terminal – Has the Unix parameter name SystemAudioVolume in El Capitan been changed to SystemAudioVolume DB?

I try to change the start tone. When I checked the setting with:

sudo nvram -p

A setting for SystemAudioVolume DB% ee is returned

I entered:

    sudo nvram SystemAudioVolume=%00

If I check that again with sudo nvram -p

Both names appear in the list:

SystemAudioVolume DB ….% ee

SystemAudioVolume ….% 00 (accepted my setting but did not stop the sound)

Should I try to set SystemAudioVolume DB instead?

If so, is that the right way?

sudo nvram SystemAudioVolumeDB=%aa

(No place in front of DB.) Does anyone know the right area for it?
My computer is old, but I do not want to break it.