Lithium-ion batteries have become a ubiquitous energy source for applications ranging from cell phones to battery-powered electric vehicles. Despite this success, state-of-charge (SOC) and state-of-health (SOH) estimation remains challenging, particularly in applications requiring high numbers of cells like battery electric vehicles. Often the operating conditions and released capacity of individual cells in a pack are not directly monitored. Inaccurate estimates of cell SOC or SOH can lead to overcharge or overdischarge which could result in thermal runaway. This work explores the relationship between the modal response of a clamped-clamped 10 Ah NMC/graphite pouch cell and its SOC and SOH. We employ scanning laser Doppler vibrometry on a cell at 0\% and 100\% SOC for over 80 charge-discharge cycles. Electrochemically-induced mechanical property change is reflected in the shift in resonance frequency and the magnitude of the transmissibility curve at resonance. We also present an effective medium model (EMM) of the cell based on multiscale homogenization for use in finite-element software to simulate the cell’s modal response as a function of SOC. Results indicate that modal analysis can be used to estimate cell SOC and SOH, while the EMM provides insight about which cell components contribute to the cell’s dynamic mechanical response.