> I considered a few encoding options for compressing the audio.

The presentation of this part seems extremely padded out to me, ironically enough.

Programmers made 8 bit micros talk in the 1970s, using nothing but square wave pulses sent to the speaker.

First I thought you made a lecture on MCUs which was available for viewing in exchange for $0.10

Then I thought you made a lecture on MCUs where the device was available for purchase generally for $0.10.

Then I thought with an MCU valued at $0.10 you generated speech

English... sigh

Can you export the schematic and Gerber files to a PDF file? A lot of open source projects do this, and it makes it much easier to tell what's going on, with software pretty much everyone already has on their computer.

And most code is in C++, while I was expecting straight Assembly, pleasently surprised.

Have you tried just savimg the zero crossing times?

From distant memory you got quite a bit more compaction.