Well without the humorous size difference, this is basically what whales and elephants do for long distance communication.

Was playing around with a fundamental frequency calculator [0] to associate certain sizes to hertz, then using a tone-generator [1] to get a subjective idea of what it'd sound like.

Though of course, nature has plenty of other tricks, like how Koalas can go down to ~27hz. [2]

[0] https://acousticalengineer.com/fundamental-frequency-calcula...

[1] https://www.szynalski.com/tone-generator/

[2] https://www.nature.com/articles/nature.2013.14275

How long would a Dachshund have to be for it to sound like a 60 kilo Great Dane?

Sounds like an antenna, if you'll accept electromagnetic noise then there are some fish that could pass for your shrew, e.g. https://en.wikipedia.org/wiki/Gymnotus

I’m not sure exactly how, but cats can emit a surprisingly low growl when they want to. Like, as deep as a large human would be able to. So there’s more going on than just linear size… And how I’m wondering what the lowest recorded pitch made by a shrew is.