Sources:

• Make your own vowel resonators: https://www.phon.ucl.ac.uk/home/mark/vowels/ 

• https://musiclab.chromeexperiments.com/Spectrogram/

• https://imaginary.github.io/pink-trombone/index.html?lang=en

• https://wals.info/feature/2A#2/19.3/152.8

• https://theconversation.com/danish-children-struggle-to-learn-their-vowel-filled-language-and-this-changes-how-adult-danes-interact-161143

• https://lingthusiasm.com/post/172352722661/transcript-lingthusiasm-episode-17-vowel

• https://ocw.uci.edu/upload/files/vowels.pdf

• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6124115/

• https://vocology.utah.edu/_resources/documents/how_are_harmonics_produced_titze.pdf

• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4818279/

• https://pubs.aip.org/asa/jasa/article/150/5/3485/900227/The-mechanisms-of-harmonic-sound-generation-during

• https://scholar.harvard.edu/files/adam/files/phonetics.ppt.pdf

• https://pubs.aip.org/aapt/pte/article/61/1/80/2868862/What-gives-musical-instruments-their-sound

• https://iopscience.iop.org/article/10.1088/1361-6404/ab6a63

• https://en.wikipedia.org/wiki/IPA_vowel_chart_with_audio

• https://www.degruyter.com/document/doi/10.1515/9783110820041-021/pdf