Click here to purchase the entire book in PDF format. Pressure Transducers Remember that a pressure transducer is basically a sealed can, just like the coffee can barometer described in Section 6.7.1. Therefore, any change in pressure in the outside world results in the displacement of the diaphragm. High pressure pushes the diaphragm in, low pressure pulls it out. Unless the change in pressure is extremely slow with a period on the order of hours (which we obviously will not hear as a sound wave - and which leaks through the capillary tube) then the displacement of the diaphragm is dependent on the pressure, regardless of frequency. Therefore a perfect pressure transducer will respond to all frequencies similarly. This is to say that, if a pressure wave arriving at the diaphragm is kept at the same peak pressure value, but varied in frequency, then the output of the microphone will be a voltage waveform that changes in frequency but does not change in peak voltage output. A graph of this would look like Figure 6.114. Figure 6.114: The frequency response of a perfect Pressure transducer. Note that all frequencies have equal output assuming that the peak value of the pressure wave is the same at all frequencies.