk. The catch phrase for the ads wasn't very inventive or at all subtle, but it got to the point. "Country people die on country roads."

[Azurerana]

Jun 22, 2008 15:10:51 GMT -5 NZcaver said:

I remember a TV ad campaign years ago about rural driving and the dangers of high speed, fatigue, and/or alcohol. It tried to emphasize that car accidents don't just apply to city folk. The catch phrase for the ads wasn't very inventive or at all subtle, but it got to the point. "Country people die on country roads."

Catchy phrase, but not really the truth around here, NZ. Alcohol, slick conditions, teens and prom night aside, most of the people who misgauge the curves and make the news are not locals. My comment had nothing to do with being against safe driving...it has a lot to do with orienting one's self in space and time. Non-drivers in my college carpool used to sleep on the way, and play a game to guess where they were before they opened their eyes if they woke up. I was correct about 80% of the time-- better than average.

Since I have depth perception problems, I'm always looking for hedges to help me figure out the 3D space around me. Sound is one of them. On the other hand, moms, baby sitters and spouses often use echolocation to find out where their charges or spouses are, and I couldn't possibly run machinery without the soundscape. I learned both from my mom. Soundscapes are interesting once a person pays attention to them, That's one thing I find disconcerting about the increasing reliance of people on MP3 players and other forms of constant background din.. Your attention is directed at an imaginary space between your ears, instead of to the world around you.

[NZcaver]

Jun 22, 2008 18:39:08 GMT -5 Azurerana said:

Catchy phrase, but not really the truth around here, NZ.

Well, you must have some good drivers down that way then. Maybe your intuitive locals are the exception rather than the rule.

Soundscapes are interesting once a person pays attention to them, That's one thing I find disconcerting about the increasing reliance of people on MP3 players and other forms of constant background din.. Your attention is directed at an imaginary space between your ears, instead of to the world around you.

You'll get no argument from me about avoiding the distraction of a constant background dim. But I think people like us are in the minority these days.

However I'm not quite seeing what you mean about parents, babysitters and spouses using echolocation to find their changes. Do you mean they make a sound and listen for it to bounce off the other person? I can't imagine that would work very well. You could just rely on the other person to make noise in reply - but that isn't really echolocation, is it?

[Rick Brinkman]

You know....I always thought it was ridiculous to think that bats only use echolocation to find their way. What about the feel of air currents, different scents, temp changes, humidity changes, and that bit of visible light as one gets closer to the entrance?

And as far as hunting for bugs....I think the flutter of wings would be MUCH louder to a bat than a tiny echo.

[Azurerana]

nzcaver said:

However I'm not quite seeing what you mean about parents, babysitters and spouses using echolocation to find their charges. Do you mean they make a sound and listen for it to bounce off the other person? I can't imagine that would work very well. You could just rely on the other person to make noise in reply - but that isn't really echolocation, is it?

Well, it is a wee bit of a joke, of course *|:-).
But seriously --maybe it is an Ozark thing...you yell, and see where the response comes from. Such as, "Anybody home?" You are, in fact, locating the other person by sound, not by seeing. It isn't that different than dropping a pebble down a well and listening for the splash, and then doing a rough calculation of the depth of the well.

You know, I probably could write up a proposal and get a a gagillion dollars to study human echolocation patterns in the Ozarks...sigh.... ;D

[bartell]

There is a sound to silence. In the recording industry, it's called "presence". Recordists record silence in a set or location. They also record the speech, dialog, music, or other subject. In the pre-digital days of film, the presence was mixed into the dialog, so that dubbed dialog sounded natural - not cleaner than the live sound. Nowadays, you can take the presence and subtract it from the subject audio, to remove noise.

Another technique uses something called an impulse. Say you want your home-recorded singing to sound like it was made in a cathedral. You take a mono mike to the cathedral, place it where you want the virtual voice to eminate from, and record a brief, sharp sound. This "impulse" might be a hand clap, for example. The impulse contains echo information.

Later, on the computer, you take the recorded singing, and convolve (multiply digits) it with the impulse data. Voila - it sounds exactly like you were singing in the cathedral.

And yes, I sometimes walk around the darkened house, counting steps and such, just for practice.