Nothing beats baudline, this has been my go-to signal analyzer tool for decades. It makes me sad that the project has not seen any updates for a long time, and it is getting harder to get it to run proper on a modern OS.
I believe the author considered releasing the source code under some permissive license long ago, but decided not to because the project was refused by freshmeat.
Sigblip: if you read this, please re-consider so baudline can get a second life!
It's bit more geared towards speech analysis for phonetics in linguistic research and education. Solid tool even though the UI is hot garbage. No screenshots, alas.
I believe the author considered releasing the source code under some permissive license long ago, but decided not to because the project was refused by freshmeat.
Sigblip: if you read this, please re-consider so baudline can get a second life!
http://baudline.com/