Acoustic Impedance from Motional Impedance Diagrams

When an acoustic load is coupled to an electromagnetic transducer through a length of air column, there is a critical length at which an increment in acoustic load produces a maximum increment in electrical impedance. The method described makes use of this critical coupling to obtain an optimum precision in determining an acoustical impedance. It is noteworthy that the value of the characteristic impedance of the air column is not assumed but is directly measured.