An apparatus for patient's lung function testing using forced oscillation technique is described. The apparatus includes a sub-woofer configured to generate a pressure wave. The apparatus further includes a waveguide configured to direct the generated pressure wave to be introduced into airflow towards the patient's lung. The apparatus includes a pressure transducer configured to measure a change in pressure of the airflow and one or more flow transducers configured to measure a change in flowrate of the airflow, in response to the pressure wave introduced into the airflow. The apparatus includes a computing unit configured to determine a mechanical impedance of the patient's lung based on the measured change in pressure and flowrate of the airflow.