Andor, I always used to think that the purpose of an audio equalizer is to compensate the transfer function nulls with the poles and the poles with the nulls in the way that the resultant overall response is flat. In this context it does not make sense to talk about the phase linearity of an equalizer itself. However the technical arguments are meaningless in the fields of religious wars of audiophiles. Vladimir Vassilevsky DSP and Mixed Signal Design Consultant http://www.abvolt.com Andor wrote:> > Perhaps you'll find this useful: > http://www.weiss.ch/eq1/images/brochureEQ1-LP.PDF > > If you skip the nice pictures, you'll get some information on the > second page. It also offers an oppinion on why FIR filters are > unsuited for audio equalization. > > In another thread I posted this link: > http://www.audiosignal.co.uk/Gerzon%20archive.html > > Also an interesting read when discussing linear vs. minimum phase for > audio. > > Regads, > Andor
DSP sound/audio demos
Started by ●November 16, 2003
Reply by ●November 17, 20032003-11-17
Reply by ●November 17, 20032003-11-17
Matt Timmermans wrote:> "Jerry Avins" <jya@ieee.org> wrote in message > news:bp8sn0$cul$2@bob.news.rcn.net... > >>robert bristow-johnson wrote: >>Those things are still widely used. CCD imaging arrays shift the pixel >>information out that way. [...] > > > How does that work? The only way I can think of needs inductances.Hmmm ... "Charge coupled device." Charge is transferred from bucket to bucket along a chain. One configuration of video CCDs alternates rows of light-sensitive buckets and data shifters. (Non-sensitive buckets simply covered over with metalization.) After a suitable integration interval, charges are shifted (simultaneously) from the detectors to the bucket-brigade chain, and then moved along the chain to the output node. Clever! See http://www.extremetech.com/article2/0,3973,1157574,00.asp Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●November 17, 20032003-11-17
Rick Lyons wrote: ...> Hi, > we used to use linear-array CCDs, along with a laser > and Bragg cell, to perform spectrum analysis. > (It worked because a glass lens performs a Fourier > transform, I think.) > > Don't remember all the numbers but we could perform > spectrum analysis of a signal whose bandwidth was, say, > 5 Mhz (this was back when A/Ds could only sample > at a few MHz/sec rate). The spec resolution was, say, > 5/4000 MHz. The neat part was that the spectral > results where updated at, say, a 10 kHz rate. > > All in analog! > > The above numbers may be "way off", but > at that time, no DSP system could > even come close to such a wideband, high-speed, > spectrum analyzer. > > See Ya', > [-Rick-]The first processors for side-looking radar used lenses the same way. One of the lenses was a cone. The shape was originally derived from the required Fourier transformation properties, but a simpler way to see it is as an optical focuser whose focal length decreases as the beam angle tilts down. Just the thing to project a distorted map on a vertical surface to a justified horizontal one. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●November 17, 20032003-11-17
Vladimir Vassilevsky wrote:> ... the technical arguments are meaningless in > the fields of religious wars of audiophiles. >... Before discussing technical audio issues, I try to learn if my interlocutor believes that speakers sound better when driven through gold-plated welding cable. I don't engage him if he does. Another disqualifier is ownership of a CD demagnetizer. (I hadn't heard of those until Clay pointed them out.) Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●November 17, 20032003-11-17
On Mon, 17 Nov 2003 13:10:28 -0500, Jerry Avins <jya@ieee.org> wrote:>>Before discussing technical audio issues, I try to learn if my >>interlocutor believes that speakers sound better when driven through >>gold-plated welding cable. I don't engage him if he does. Another >>disqualifier is ownership of a CD demagnetizer. (I hadn't heard of those >>until Clay pointed them out.)Don't forget the cryogenic CD freezer. Greg Berchin
Reply by ●November 17, 20032003-11-17
It might be easier to use a sound editing program such as Cool Edit to do your demo. They have interesting sounding effects already coded and the interface is very easy to use. I did a demo for 1st graders using a sound editing program on a Mac a few years ago and they seemed to enjoy it. "Rune Allnor" <allnor@tele.ntnu.no> wrote in message news:f56893ae.0311160456.20f2d245@posting.google.com...> Hi All. > > The last few weeks I have been asked by a few people (neighbours, > neighbours' kids) what I do for a living. And I find that it's not > easy to explain verbally what DSP is about. Terms like "Discrete > Fourier Transforms", "Singular Value Decompositions", "Rayleigh waves" > and the likes don't do much for lay people, except perhaps establishing > or reinforcing my already firm reputation as "the mad scientist" of the > neighbourhood. > > So, inspired by this and some remarks Al Clark made in the DSP bookthread,> I've started thinking what demos could be useful to show people what > at least parts of DSP is about. I assume I have a laptop PC available > where matlab is installed and that has a microphone and a sound recording > program. With this system I can record somebody speaking a sentence, > store the sound to a .wav file that I load into matlab. I then manipulate > this sound by means of DSP in matlab, and play the manipulated result over > the PC speaker or headphones. > > So, what DSP demos could be included here? Remember, I'm not an audio > specialist so the most psycho-acoustical stuff would probably best be > left out. Implementations should not be too difficult either, or at > least good algorithm recipes should be available. Pitch shifting? > LPC-errors (somebody told me these things sound like "robot voices" > from a 1977 sci-fi movie)? Adding echos/reverbrations? Other things? > > Rune
