> For the complete documentation index, see [llms.txt](https://lcav.gitbook.io/dsp-labs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://lcav.gitbook.io/dsp-labs/filter-design.md).

# 4. DIGITAL FILTER DESIGN

In the previous exercise, we used a very simple filter in order to remove the DC offset. Although the applied filter does the necessary job, it also removes frequencies of interest! Try running the Python script with and without this simple high pass filter (HPF), and you'll notice a lot of the lower frequencies of the voice are removed when applying this filter.

This motivates the design and use of a filter with a sharper [slope/roll-off](https://en.wikipedia.org/wiki/Roll-off). In this chapter, we approach this task in order to replace the simplistic filter used earlier. After all, no DSP module is complete without a section on filter design!

As before, text contained in highlighted boxes are tasks for ***you***!

{% hint style="info" %}
TASK: This is a task for you!
{% endhint %}


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