What constitutes a "homework" question?

I lurk in several groups.
I've observed cases of lazy students.

I've also observed cases of qualified persons in one field being 
mistaken for students of another field when asking questions outside of 
their specialty.

What triggered this post was the hesitant reply of this group to a 
question posed by canmc.

He seemed to state EXPLICITLY a question that I've been meandering about 
for some time.

If the voicebox is seen as a squarish wave source and mouth/tongue/nasal 
passages as a filter with 5 or 6 resonant frequencies. [ apologies to 
English majors ;]

canmc's question makes perfect sense.

Depending on your (theory/point of view) there are either 5 or 6 
characteristic frequencies of speech.

I'm not sure of how strongly the "speech recognition" community has been 
influenced by "we've always done it this way". My "GUT" feel is that 
there is an unrecognized component of "we can't recognize frequencies >x".

As I see it, there are 5/6 significant frequencies.
There are 1/2/? typically interfering bands.

Why would one not ask for a filter which emphasizes 5/6 bands of 
interest while negating 1/2/? interfering bands?

I hope this makes sense to someone ;)

In article <10m8mmki9t3qub4@corp.supernews.com>,
Richard Owlett  <rowlett@atlascomm.net> wrote:
>I lurk in several groups.
>I've observed cases of lazy students.
>
>I've also observed cases of qualified persons in one field being 
>mistaken for students of another field when asking questions outside of 
>their specialty.

Yes, it just happened to me in fact, in a reply from Rune to one of
my articles.  I'm not insulted, though -- I'm relatively new here,
I've been participating on and off in this group, and Rune likely
hadn't noticed me before.

Several participants here are also educators themselves, so they
recognize the folly of spoon-feeding answers to students who just
want to make a grade.

That said, I think it's a difficult skill to recognize a cleverly
disguised homework question posted by a student.  I think it's
especially difficult in this newsgroup, for there are other
participants (like me) who aren't in school, and for whom practical
knowledge, or even canned solutions such as those found in the
"Numerical Recipes" books, would be a great help to our own fields
of employment or research.

I wish someone would publish a "DSP Recipes" book.  Not necessarily
with computer code, but with algorithms or formulas.  I made a start
with a derivation of digital coefficients for all-pole filters,
which I published at http://unicorn.us.com/alex/allpolefilters.html
-- I wish I had a reference like that when I started out on my
search for generalized formulas for the filter coefficients.

>Depending on your (theory/point of view) there are either 5 or 6 
>characteristic frequencies of speech.
>
>I'm not sure of how strongly the "speech recognition" community has been 
>influenced by "we've always done it this way". My "GUT" feel is that 
>there is an unrecognized component of "we can't recognize frequencies >x".
>
>As I see it, there are 5/6 significant frequencies.
>There are 1/2/? typically interfering bands.
>
>Why would one not ask for a filter which emphasizes 5/6 bands of 
>interest while negating 1/2/? interfering bands?

Seems to make sense to me.  As I understand it, one would need a ratio
of polynomials resulting in gain in some bands, and rejecting other
bands.  Might one achieve that by cascading several simpler filters,
bandpasses and bandrejects?

-Alex

Richard Owlett wrote:
> I lurk in several groups.
> I've observed cases of lazy students.
> 
> I've also observed cases of qualified persons in one field being 
> mistaken for students of another field when asking questions outside of 
> their specialty.
> 
snip
> 

I think there's something about the DSP field that tends to result in 
questions being framed like they came from homework or an exam.  When I 
can I answer these the same way I did when I was working as a TA: I give 
background information so the guy can answer the question, but I don't 
just give the answer.  This works for me as a way to respond, because 
when I'm asking questions I want an answer that goes into the "why" of 
the question rather than just giving the answer at hand (i.e. don't tell 
me "1/2", tell me to look up the Nyquist limit on the web).

-- 

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Richard Owlett wrote:
>[snip]

> Why would one not ask for a filter which emphasizes 5/6 bands of 
> interest while negating 1/2/? interfering bands?
> 
> I hope this makes sense to someone ;)
> 

Neither axlq nor Wescott addressed this ;)

Richard Owlett wrote:

> Richard Owlett wrote:
> 
>> [snip]
> 
> 
>> Why would one not ask for a filter which emphasizes 5/6 bands of 
>> interest while negating 1/2/? interfering bands?
>>
>> I hope this makes sense to someone ;)
>>
> 
> Neither axlq nor Wescott addressed this ;)

I don't know about axlq, but I didn't address it because it's out of my 
area of expertise.  Ask me about automatically generating tuning 
parameters for PID controllers, or the best anti-alias filter to use in 
motion control.  _Then_ I'll answer.

-- 

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

axlq@spamcop.net (axlq) wrote in message news:<ck1ndu$b6t$2@blue.rahul.net>...
> In article <10m8mmki9t3qub4@corp.supernews.com>,
> Richard Owlett  <rowlett@atlascomm.net> wrote:
> >I lurk in several groups.
> >I've observed cases of lazy students.
> >
> >I've also observed cases of qualified persons in one field being 
> >mistaken for students of another field when asking questions outside of 
> >their specialty.
> 
> Yes, it just happened to me in fact, in a reply from Rune to one of
> my articles.  I'm not insulted, though -- I'm relatively new here,
> I've been participating on and off in this group, and Rune likely
> hadn't noticed me before.

