title: Filter for audio signal processing?
body: <p>I would like to ask what is a good filter for audio signal processing, particularly note onset processing?</p>
  
  <p>Particularly, what I need is a filter that makes peaks sharper while smoothing out others, something like in the image below:</p>
  
  <p><img src="https://i.stack.imgur.com/40usO.jpg" alt="enter image description here"></p>
  
  <p>I am not sure if what I need are low/high-pass filters because I know that those filters work in the frequency domain, and I particularly want to work with the time-domain. I am only working on monophonic signals, recorded in .WAV 44.1Khz 16-bit mono format.</p>
  
  <p>Thanks!</p>