What is the frequency response of the Sinc filter?

Question

Mathematics

Many sigma-delta ADCs contain digital sinc filters of different orders (sinc3, sinc4, for example). At the same time, in the documentation you can usually find the frequency characteristics of the filter in the form of funny pictures like this one:

or this one.

I am looking for a formula for this function, I found several different options, but they do not correspond to what I see on the ADC output. Tell me where to look. Thanks in advance.