Late 2016 Mac models and newer do not have a startup chime.  Apple also removed the BootAudio NVRAM parameter from the 2017 iMac models (no more hacks to turn it on).

Apple has revised all of their Knowledge articles to reflect this change.  For example, their How to reset NVRAM article now says “Shut down your Mac, then turn it on and immediately hold down these four keys together: Option, Command, P, and R. Keep holding the keys for about 20 seconds, during which your Mac might appear to restart. (If you have a Mac that plays a startup sound when you turn it on, you can release the keys after the second startup sound.)”

Bonus trivia: All Mac models manufactured between 1999 and Late 2016 played an F-sharp major chord as their startup chime, and this sound file’s origin was from the Quadra 840AV C major chord startup chime, pitch shifted up to F-sharp major.