Filtering data from WAV butterworth - problem

[TomTomTomTomTom]

Hello!!

I have LabVIEW 2013

I´m new in matlab and I have following problem:

I want to filter speech/voice data from WAV file with block Butterworth Filter.vi. I know how load signal with Sound File Read Simple.vi, I know how to get info about file with Sound File Info.vi and I know that I can display waveform data with waveform graph/chart. But i dont know how to correctly set up butterworth filter in to my scheme, or better said how to correctly bring data on it. When I´m trying to display filtered data with waveform chart I only get flat  line.

I have already checked NI Examples (IIR Filter Design, IIR Filtering Using Optional Specs, IIR Filterin and Response, IIR Filter Design). But after that i felt even more stupid and lost.

Does number of channels depends (mono/stero) - do I have to separate it?

Do I have to use some loop?

Second question - How many changes I will have to make when I will want to have real-time filtering with butterworth filter.vi ( for example - with getting data from microphone )

Many thanks!

[srikrishnaNF]

Hi TomTomTomTomTom,

   Please check out the Filter Express VI which is present in the Express>>Signal Analysis pallettes.

Regards,

SrikrishnaNF

[TomTomTomTomTom]

Hello, thank you.

I have tried to use scheme and settings as on picutre. File that I use is speech signal. So when I will set lowpass (below 100 hertz) I should hear no voice. But when I run this program the output signal sound like input but more silent.

Am I missing something?

[GerdW · Accepted solution]

Hi 5 times TOM,

you set a 1st order low pass, so it damps high frequencies with just 20dB/decade. It will NOT clear anything over 10Hz, it will just damp it!

You need to use a higher order for your lowpass filter to effectively cancel higher frequencies!