What is the role of the dpdt term of the energy equation in the low Mach number hypothesis

[grabtheNS]

hello, i have a question about the energy equation in

fvScalarMatrix EEqn
(

    fvm::ddt(rho, he) + mvConvection->fvmDiv(phi, he)
+   fvc::ddt(rho, K) + fvc::div(phi, K)
-   dpdt

what is the role of the dpdt term , my understanding is that in low Mach numbers, the pressure perturbation is negligible, so the energy effect from pressure is negligible