As a first step toward understanding the electroacoustic response of polyelectrolyte hydrogel nanocomposites, we systematically vary the linear charge density of acrylic acid-co-acrylamide polymer networks (at a fixed total polymer concentration) to ascertain how the charge and mobility affect the electrokinetic sonic amplitude (ESA) spectra. A weakly charged polymer registers a negative ESA (real part), which we attribute to dynamics of the elastic network and its charge, whereas a highly charged polymer registers a positive ESA, attributed to sodium counterions. A mechanistic theoretical model is proposed that attributes the transition to the subtle manner in which the hydrodynamic friction of the network strands scale with their linear charge density. Further insights are gained from the electrical conductivity and dynamic shear moduli (in the linear viscoelastic regime). The electrical conductivity is dominated by the mobility of the sodium counterions and is diminished by network hindrance and counterion condensation, and the storage modulus decreases systematically with the linear charge density, suggesting a dominant role of interchain electrostatics, and possibly electro-steric influence on the polymerization and cross-linking.