I would like to share with all of you this online interactive tool for digital filter design. It is impressive and it is free. You can understand the effect of each pole and/or zero on the magnitude and phase.

I hope you all find it useful.

Enjoy!

Interactive Digital Filter Design Toolbox ...

Looks pretty cool, but is restricted to non-commercial use (as is the tool suggested by asn). Does anyone know of a really free (as in free for all uses) filter design tool?

As a professional the biggest problem for me is not so much the price, but if I want to buy a rather expensive tool, I will have to get permissions by superiors who will ask questions like: What do you need it for - what are alternatives and so on. And to come up with answers is an effort. A free tool I would just install and time would show if it comes in handy and is used often or not. That's the reason I usually stick with open source (LGPL) tools since they are easy to work with - you just download and use them and don't worry about use-cases.

I realize I could also just use the "free" version advertized above for commercial uses and noone would know. But as it were my conscience is a little sensitive on that matter...

I am aware of a free Matlab toolbox for decimation filter design. Would that be helpful?!

Micromodeler has the advantage of being web based, but for completeness, please also have a look at this post by Rick Lyons:

https://www.dsprelated.com/showarticle/980.php

Thanka lot for this valuable feedback. It is indeed a very useful article and tool as well.

Is there a handy to start from a unit sample response?

Is there a way to cascade filters or convolve the unit sample responses?

The ASN filter designer has an in built signal analyser and generator, allowing you to generate almost any signal of your choice, including loading your own data. Perhaps this is what you're looking for? The interface is real-time, so you can modify the poles-zeros etc and see the effects on the filtered data instantly.

Really nice.

How can I delete a zero or a pole ?

Y(J)S

I would say reduce the filter order manually.

How would that delete a particular zero or pole (rather than whatever happens to be listed as the "last" one) ?