I’ve written two articles about this work, one for UK teachers and one for US teachers.
Although the core idea is the same in both cases, they are different and if you have got this far then I suggest it’ll probably be worth reading them both. Click the bird for the UK PDF and the US bird will generate an email to ask nicely.

UK Teachers
Using birdsong to support the teaching of sound and graphs
School Science Review (Volume 96, Issue 356) March 2015 (you might need to right click and save as..)

US Teachers
Physics and Birdsong: “Listening” with Graphs”
The Physics Teacher (Vol.57, Issue 6) September 2019
URL: https://doi.org/10.1119/1.5124271
DOI: 10.1119/1.5124271