Attached is some code that may help to get you started.
The code came from this forum topic and there is additional information there:
On 4 June 2015 at 17:24, Annabelle Susan Morison
Hi, it's Annabelle.(setq low-freq 440) ; initial frequency - Hz
I know this might sound strange but, I wonder if there's a way for me to
make a noise generator that generates the four common siren tones, wail,
yelp, hyperyelp, and hi-lo? If there is, what would be the code for me to
make these? Also, being blind, how would I make this into a plugin?