noise reduce patch
  • hello there,

    im pretty new to audulus and i am coming across a problem i cant seem to solve :( maybe it isnt even possible....

    i am trying to record something into loopy hd on my ipad and sadly enough i have to use the built in microphone. thing is there is alot of noise coming in also... i would like to built a patch that is subracting the noise from the input... i tried builting a noise node and getting it to output the same values(checkd in value node) and the subtract both signals but this doesnt work... i dont know how to do it...
    i also tried the filter cutoff.. by the way for what are the three inputs on the side? low, mid, high? but it cuts off to much... cant i just sample the noise and use it to clean the frequency... it doesnt have to be perfect, just want to play around a bit, and this seems like a good exercise to get to know audulus...

    can someone help me please?

    thx for taking the time, jaden
  • You're on the right track. Yes you can probably get Audulus to reduce noise but you probably can't do it by phase cancelling the noise with just the iPad mic in. You might want to try gating, downward expansion and EQ to start. The simplest would be a gate which you can create by using the Envelope Follower to let your signal thru based on a threshold setting. Or you could use the threshold to open an ADSR to gate your signal through. These techniques will keep your signal quiet until the gate opens but then you will have noise coming thru with your signal. You can add EQ to the chain to reduce the noise by using the low pass and high pass filter nodes in series and simply setting their frequency controls to creat a band pass filter that filters out everything above or below the range of your audio source. Downward expansion can be created by using the envelope follower to turn down the gain of your signal even more as your signal level drops. There's a pretty easy way to do it using the Mapper node and some math nodes to set the range. And lastly I created a Vocoder patch that could easily be modified to do this in multiple bands to create a multiband noise suppressor. Ultimately though with the iPad even a simple USB condenser mic will make a huge difference. The 3 inputs on the filter are signal in at the bottom, frequency in hertz, so big numbers like 50-8000, in the middle and resonance at the top. I'll throw an example of gating/EQ up so you can see it.
  • hey dcramer,
    thank you very much for your help! i guess I will have to read and research on your answer some time until I completly understand it :) but I certainly would not dismiss some examples :)

    jaden
  • Ok. here's an example of a Noise Gate with filtering being used to reduce noise. This patch works fine on my ipad but didn't want to open on my mac.
    It's very simple; the signal comes in stereo on the left side, then splits to dry and wet and you can adjust which you hear with the Crossfaders on the right. The wet signal goes to a Multiplier Node which works like an amp so you can boost the gain (SENSITIVITY knob) The wet signal then splits, one is our audio signal and one is our control signal. The control signal then goes to the Env Follower which creates a smoothed out signal that follows the volume of the boosted input. That signal goes to a Low Pass filter so it can be smoothed some more (RATE knob) Then the control signal goes to the Mapper which adjust the curve of the gain change, essentially it makes quiet signals be silent. This signal from the Mapper is our control signal and is then used to control the volume of our audio signal by multiplying it in a Multi Node. The audio signal first passes through a Highpass and Lowpass filter to reduce noise by taking out lows and highs, this creates the Bandpass filter, you can adjust the highs in the audio (TONE) and is then gain controlled by the control signal. The VU meters on the end show the reduction, when its high the gain is down and as theVU's drop the gain is coming up. The farthest VU's show the actual output volume. There are Range Nodes at the output stage which are used as hard limiters to limit the final output. You can control the amount of total output and the limiter range with the Makeup Gain and Limiter controls, but keep in mind that if your signal pushes the limiter it will distort. Changing the shape of the Curve Nodes will alter the way the Audio signal is altered by the control signal. Changing the Rate control alters how fast the gate opens and closes, too slow may miss attacks and to fast may create a zipper artifact.

    I tested it on my ipad with the internal mic and it seemed to work pretty good. Keep in mind that this type of noise reduction works by turning down the audio level when the input signal is quiet or silent and turning it up as the signal into the mic gets louder, the theory is that the sound of the signal will mask the background noise. In the old days we used gear like this in rackmount boxes on every signal we recorded to clean up our tracks.
    This patch looks really complex but actually it isn't, firstly i did it in stereo for Audiobus usage so that means there are almost 2 of everything, and secondly most of the nodes in the patch are just math nodes used to set the bias and range of the controls. It would be easy to strip out the knobs and use "set default" to input fixed numbers everywhere. Ideally one could take the guts of this thing and pack it all into a Patch Node so you didn't see it and you just had VU's and knobs on the outside.
    Goodluck
    Stereo Noise Reduction.audulus
    289K
  • Yep, Mac v. 1.6.1 is missing the Range node, hence the crash. I need to do a better job of handling these cases where the Mac and iPad versions aren't quite in sync.

    This beta should load it:

    https://dl.dropbox.com/u/45540223/Audulus/Audulus 1.8 Unsabdboxed Beta 2.zip

    cheers
    - Taylor
  • Crap! I didn't even think of that, of course!
    Hey check it out on an ipad with the internal mic, I was surprised at how well it works.
    I am also working on a 9 band multiband one based on my Vocoder patch that really does the some cool comb filtering effects.
  • @Dcramer, wow! That's really good. I just compared it with the input wired directly to the output... oh now I see you have a wet dry mix knob in there.

    I really need to get some mono/stereo utility nodes in there so you don't have to duplicate everything!
  • ok I cleaned it up and put it in a patch node there's a copy in the effects thread as well for Audiobus users.
    Stereo Noise Reducer 2.audulus
    377K
  • HA! thats just brilliant!!! thanks so much! Its so cool that you explain in detail what you are doing, even though I dont understand everything that you are saying :|
    But I will give this some time and I try to rebuilt this thing and hope I will learn a thing or two :)

    THANK you for your time,

    jaden
  • No problem, I have a better looking version posted in the Audiobus Effects Patch thread and I have a simpler version coming in which I get the same gating effect but in a totally different way!