An active respiratory therapeutic device for clearing breathing passages, loosening and breaking up mucus plugs and phlegm in a patient's sinuses, trachea, bronchial passages and lungs while a patient is breathing normally through the device is disclosed. The apparatus preferably includes a C shaped curved hollow housing having a closed end portion and an open threaded end portion. The open end portion forms at least part of an acoustic coupling chamber. A generally funnel shaped tapered mouthpiece tapers to a small end portion sized to be inserted into a patient's mouth. The mouthpiece forms another part of the acoustic coupling chamber. An acoustic signal generator housed within the hollow housing generates and directs acoustic vibrations into and through the coupling chamber. The mouthpiece preferably includes a valve permitting a patient breathing through the mouthpiece to inhale through a valve opening and exhale through a bypass passage around the valve while at the same time coupling the acoustic coupling chamber into the patient's airways.