A significant number of quadrupolar dyes with a D-$pi$-A-$pi$-D or A-$pi$-D-$pi$-A structure, where D and A are electron donor and acceptor groups, were shown to undergo symmetry breaking (SB) upon optical excitation. During this process, the electronic excitation, originally distributed evenly over the molecule, concentrates on one D-$pi$-A branch, and the molecule becomes dipolar. This process can be monitored by time resolved infra-red (TRIR) spectroscopy and causes significant spectral dynamics. A theoretical model of excited-state SB developed earlier ( extit{J. Phys. Chem. C}, extbf{2018}, extit{132}, 29165) is extended to account for the temporal changes taking place in the IR spectrum upon SB. This model can reproduce the IR spectral dynamics observed in the $-mathrm{C}equiv mathrm{C}-$ stretching region with a D-$pi$-A-$pi$-D dye in two polar solvents using a single set of molecular parameters. This approach allows estimating the degree of asymmetry of the excited state in different solvents as well as its change during SB. Additionally, the relative contribution of the different mechanisms responsible for the splitting of the symmetric and antisymmetric $-mathrm{C}equiv mathrm{C}-$ stretching bands, which are both IR active upon SB, can be determined.