The unit of sound pressure, the acoustic pascal is not defined in any standard in the area of sound-in-air metrology. Instead, the required parameter is the device sensitivity which is ex-pressed in decibels and is traceable though standards that rely on the existence of physical acoustical artifacts. However, the acoustic pascal has been experimentally realised using optics and is shown to be traceable through the metre, second and the kilogram. The definition of the kilogram in 2019 through fundamental constants, will allow all three aforementioned units to be traceable through quantum approaches and photon correlation will allow the definition of the acoustic pas-cal traceable through these three units in a direct and absolute manner without the reliance on physical artifacts.
