TITLE: Another Way Our Students Are Different From Us AUTHOR: Eugene Wallingford DATE: December 18, 2006 4:00 PM DESC: ----- BODY: On my CS 1 final exam, I asked the students to suggest a way that we could hide a string in a sound, where a Sound object is encoded as an array of sound samples in the range [-32768..32767]. Here is the last part of the question:
Under your scheme, how many characters could you hide in a song that is 3:05 long?My caricature of the typical answer is...
It depends.Actually, most of the students were a bit more specific:
It depends on the sampling rate.Of course it does. I was looking for an answer of this sort:
(185 * sampling rate) / 100... for a scheme that stored one character every 100 sound samples. It never occurred to me that most students would get as far as "It depends on the sampling rate." and just stop. When they realized that they couldn't write down as answer such as "42", they must have figured they were done thinking about the problem. I've been doing computer science so long, and enjoying math for much longer, that I naturally wanted to write a formula to express the result. I guess I assumed the students would want to do the same! This is yet another example of how our students are different from us. Fortunately, nearly all of them came up with a scheme for hiding a text that would work. Some of their schemes would degrade the sound we hear considerably, but that wasn't the point of the question. My goal was to see whether they could think about our representations at that level. In this, they succeeded well enough. Well, I guess that depends. -----