ACME Whistle no. 212 sound test

Using Audacity I've recorded a few blows of the ACME 212 Field Trainer whistle.

Spectrum analysis

Conclusion

The strongest frequency is consistenly around 5,000 Hz. The output varies from how strong/soft you blow it, which is not entirely consistent with how ACME advertises it:

With consistent frequency no matter how
hard or soft you blow.