On Thursday, March 30, 2017 at 12:17:44 PM UTC-4, robert bristow-johnson wrote:
> On Tuesday, March 28, 2017 at 10:49:13 PM UTC-4, cl...@claysturner.com wrote:
> >
> > In Krauss' book "Antennas", The Dolph Chebyshev solution is offered as a way to create a narrow beam from a broadside antenna array. Dolph presented his solution back in 1946.
> >
>
> amazingly, Clay, i have that book. took a course in antenna theory back in my undergrad days. we had a prof (Ronald Moe) who was hard-core EM. it's where i learned (with a trig substitution) that radiation patterns followed a polynomial (of cosine, i think) and we could design a great radiation pattern with Chebyshev polynomials.
>
> i think there are audio guys doing that with loudspeakers, but i cannot see how that can work for a wide bandwidth.
>
> r b-j
Very Cool you have his book! I actually have 3 of Krauss' books: Antennas, E&M, and Radio Astronomy. Even though he was a EE, he operated a radio telescope at OSU for years. He was most def. an E-Mag kind of a guy.
Clay
Reply by Greg Berchin●March 31, 20172017-03-31
On Thursday, March 30, 2017 at 11:17:44 AM UTC-5, robert bristow-johnson wrote:
>
> i think there are audio guys doing that with loudspeakers, but i cannot see how that can work for a wide bandwidth.
> On Tuesday, March 28, 2017 at 10:49:13 PM UTC-4,
> cl...@claysturner.com wrote:
>>
>> In Krauss' book "Antennas", The Dolph Chebyshev solution is offered
>> as a way to create a narrow beam from a broadside antenna array.
>> Dolph presented his solution back in 1946.
>>
>
> amazingly, Clay, i have that book. took a course in antenna theory
> back in my undergrad days. we had a prof (Ronald Moe) who was
> hard-core EM. it's where i learned (with a trig substitution) that
> radiation patterns followed a polynomial (of cosine, i think) and we
> could design a great radiation pattern with Chebyshev polynomials.
>
> i think there are audio guys doing that with loudspeakers, but i
> cannot see how that can work for a wide bandwidth.
>
I'd think you'd need our head in a vice to listen to them
or the phase effects might make you dizzy.
> r b-j
>
--
Les Cargill
Reply by robert bristow-johnson●March 30, 20172017-03-30
On Tuesday, March 28, 2017 at 10:49:13 PM UTC-4, cl...@claysturner.com wrot=
e:
>=20
> In Krauss' book "Antennas", The Dolph Chebyshev solution is offered as a =
way to create a narrow beam from a broadside antenna array. Dolph presented=
his solution back in 1946.
>=20
amazingly, Clay, i have that book. took a course in antenna theory back in=
my undergrad days. we had a prof (Ronald Moe) who was hard-core EM. it's=
where i learned (with a trig substitution) that radiation patterns followe=
d a polynomial (of cosine, i think) and we could design a great radiation p=
attern with Chebyshev polynomials.
i think there are audio guys doing that with loudspeakers, but i cannot see=
how that can work for a wide bandwidth.
r b-j
Reply by ●March 28, 20172017-03-28
On Wednesday, March 15, 2017 at 9:19:41 AM UTC-5, Eric wrote:
> Most software seems to focus on Hann, Hamming, and Blackman windowing.
> From the graphs I've seen, Dolph-Chebychev appears to outperform them:
> https://en.wikipedia.org/wiki/Window_function#Dolph.E2.80.93Chebyshev_window
>
> Anyone know why it isn't featured in DSP texts to the extent of the
> other windows above? Are there drawbacks?
In Krauss' book "Antennas", The Dolph Chebyshev solution is offered as a way to create a narrow beam from a broadside antenna array. Dolph presented his solution back in 1946.
Clay
Reply by robert bristow-johnson●March 24, 20172017-03-24
On Monday, March 20, 2017 at 10:40:10 AM UTC-4, Eric wrote:
> On Sun, 19 Mar 2017 09:37:06 -0700 (PDT), robert bristow-johnson
> <rbj@audioimagination.com> wrote:
>
> >but if you're trying to detect notes in the context of other notes playing, or if the note onset is *not* percussive (like say it's a horn or a human voice and they change from C to D in a legato manner), your problem is much, much harder.
> >
> >sorry for the bad news.
