Accurate experimental measurement of the input impedance was first achieved by closing the mouthpiece with a flat plate containing a small capillary and a microphone [3,4,5]. The capillary feeds a known sinusoidal volume velocity into the mouthpiece and the microphone measures the pressure response. The input impedance is deduced from the ratio of the measured pressure and volume velocity. We call this a frequency domain experiment since it must be repeated for each frequency of interest. Recent developments in the field of frequency domain excitation include the use of a chirp signal which consists of a sinusoid of rapidly changing frequency. All frequencies of interest may then be measured in a short time interval.

Jonathan Kemp 2003-03-24