I'm sorry if I misjudged the background for your question. I can, of 
course, not speak for others, but posting traditions don't usually have 
any influence on how I answer people here. We have all (even Jerry, 
believe it or not!) been newbies at one point or another. I can recall 
at least a handfull of threads during the last month or so, that were 
started by obvious newbies, which escalated into very detailed 
discussions that involved quite a few of the experienced regulars here.

Whether you post your first or your 10,000th post, it's the question, 
not the person, that decides if and how I choose to answer. Your question 
was a bit too close to "homework" for me not to mention my suspicion. 
On the other hand, it was a damned good question, and I found it 
worth spending time on. You had obviously spent some effort trying to 
solve it before asking here, which was why I answered.

> Several participants here are also educators themselves, so they
> recognize the folly of spoon-feeding answers to students who just
> want to make a grade.

Well, yes. I have done a bit of teaching and have supervised a few MSc 
students, and my reaction to students follows a pretty consitent pattern. 
I usually get an impression (at least when I speak to people face-to-face)
whether they are really interested and make the effort themselves, or 
if they  are merely "easy riders". Which tends to have an effect on 
how I follow them up.

> That said, I think it's a difficult skill to recognize a cleverly
> disguised homework question posted by a student. 

The matter (at least for me) is not so much whether the questions are 
homework, as whether people make an effort. Within reason, of course.

> I think it's
> especially difficult in this newsgroup, for there are other
> participants (like me) who aren't in school, and for whom practical
> knowledge, or even canned solutions such as those found in the
> "Numerical Recipes" books, would be a great help to our own fields
> of employment or research.

That's the charm of DSP. You can push it as far you like in any given 
direction. HW vs SW, theory vs application, education vs industry...

> I wish someone would publish a "DSP Recipes" book.  Not necessarily
> with computer code, but with algorithms or formulas.  I made a start
> with a derivation of digital coefficients for all-pole filters,
> which I published at http://unicorn.us.com/alex/allpolefilters.html
> -- I wish I had a reference like that when I started out on my
> search for generalized formulas for the filter coefficients.

I think the best book available right now, is Rick Lyons' "Understanding 
DSP". It actually contains the closest thing to a "DSP Recipes" chapter
I have ever seen. 
 
Rune

Rune Allnor wrote:

   ...

> I think the best book available right now, is Rick Lyons' "Understanding 
> DSP". It actually contains the closest thing to a "DSP Recipes" chapter
> I have ever seen. 

I strongly endorse that recommendation. Steven W. Smith's book, "The
Scientist and Engineer's Guide to Digital Signal Processing" is a nice
companion for certain topics. It's on line at http://dspguide.com/. I
found it worthwhile to buy a copy. Are you familiar with
http://dspguru.com/ ? there's a lot of good stuff there. Harmony Central
has already been mentioned. There are several on-line and downloadable
filter-design programs you can find with Google.

Jerry
-- 
When a discovery is new, people say, "It isn't true."
When it becomes demonstrably true, they say, "It isn't useful."
Later, when its utility is evident, they say, "So what?  It's old."
                                     a paraphrase of William James
���������������������������������������������������������������������

Jerry Avins wrote:

> When a discovery is new, people say, "It isn't true."
> When it becomes demonstrably true, they say, "It isn't useful."
> Later, when its utility is evident, they say, "So what?  It's old."
>                                      a paraphrase of William James

Jerry, how does the original run?
I can't find a quote like it on the web.


Martin

-- 
Quidquid latine dictum sit, altum viditur.

Martin Eisenberg wrote:

> Jerry Avins wrote:
> 
> 
>>When a discovery is new, people say, "It isn't true."
>>When it becomes demonstrably true, they say, "It isn't useful."
>>Later, when its utility is evident, they say, "So what?  It's old."
>>                                     a paraphrase of William James
> 
> 
> Jerry, how does the original run?
> I can't find a quote like it on the web.
> 
> 
> Martin

I read it years ago and reconstructed it later. I don't remember which
work it was in. If I had the reference, it might not be a paraphrase.

But some things, like a few of my sigs, take on a life or their own. To
wit: http://www.lcs.poli.usp.br/~acarezia/frases.html.

Jerry
-- 
Never wrestle with a pig. You'll both get dirty, but the pig likes it.
����������������������������������������������������������������������

In article <f56893ae.0410062149.783e072f@posting.google.com>,
Rune Allnor <allnor@tele.ntnu.no> wrote:
>I think the best book available right now, is Rick Lyons' "Understanding 
>DSP". It actually contains the closest thing to a "DSP Recipes" chapter
>I have ever seen. 

Thanks!  Also to Jerry for seconding the recommendation.

-Alex