What are you writing? A letter to the president. What about? The usual... Introducing myself. Asking about his day. Seeing if he'll change the sound that fire sirens make.
Sirens wail up and down so that people with high frequency hearing losses (the most typical kind) can hear them at the down end and people with mid-range-frequency, noise-induced hearing loss can hear them at upper and lower end.
Sirens wail up and down so that people with high frequency hearing losses (the most typical kind) can hear them at the down end and people with mid-range-frequency, noise-induced hearing loss can hear them at upper and lower end.