Abstract: The invention provides for a method and device for determining a gas pressure and temperature in a hollow space, including a fuel/air mix in an internal combustion engine combustion chamber. According to the invention, pressure and temperature are detected by means of a measuring element (5) of an ultrasound transducer/pressure sensor combined unit, said measuring element acting both as a pressure measuring element and an ultrasound transducer element to determine temperature. Therefor, said measuring element can be operated at given moments, on one hand as a pressure measuring element and on the other hand as an ultrasound transducer element or continuously, as a pressure measuring element, and furthermore as an ultra-sound transducer element superimposed with the latter. In that case, it is provided that signals should be conveniently separated for the measuring element output signal. The invention can be used, for instance, to determine air volumes for car internal combustion engines.