The acoustic performances of building elements such as windows are performed in laboratory according to standards. In addition to the high cost of the experimental tests, the measurements at low frequencies, face some difficulties such as the lack of reproducibility, the diffuseness of the acoustic field and the effect of the modal behaviour of the rooms. To overcome this, a numerical analysis of the transmission loss of a double-glazing structure is developed in this work. To this end, four numerical configurations, based on experimental conditions, are proposed. The differences concern the modeling of the emitting and receiving rooms. The numerical model used for the double-glazing was calibrated through the Experimental Model Analysis. Results show that there is a significant effect of the rooms on the transmission loss at low frequencies and so of its properties such as the acoustic absorption. A comparison with experimental results is also established to validate the chosen configuration with which parametric analyses are carried out, however, results are not presented in this paper.