who to trust Cecil or a physics teacher...

ok well my family has been arguing about whether or not a ducks quack echos. bro #1 says that according to cecil and snopes a quack echos. bro #2 says that according to a physics teacher at his school, it is a known fact that a ducks quack (along with certain other animals) doesnt echo. HMMM…

Can a physics teacher BE a quack?

Most sounds echo, so the default assumption would be that so do ducks’ quacks. Therefore, in order to assert that this was untrue, someone would have to give either a physical reason for it happening, or a certain experiment which found it to happen. Can this physics teacher produce either of these? If not, go with Cecil.

An echo is a result of pressure waves in the air reflecting off a surface and being returned back toward the source.

It is remotely conceivable that some peculiarity of a particular surface texture would be such that a ducks quack, with its unique (to certain particular ducks that is) frequency spectrum, would be dispersed rather than reflected.

But that possibility is so remote that it isn’t really worth considering. Furthermore, even if such a surface did exist there would most probably be only one of them in the whole world. In addition it would probably only be dispersive for a small set of ducks’ quacks. I’m only trying to point out that the probability that as a general fact, the claim about a duck’s quack not echoing is nonsense.

Given a reflective surface, sound waves are reflected even if they come straight from Donald Duck himself.

PS - Tell bro #2 not to argue with his physics teacher until after he gets the final grade that the teacher is ever going to have an opportunity to give him.

I breathlessly await a complete disproof of my analysis so that I can learn one more new thing.

I can’t see why a duck’s quacks don’t echo.

A duck quack happens to be fairly similar to a burst of noise. If you add noise and noise together, you just get more noise. It’s much more difficult for your brain to seperate the sounds, so to your ear it sounds like one big long noise. Hence, you don’t hear much of an echo. Something like a drum beat, or some idiot yelling “echo” at the top of his lungs, has many more auditory cues that allow your brain to pick out the original sound and the echo.

Sound is just a pressure wave through air. Ask your physics teacher to explain why pressure waves of a particular frequency content won’t bounce off of a solid object. I for one want to hear what he has to say. :smiley:

No really. Cecil is right. I’ve tried it with the local ducks, and they don’t echo. There isn’t really any reason that they shouldn’t. I mean, sure, they’re strange creatures, but stcill echo. One thing I learned from school : don’t trust what your teachers tell you. Frequently, they try to get away with murder.

The fact is, there is no reason that a duck’s quack shouldn’t echo just like any other sound.

Do not argue with a teacher, it isn’t worth it. Best bet is for bro#2 to ask his teacher why a duck’s quack doesn’t echo. Ask for a reason based in the science of Physics, not some glurge sent through an email. Bro#2 can be fairly insistent in this request because he “just wants to understand how it all works.”

I would be very amused to hear the teachers answer.

Also, try using spacers of some kind to put some gaps between the DVD unit and the units above and below it, so that the air can flow nicley all the way round. My stereo amp was acting up because the cd player on top of it was cutting off its air.

Either bro #2 or the physics teacher is talking out of their behind.

We’ve done this one before.

Cecil speaks.

And here’s snopes take on it.

I also remember reading a page someplace where someone had actually really gone out to prove or disprove this statement. Introduced a duck to a very echoy location. It echoed.

Perhaps you remember that from Cecil speaks.

Oh yeah. Perhaps I should re-read my links properly before citing them. :smiley:

This place needs an embarrassed grin smiley.

I would point out, also, that you are not necessarily disagreeing with the physics teacher, only with the brother’s interpretation of what the teacher said. If I had a nickel for every time a student has misinterpreted something I said, I’d have… a whole stack of nickels.

I vote that you DO argue with your physics teacher about it. But don’t just say, “The guys at the Straight Dope say you’re wrong!”.

Use the opportunity to educate yourself. Learn why sounds echo. Then go to your teacher and say, "You know, you got me thinking about that duck thing. But echoes are just pressure waves bouncing off of hard objects, right? As a physicist, can you tell me what is special about a Duck’s quack that makes it impossible to echo?

If he argues with you, set up an experiment - get a duck call, and go to the gymnasium and blow it and measure the echo. Write it up, and take it to your physics teacher. Make him support his statement. Politely ask him to treat the issue scientifically and not as a subject of hearsay.
A lot of good will come out of this. For one thing, you’ll learn a lot more about physics than you do just sitting in a class and absorbing what a talking head is saying. Second, it’ll hopefully make your teacher think twice about spouting nonsense to children under his tutelage.

I wish more kids took an active interest in their own education, rather than just sitting in class writing down whatever the guy with an education degree at the front is saying.

A duck call is not a quaking duck. Record a duck quaking and then play that in a gymnasium and measure the echo.

A recording of a quacking duck is not a quacking duck. Bring a quacking duck to the gymnasium. :smiley:

I agree bring a quacking duck, a quaking duck may be too unstable. :smiley:

Hell, just tell him that it’s a Quacking Duck Sim 1.0.

But seriously - I think kids SHOULD question their teachers when they believe the teacher is wrong. It’s a good skill to learn to be skeptical, and it keeps teachers on their toes and maybe in the future teaches them to keep their mouths shut unless they know what they are talking about. The last people in the world who should be spouting old wives’ tales and myths as fact are teachers.

I got kicked out of a class in grade 12 once when I disputed a teacher’s facts and she refused to debate the issue with me. She claimed that the United States didn’t actually declare war against Japan (she was in the middle of a rant about how evil the U.S. was, and used the ‘dropping an A-bomb on innocent people’ angle). When I said, “well, there was this little thing called WWII…”, she said “Yes, but this was Japan, not Germany. The U.S. wasn’t at war with Japan.”

This was a modern history class, BTW. The lesson I learned from that is that just because someone is a teacher doesn’t mean they have a clue what they are talking about.

The problem with contradicting a teacher is that a teacher may decide to injure your academic career as a result. Not fair and difficult to prove. A lot of places, especially schools designed to shovel mindless drones into college for the final mindless drone programing for the real world, place grades above actual education. Students in those areas are in the uncomfortable possition of having to play for grades at the cost of learning. Some classes are good for getting into college and for learning something. Those who really want to learn do it outside of class. On the other hand if you have loud enough parents the teacher can be cowed by way of the administration so challenge away.

I personally count myself lucky at having a very loud and aggressive Italian-American mother. Especially when one of my teachers decided it was appropriate to dock me points on an assignment because of my honest feedback on the assignment evaluation a week after the assignment was handed in and grades (but not the work itself) were handed back.

I can attest to the fact that duck quacks do echo. I have heard them in an open air mall, the ducks where in the fountain.