>
> Yeah, a percussive note would be easy. Unfortunately, no assumptions
> can be made about incoming music except pitched notes would be
> expected. I wasn't looking to extract pitch; just determine onset.
> The usual problem is with slow fade-ins, where some arbitrary start
> point must be decided by when the music level emerges from the noise
> floor.
well, you should still look into pitch detection and note onset detection information from the Music Information Retrieval community. in pitch detection, there is a quantitative measure of the degree of periodicity of the waveform (which is close to 1 as a note is sustained and gets closer to 0 when the note ends and between notes) and there is another quantitative measure called "novelty" which is sorta like the difference between two adjacent frames of the magnitude of the STFT. this is where i would begin to look if i were you.
r b-j
Reply by Eric●March 20, 20172017-03-20
On Sun, 19 Mar 2017 09:37:06 -0700 (PDT), robert bristow-johnson
<rbj@audioimagination.com> wrote:
>On Sunday, March 19, 2017 at 11:53:09 AM UTC-4, Eric wrote:
>>
>> I was wondering about which windows would be best suited to detecting
>> pitched signal within noise, such as musical 'onset detection.' Do
>> you have any opinion on which window types would work well there?
>>
>
>i'm not sure exactly how one uses a window to detect note onsets.
Well, I should have stated that more clearly, I suppose. "Windowed
FFT" to attempt to differentiate pitched info from noise.
>but if you're trying to detect notes in the context of other notes playing, or if the note onset is *not* percussive (like say it's a horn or a human voice and they change from C to D in a legato manner), your problem is much, much harder.
>
>sorry for the bad news.
Yeah, a percussive note would be easy. Unfortunately, no assumptions
can be made about incoming music except pitched notes would be
expected. I wasn't looking to extract pitch; just determine onset.
The usual problem is with slow fade-ins, where some arbitrary start
point must be decided by when the music level emerges from the noise
floor.
Assuming that the WIkipedia article's reference to 'dynamic range'
means 'difference between center peak and nearby lobes', I thought
that dynamic range would be a good thing. But the Wiki article goes
on to contradict that:
"At the other extreme of dynamic range are the windows with the
"poorest resolution and sensitivity, which is the ability to reveal
"relatively weak sinusoids in the presence of additive random noise.
"That is because the noise produces a stronger response with
"high-dynamic-range windows than with high-resolution windows. "
Perhaps I'm misunderstanding their definitions for dynamic range and
resolution.
Reply by ●March 19, 20172017-03-19
On Sun, 19 Mar 2017 12:44:38 -0500, Les Cargill
<lcargill99@comcast.com> wrote:
>Eric wrote:
>> On Wed, 15 Mar 2017 08:31:03 -0700 (PDT), robert bristow-johnson
>> <rbj@audioimagination.com> wrote:
>>
>>> On Wednesday, March 15, 2017 at 10:19:41 AM UTC-4, Eric wrote:
>>>> Most software seems to focus on Hann, Hamming, and Blackman windowing.
>>>> From the graphs I've seen, Dolph-Chebychev appears to outperform them:
>>>> https://en.wikipedia.org/wiki/Window_function#Dolph.E2.80.93Chebyshev_window
>>>>
>>>> Anyone know why it isn't featured in DSP texts to the extent of the
>>>> other windows above? Are there drawbacks?
>>>
>>> wide main lobe. (so when you convolve with it, it's a sloppy transition band.)
>>>
>>> r b-j
>>
>> I was trying to judge the responses from Wikipedia's graphs. The main
>> lobe of Dolph-Chebyshev looks similar to Blackman-Harris window.
>>
>> Dolph:
>>
>> https://upload.wikimedia.org/wikipedia/commons/2/2d/Window_function_and_frequency_response_-_Dolph-Chebyshev_%28alpha_%3D_5%29.svg
>>
>> Blackman-Harris:
>> https://upload.wikimedia.org/wikipedia/commons/0/0a/Window_function_and_frequency_response_-_Blackman-Harris.svg
>>
>> I was wondering about which windows would be best suited to detecting
>> pitched signal within noise, such as musical 'onset detection.' Do
>> you have any opinion on which window types would work well there?
>>
>
>I'm not he, but for speech stuff, people tend to use Hilbert
>transforms for "envelope detection". I have yet to do this, so I
>don't know what that means.
