An
ear canal pressurization device optimized for aural acoustic
immittance testing is disclosed. The preferred embodiment of the device is comprised of a rigid mounting framework which holds in position, axially aligned, a first flexible chamber
assembly, a centrally disposed forcer
assembly, and a second flexible chamber
assembly. The forcer assembly comprises a ferromagnetic
bobbin and coil that provides
electromotive force for a
moving magnet linear motor. The motor is comprised of a rigid chamber link, which passes through the
hollow core of the
bobbin, with a ferromagnetic keeper
washer and axially aligned
rare earth ring
magnet at either end, with like
magnetic poles facing each other. The motor is elastically suspended between the first and second flexible chambers. Current flow through the coil of the forcer assembly provides motive force for the motor via attraction or repulsion of the motor magnets and movement of the motor increases the volume of the first flexible chamber while decreasing the volume of the second flexible chamber, or vice versa. The internal volume of the first flexible chamber is coupled via an
air line to an
ear canal and through a controlled valve to a small vent, and the internal volume of the second flexible chamber is vented to
ambient air pressure. Changes in volume of the first flexible chamber, due to
motor movement, produce changes in
ear canal pressure re Boyle's law. The vent may be opened to allow ear canal pressure to gently equalize to
ambient air pressure or to generate ear canal pressure sweeps free of pressure baseline offset. The vent may be closed to set a static ear canal pressure or to generate ear canal pressure sweeps with an incidental baseline offset. The vent may be controlled to generate ear canal pressure sweeps with an intended baseline offset. The device produces ear canal pressure proportional to drive
voltage, so any desired pressure versus
time function can be generated by applying a coil driving
voltage with the appropriate amplitude versus
time function. The device operates quietly to avoid interference with aural acoustic
immittance measurement, and should have a long and maintenance free
life span.