MATLAB and digital filters

[Hannes82]

Hello folks,

I am a student from Austria (Vienna) and currently working on a listening test for a college project. Therefore i need a few shelf filters with some "special features", so i need to program them myself (in MATLAB). But as i am a musician with absolutely no ideas about DSP, i could need a helping hand. I am sure, that it isn't that much work for somebody who is interested in DSP: I already have some files and i just need somebody who would correct them and who is explaining me some points here and then.

As it is a college work, it would be great, if you would be a professional, so i can't quote you here and then in the work

But i am thankful for any kind reply

Thank you and greetings from Austria,

Hannes

P.S.: You can send me an email using the forum. thx

[cdrue]

Hi Hannes,

You could use the fdatool which is a filter design tool in the signal processing toolbox. You can design the (static) filter and export the filter coefficients as far as I remember. You could then use functions such as conv() (convolution) or filter() to apply the filter to a signal.
What are the special features you need for your filter?

Cheers

Carsten

[Hannes82]

sorry for the late reply, i didn't have the chance to check my e-mails. thank you for your hints, i am still trying to learn more about DSP, which isn't easy at all (i never liked math ). I am reading "the scientist and engineer's guide to digital signal processing" which is indeed very helpful for a newbie like me.

the filters are needed to simulate the effects of the human head on higher frequencies. which means, that frequencies above 700Hz are attenuated by 1 - 2 db. I need them as a matlab file, because the program i am using, needs .mat files. The experiment doensn't need real time processing, so i thought, linear phase FIRs (like an allpass when i am right) would be a good idea. And i also got the hint, that it would be perfect to use windowed-sinc filters.

But as i am a newbie, this is a bit of an overkill, because i have to read and read just to know, what would be the "best" filter for that experiment.

Can one say for example, that let's say a blackman window is better for transients? (drums, percussion etc.). I know, there are many basic questions, but it isn't easy to find such information without tons of maths.

Thanks again for the help,

Hannes

[cdrue]

Hi Hannes,

Interesting project you are working on.
I am also interested in audio and acoustics and I am just working on my M.Sc.

Well, as I have not really inverstigated HRTFs, I would like to know which filter behaviour is given in the stop-band. Does it need to be constant or does it contain comb-filter effects?
I could imagine that there are a lot of interfering reflections at the pina to the input of the ear canal and also the ear canal itself shows behaviour of a wave tube terminated by the ear drum which contains poles (in real resonant peaks).
Do you have a reference of the filter function you need?

Regards,

Carsten

[Hannes82]

AUTO-ADMIN: Non-MP3, WAV, OGG, SoundCloud, YouTube, Vimeo, Twitter and Facebook links in this post have been protected automatically. Once the member reaches 5 posts the links will function as normal.

Hi Carsten,

It isn't really that sort of project, although it is very similar to the methods some people are using for transaural processing (binaural stereo). I am using an Surround Sound System, based on the ideas of a guy named Michael Gerzon. His idea, called Ambisonic, is able to reproduce even 3d sound, but unfortunately it's still not a common system (although already invented in the 70's). One part of Ambisonic is the use of shelf filters in the decoder, which are (my project wants to prove that) able to reproduce the sound more realistic. But there aren't many decoders out there, and the ones, that were available in the 80's are analog and didn't had the option to bypass the filters.

Nowadays, these things shouldn't be a problem using software and as some guys stated, that shelf filters don't have an effect and some stated, that there IS an effect when it comes to transients, i simply want to test it out

But i have to admit, till now, i just used EQs and stuff, but never played with the idea, to CREATE them, so it isn't that simple for me.

By the way, i think there are projects which are using HRTF's to combine binaural ideas with ambisonic. So if you are interested this page could be interesting www.ambisonic.net (http://www.ambisonic.net)