Construction Features: |
Large reference massInertial mass of 3.5kg Which provides a fixed reference for one side of the piezoelectric transducer. Impedance determining top plateCovered with layers of silicon and butyl rubber, and a 750mg loading mass forming a nominal radius of 96mm against which the Bone Vibrator is held by an applied static load, simulating the normal headband pressure.
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 B&K 4930 Artificial Mastoid and Bone Vibrator |
A transducer
- To convert the mechanical movement (coupled from the bone vibrator to the top plate) to electrical signals. Three Piezoelectric disks are used, these are made from a ceramic material that produces a large voltage when it is flexed, proportional to the rate of mechanical distortion, (refer to the old gas igniter in the back of the kitchen drawer.) This kind of transducer produces an output proportional to the rate of acceleration or dynamic force.
Electrical couplingConnection to SLM by a cable and adapter that replaces the microphone. Clamp arrangement-A means of holding the bone vibrator against the artificial mastoid at a known force or static load. A spring balance and height gauge are used to set the static load after the Bone Vibrator has been temporarily removed so the rubber strips don’t feature in the measurement. The loading arm should be level when the bone Vibrator is in place with the proper load applied (540g, or 5.4N). The spring balance can be hand held, but a stand will provide greater accuracy |
 B&K Mastoid Bone Vibrator clamp setup |