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frequency and amplitude measurement

steven mylrea
Prodigy 210 points

Hi,

I'm trying to measure the audio signal input frequency and amplitude. i want to amplify certain frequency ranges based on the amplitude of the signal in those frequency ranges.

currently im using passband filters and wondering if that is the best approach. for the scale of the amplification im using the absolute of the input value from 0-32767 to determine how much amplification to give. 

i dont need to measure the amplitude on a scale. 

is my approach flawed? when i try to change the amplification very fast i get somewhat of a crackle at low frequencies. any suggestions would be great as I am learning lots from modifying the examples.

Thanks,

Steven

  • 0
    TI__Mastermind 35645 points

    Hi Steven,

    We will check and let you know shortly.

    Thanks & regards,

    Sivaraj K

  • 0
    TI__Mastermind 35645 points

    Hi,

    Please ellobroate your application requirement and kindly let us know, which processor you are working into?

    Which TI board or any custom board?

    Which TI sample code are your using or any third party code?

    Kindly provide all details.

    Thanks & regards,

    Sivaraj K

  • 0 in reply to Sivaraj Kuppuraj
    Prodigy 210 points

    hi,

    im using the ezdsp5535 board.

    passband filters from http://www.arc.id.au/FilterDesign.html as the link in the chapter 6 FIR did not work for online filter design.

    I'm looking to know if my approach will work for amplifying certain frequency ranges?

    secondly I'm seeing some distortion when i change the amplification. how can i smooth it when i change the volume? is there a way to overlap at that point so to not hear the change?

    Thanks,

    Steven 

  • 0 in reply to steven mylrea
    TI__Intellectual 1530 points

    Using a passband filter to filter out required frequencies looks fine.

    For the crackling, could it be possible that while using the absolute value for scaling you might be breaching certain thresholds that might be leading to some clipping at the peaks which might be required to be looked into?

    Best Regards.

  • 0 in reply to KRaviS
    Prodigy 210 points

    ok good about the passband filters.

    for the distortion and clipping i have added code so that if i amplify the output i hold that amplification for a variable. this is smooth for the duration but when it transitions i hear major distortion or clipping.

    when i tried to add an acceleration curve both s and linear to make steps in the amplifications i got worse results and major distortion at higher amplifications and the same results at 1x and 2x amplifications.

    the maximum amplification im trying to get right now is 5x.

    if i dont do any acceleration curve its almost like its transition i hear for a short distortion or clipping at that moment. 

    is there other ways to amplify the output on this board besides multiplying the output?