ROADMAP
From hearing sound to reading a spectrum
Five stages and 23 steps. The first time through, go in order; when reviewing, jump into any stage.
Lessons 01—05
Sound and digital recording
5 steps
01What does a program have to get past before it can tell classical, jazz and rock apart?02How is sound made, and how does it become the line you see in a recording?03The volume meter hasn’t moved, so why does another song sound clearly louder?04How does continuous sound become a list of numbers, and then turn back into sound?05What should we compute from a recording and hand to the program? Five dimensions of audio features
Lessons 06—10
Cutting a recording into pieces you can compute with
5 steps
06From a whole recording to a list of comparable numbers: what steps lie in between?07Without any frequency analysis, what can the curve alone tell us?08Turning the amplitude-envelope formula into code that actually runs09Call the library first, write it by hand second, then make them agree10How does a computer find which high and low components a single curve is made of?
Lessons 11—15
From waveforms to time and frequency
5 steps
11How can one number hold both “how strong” and “where it starts”?12Writing “how strong” and “where it starts” into a single coefficient13A computer only has a finite number of values. How can it do a Fourier transform?14Reading the spectrum of real sounds in Python: why do four sounds look so different?15Why a whole-clip spectrum can’t tell when a sound happened: the short-time Fourier transform
Lessons 16—20
Shaping spectra into model input
5 steps
16Same numbers, but you only see them when you draw them differently: plotting a spectrogram in Python17Re-marking the frequency ruler to match how we hear: the mel scale18The shapes match, but every number is different: extracting a mel spectrogram in Python19Separating who is making the sound from which sound they make: what MFCCs are20The four steps one line of code does for you: getting MFCCs in Python
Lessons 21—23
Summing up a spectrum in a few numbers
3 steps