The photoacoustic signal in a closed T-cell resonator is generated and measured using laser based photoacoustic spectroscopy. The signal is modelled using the amplitude mode expansion method, which is based on eigenmode expansion and introduction of losses in form of loss factors. The measurement reproduced almost all the calculated resonances from the numerical models with fairly good agreement. The cause of the differences between the measured and the simulated resonances are explained. In addition, the amplitude mode expansion simulation model is established as a quicker and computationally less demanding photoacoustic simulation alternative to the viscothermal model. The resonance frequencies obtained from the two models deviate by less than 1.8%. It was noted that the relative height of the amplitudes of the two models depended on the location of the antinodes within the resonator.