Modifying the gain of fir1 filter

I'm am creating a FIR equalizer. However I am having trouble modifying the gain of individual filters. I have attempted multiplying the output by a decimal. How would I approach this?

Answer 1

[Star Strider]

I would scale the denominator of the transfer function. If ‘hh’ is your filter numerator, and ‘y’ is your signal, you can increase the gain of the filter by 10 with a denominator value of 1/10:

yf = filtfilt(hh,0.1,y);

I tried this and it works. I’ll post the full code if you would like.

[simply cambio]

Thank you for responding! I have two concerns: 1)Can "y" be an audio file? That's how I am testing that the equalizer works currently. 2) once I create all filters, can I sum the outputs using arithmetic addition?

[Star Strider]

My pleasure!

1. The ‘y’ vector (or matrix) can be anything you want. Note that sound matrices (audio files) are typically (Nx2), with column #1 being the left channel and column #2 being the right channel. I would follow that convention in creating your sound files. Note that this allows you to apply different equalizations to each channel if you want to create some interesting effects.
2. Yes. You might have to multiply by the sum of the individual filter gains (the denominator values) to ‘re-normalize’ the signal. That would avoid distortion if you then want to use the sound function to listen to them. (It might not be a consideration for soundsc.)

You will probably have to experiment. I’ve not done spectrum equalization, so I’ll be learning along with you if you need further help on this project. It should be interesting.

[simply cambio]

Thanks a lot Star Strider! Ill try to implement this shortly.

[Star Strider]

My pleasure!

If my Answer solves your problem, please Accept it!