On 20 Sep, 05:19, Vladimir Vassilevsky <nos...@nowhere.com> wrote:> Rune Allnor wrote: > > On 18 Sep, 20:28, Piotrek �elechowski <pezel...@gmail.com> wrote: > > >>In few words - It receives sound from room via microphone, filters by > >>pass band filter (tuned on resonance frequency of room) and > >>transmitting via speaker sound in opposite phase. > > > ... > > >>So I am looking for some structure/algorithm which help to correct > >>phase in full pass band (it must have opposite phase characteristic to > >>characteristic of filter to provide constant phase). > > > The problem is that the 'true' source and your cancelling > > source are located at different positions, > > Dr. Rune, cancellation is a different problem, which is indeed > difficult. However the OP is talking about the active damping of the Q > of the room. At low frequencies, the room acts as a cavity resonator. > You only have to damp the most pronounced resonant modes; this is quite > feasible.How is 'damping' different from 'cancellation'? Rune
phase corrector / filter with arbitrary phase and amplitude / designer tools
Started by ●September 18, 2009
Reply by ●September 20, 20092009-09-20
Reply by ●September 20, 20092009-09-20
Rune Allnor wrote:> On 20 Sep, 05:19, Vladimir Vassilevsky <nos...@nowhere.com> wrote: > >>Rune Allnor wrote: >> >>>On 18 Sep, 20:28, Piotrek �elechowski <pezel...@gmail.com> wrote: >> >>>>In few words - It receives sound from room via microphone, filters by >>>>pass band filter (tuned on resonance frequency of room) and >>>>transmitting via speaker sound in opposite phase. >> >>>... >> >>>>So I am looking for some structure/algorithm which help to correct >>>>phase in full pass band (it must have opposite phase characteristic to >>>>characteristic of filter to provide constant phase). >> >>>The problem is that the 'true' source and your cancelling >>>source are located at different positions, >> >>Dr. Rune, cancellation is a different problem, which is indeed >>difficult. However the OP is talking about the active damping of the Q >>of the room. At low frequencies, the room acts as a cavity resonator. >>You only have to damp the most pronounced resonant modes; this is quite >>feasible. > > > How is 'damping' different from 'cancellation'?You only have to consider few modes of the lowest orders, you don't worry about the interference pattern, the criteria is the gross energy rather then SPL at particular location. Vladimir Vassilevsky DSP and Mixed Signal Design Consultant http://www.abvolt.com
Reply by ●September 20, 20092009-09-20
>There is no way to >decrease a lag with a filter. Filters can only /add/ delay.Maybe is it possible to increase lag but in way which gives result similar to decrease but on the next period of signal ?? Something like that (http://obrazki.elektroda.net/39_1251985087.jpg)>Can your problem be solved by adding controlled amounts of delay? if >not, i don't see a solution.I�ve tried that. It would help only if I could add different amount of delay to each frequency in pass band (but It would be difficult and costs a lot of calculating power of processor)>The first step is to come up with a precise statement of >the problem to be solved and the characteristics of an >acceptable - not ideal - solution.I will try to make more measuring and write it more precise, however I think that the idea of problem is clear (?)
Reply by ●September 20, 20092009-09-20
Piotrek Żelechowski wrote: You are replying to Vladimir's post and to my words.>> There is no way to >> decrease a lag with a filter. Filters can only /add/ delay. > > Maybe is it possible to increase lag but in way which gives result > similar to decrease but on the next period of signal ?? Something like > that (http://obrazki.elektroda.net/39_1251985087.jpg)A linear system can't treat one cycle differently from another.>> Can your problem be solved by adding controlled amounts of delay? if >> not, i don't see a solution. > I’ve tried that. It would help only if I could add different amount of > delay to each frequency in pass band (but It would be difficult and > costs a lot of calculating power of processor)Different delays at different frequencies is called dispersion. Avoiding it costs calculating power. Getting it the way you like may cost too.>> The first step is to come up with a precise statement of >> the problem to be solved and the characteristics of an >> acceptable - not ideal - solution.Remember: adding delay to a feedback system rarely makes it more stable.> I will try to make more measuring and write it more precise, however I > think that the idea of problem is clear (?)Think in terms of possibly variable time delay, rather than phase shift. Negative delay can not usually be achieved. Jerry -- Engineering is the art of making what you want from things you can get. ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
Reply by ●September 21, 20092009-09-21
> A linear system can't treat one cycle differently from another.I meant that for example 370� of delay is similar to 10� lead. And I would like to use this effect. But I have to find tool which allow me to design filter with arbitrary amplitude and phase
Reply by ●September 21, 20092009-09-21
> A linear system can't treat one cycle differently from another. >I meant that for example 370� of delay is similar to 10� lead. And I would like to use this effect. But I have to find tool which allow mi to design filter with arbitrary amplitude and phase
Reply by ●September 21, 20092009-09-21
On 22 Wrz, 00:48, Piotrek �elechowski <pezel...@gmail.com> wrote:> > A linear system can't treat one cycle differently from another. > > I meant that for example 370' of delay is similar to 10' lead. And I > would like to use this effect. But I have to find tool which allow mi > to design filter with arbitrary amplitude and phaseSorry for accidentally duplicated And there is some mistake not 370' but 350'
Reply by ●September 21, 20092009-09-21
On 22 Wrz, 00:48, Piotrek �elechowski <pezel...@gmail.com> wrote:> > A linear system can't treat one cycle differently from another. > > I meant that for example 370' of delay is similar to 10' lead. And I > would like to use this effect. But I have to find tool which allow mi > to design filter with arbitrary amplitude and phaseSorry for accidentally duplicated And there is some mistake not 370' but 350'
Reply by ●September 21, 20092009-09-21
Piotrek Żelechowski wrote:> On 22 Wrz, 00:48, Piotrek Żelechowski <pezel...@gmail.com> wrote: >>> A linear system can't treat one cycle differently from another. >> I meant that for example 370' of delay is similar to 10' lead. And I >> would like to use this effect. But I have to find tool which allow mi >> to design filter with arbitrary amplitude and phase > > Sorry for accidentally duplicated > And there is some mistake not 370' but 350'A real lead involves predicting the future. I don't know how to do that. Jerry -- Engineering is the art of making what you want from things you can get. ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
