Audio processing systems tend to use really a lot of math to massage the data and infer information from raw streams. VB.NET might not be the best platform when it comes to using math and input API s that produce high quality results and performance.
Signal processing is significantly more complicated that just applying algorithms in the hope that the application works. You really need to plan what you want to do, how to proceed and most important, how to test your results to verify the usefulness of the program.
Getting input from a microphone is fairly simple. Analysing the raw wav can be made to be simple if you can identify key characteristics of a babies cry. Record babies crying. Whats common ? Is it a change in pitch , duration ? Once you know what is common, then search for an algorithm that can identify that change in a series of changing values. There are A LOT of algorithms that can find range of changes in series of numbers.