Reply by ●November 17, 20032003-11-17
I have a guitar amp that has a chorus effect built from a bucket brigade device. I think it is 80's vintage. Turning on the chorus definitely adds some noise to the output... "Clay S. Turner" <physics@bellsouth.net> wrote in message news:ov4ub.48193$a7.37002@bignews3.bellsouth.net...> Hello Richard, > > These devices have been around for awhile. I use to get them at RadioShack> back during the '70s. If you remember the "echoplex." It was an audio tape > delay whose output was fed back to its input. The read head was on aslider> and you could move it back and forth to change the delay. A friend and I > made some digital versions using the SAD devices. They worked okay. Backat> least the tape loop didn't wear out. > > Here's a description of a SAD device: > > http://www.geofex.com/sad1024.htm > > > Clay > > > > "Richard Dobson" <richarddobson@blueyonder.co.uk> wrote in message > news:42Utb.219$537.128@news-binary.blueyonder.co.uk... > > Thanks for this very useful and interesting information. I hadn'tthought> of the > > bucket-brigade device in this context, maybe it's the exception that > proves the > > rule? > > > >
Reply by ●November 17, 20032003-11-17
Vladimir Vassilevsky wrote:> Andor, > > I always used to think that the purpose of an audio equalizer is to > compensate the transfer function nulls with the poles and the poles with > the nulls in the way that the resultant overall response is flat.I'm not quite sure what you mean - which zeroes and poles do you want to compensate? Audio equalisation as I see it refers to changing spectral balance ("timbre") of musical (or perhaps motion picture) material. It can be used correctively or artistically, and is usually the domain of live and studio recording, mixing and mastering engineers. Heck, it's what you do when you crank up the bass on your stereo - just a little more sophisticated, depending on the device you use.> In this context it does not make sense to talk about the phase linearityof> an equalizer itself. > However the technical arguments are meaningless in > the fields of religious wars of audiophiles.Whatever. Regards, Andor
Reply by ●November 17, 20032003-11-17
Andor wrote:> Vladimir Vassilevsky wrote: > >>Andor, >> >>I always used to think that the purpose of an audio equalizer is to >>compensate the transfer function nulls with the poles and the poles with >>the nulls in the way that the resultant overall response is flat. > > > I'm not quite sure what you mean - which zeroes and poles do you want to > compensate? Audio equalisation as I see it refers to changing spectral > balance ("timbre") of musical (or perhaps motion picture) material. It can > be used correctively or artistically, and is usually the domain of live and > studio recording, mixing and mastering engineers. > > Heck, it's what you do when you crank up the bass on your stereo - just a > little more sophisticated, depending on the device you use. > > >>In this context it does not make sense to talk about the phase linearity > > of > >>an equalizer itself. >>However the technical arguments are meaningless in >>the fields of religious wars of audiophiles. > > > Whatever. > > Regards, > AndorThe goal among purists -- they have good justification -- is to make the reproduced sound as close to what was recorded as possible. So the poles and zeros in question are those of the listening location and the reproducing devices. There is something to be said for second guessing the mixing engineer, but usually, not much. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●November 18, 20032003-11-18
Andor wrote:> > > I always used to think that the purpose of an audio equalizer is to > > compensate the transfer function nulls with the poles and the poles with > > the nulls in the way that the resultant overall response is flat. > > I'm not quite sure what you mean - which zeroes and poles do you want to > compensate? Audio equalisation as I see it refers to changing spectral > balance ("timbre") of musical (or perhaps motion picture) material.There is no need to change the timbre. The timbre is not going to be any better then originally designed by the professional sound producer. All you have to do with an equalizer is compensate the major non-idealities caused mainly by the speakers and the acoustic environment.> It can > be used correctively or artistically, and is usually the domain of live and > studio recording, mixing and mastering engineers.Using the equalizer either creatively or correctively requires taking measurements and having at least professional-like experience. There is no way an amateur can tune correctly 31-band 1/3 octave or 5-band parametric equalizer by perception.> Heck, it's what you do when you crank up the bass on your stereo - just a > little more sophisticated, depending on the device you use.Most of people are just making a V-shaped equalization curve boosting high and low frq. The result is an awful sound. VLV
