Missing the startup chime on your late-model Mac?
Try this Terminal command:
sudo nvram StartupMute=%00
It works on my 2019 iMac, and reportedly also on the 2017 iMac, 2018 Mac mini, 2018 MacBook Air, 2018 MacBook Pro and 2019 MacBook Pro.
To turn off the chime, the command is:
sudo nvram StartupMute=%01
For more hints and tips see AUSOM News, April 2020