There are two basic ways to convert a signal from real to complex;
first, mix it down to complex baseband and filter off the redundant
spectra, or run the real-valued signal through a Hilbert transform to
generate the analytic part. The Hilbert transformer essentially just
rotates the signal ninety-degrees to generate the orthogonal component
of the complex signal.
Both are used frequently and both have their tradeoffs. The Hilbert
transform may add some distortion, but for many applications it is
small enough to be negligible. Mixing to complex baseband obviously
changes the frequency indexing, so one has to keep accurate track of
what happens, especially if the intent is to mix it back up to the
original spectrum, which takes more processing.
>Cross correlation is the method of choice for pitch detection
>itself. Obviously it has delay.
>
>I've used this code already:
>
>https://gerrybeauregard.wordpress.com/2013/07/15/high-accuracy-monophonic-pitch-estimation-using-normalized-autocorrelation/
>
>
>> The Wiki page has some confusing comments about that type of app.
>> It characterizes the rectangular window as having 'poor dynamic
>> range,' But then states:
>>
>> "At the other extreme of dynamic range are the windows with the
>> poorest resolution and sensitivity, which is the ability to reveal
>> relatively weak sinusoids in the presence of additive random noise.
>> That is because the noise produces a stronger response with
>> high-dynamic-range windows than with high-resolution windows. "
>>
>
>I found this interesting:
>
>http://zone.ni.com/reference/en-XX/help/371361H-01/lvanlsconcepts/char_smoothing_windows/
>
>> I was equating their use of 'dynamic range' with heights of adjacent
>> lobes. By 'high resolution', I thought they were referring to width
>> of the main lobe. But perhaps that's not what was intended.
>>
>> In any case, I thought that the wider main lobe of Cheby or Blackman
>> windows would be good for detecting continuous pitched tones, and that
>> broadband nose would be attenuated by the deep rolloff (100+db).
>>
>> But the Wiki page implies the opposite...?
>>
>
>Areas of application bias what things people say about various DSP
>topics.
Absolutely. And often the language and terminology is a bit
different across applications, with terms sometimes getting overloaded
quite a bit. It is good to be as clear as possible when describing
something, and it is good to ask clarifying questions when trying to
understand something. Naturally, things fall through the cracks all
the time.
>I've been re-reading the Rick Lyons book, and this time more of it
>is making it through my thick skull :) It's a book to be read very
>slowly.
The field of DSP is like that. The details matter and there are lots
of them. ;)
---
This email has been checked for viruses by Avast antivirus software.
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> The Wiki page has some confusing comments about that type of app.
> It characterizes the rectangular window as having 'poor dynamic
> range,' But then states:
>
> "At the other extreme of dynamic range are the windows with the
> poorest resolution and sensitivity, which is the ability to reveal
> relatively weak sinusoids in the presence of additive random noise.
> That is because the noise produces a stronger response with
> high-dynamic-range windows than with high-resolution windows. "
>
> I was equating their use of 'dynamic range' with heights of adjacent
> lobes. By 'high resolution', I thought they were referring to width
> of the main lobe. But perhaps that's not what was intended.
>
> In any case, I thought that the wider main lobe of Cheby or Blackman
> windows would be good for detecting continuous pitched tones, and that
> broadband nose would be attenuated by the deep rolloff (100+db).
>
> But the Wiki page implies the opposite...?
>
Areas of application bias what things people say about various DSP
topics.
I've been re-reading the Rick Lyons book, and this time more of it
is making it through my thick skull :) It's a book to be read very
slowly.
--
Les Cargill
Reply by robert bristow-johnson●March 19, 20172017-03-19
On Sunday, March 19, 2017 at 11:53:09 AM UTC-4, Eric wrote:
>
> I was wondering about which windows would be best suited to detecting
> pitched signal within noise, such as musical 'onset detection.' Do
> you have any opinion on which window types would work well there?
>
i'm not sure exactly how one uses a window to detect note onsets.
there's a lot involved in *robustely* detecting note onsets. if the instrument is a plucked or hammered string (or some other resonant body, like marimba/vibes) and is monophonic, you can do some envelope-following and detect sudden onsets of the envelope. and use a pitch detector to decide *what* note had just onset.
but if you're trying to detect notes in the context of other notes playing, or if the note onset is *not* percussive (like say it's a horn or a human voice and they change from C to D in a legato manner), your problem is much, much harder.
sorry for the bad news.
r b-j