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2 Archives of Acoustics

2 1999

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Ultrasonic transducer for the reception of acoustic emission signals of the temporomandibular joint

Salomon R., Lis W., Zienkiewicz J.

Archives of Acoustics

1999

Vol. 24, no. 3

331-364

Auscultation and analysis of acoustic signals emitted by the human body are widely used in medical diagnosing. Acoustic signals are also emitted by joints, including the temporomandibular joint, which is the subject of this paper. A system was developed to receive, record, process and display the signals emitted by this particular joint. The article presents an essential fragment of the system, namely a special ultrasonic transducer designed to receive acoustic signals emitted by the temporomandibular joint. At first, the particular requirements were established in the area of the parameters and functions of the transducer. Following that, a technological solution was proposed. Next, a model of the transducer was analysed using the difference equation method with continuous time. The solution of these equations is the pulse response of the transducer and in the frequency domain, it is the shift function. These functions were used for an in-depth analysis of the effects of the transducer's construction on its parameters and values. Based on these findings, a methodology of the design of the transducer was developed. The transducer was designed and built according to the methodology. It was subsequently studied in detail. The results of the study have confirmed that the method of the analysis and the design were correct. Finally, the article presents some examples of real signals of acoustic emission of the temporomandibular joint as they were received by the ultrasonic transducer built in the course of the work.

Studying the acoustic emission of the temporomandibular joint

Lis W., Salomon R., Zienkiewicz J.

Archives of Acoustics

1999

Vol. 24, no. 3

303-318

The method of acoustic emission is widely used for testing the strength of materials and in passive underwater acoustics. Recently in the field of medicine, acoustic emission signals received in the traditional phonendoscope method are recorded and processed using advanced electronic technology. Presented in this paper is an example of this work. It is a system that tests the acoustic emission of the temporomandibular joint which when in a pathological state seriously impairs important physiological functions of man. The presented system receives and records acoustic signals emitted by the joint. This is synchronised with the registration of the jaw displacement. Based on that, parameters and characteristics of acoustic emission signals which could indicate a specific disease of the joint are determined. In the research to date the focus has been on determining the statistical distributions of root-mean-square and maximal values of the signals and the current spectrums linked to the movement of the mandible. Clinical tests carried out at the Clinic of Maxillofacial Surgery at the Medical Academy of Gdańsk have provided preliminary confirmation of the usefulness of the system for diagnostic functions. The tests are being continued and are systematically contributing to the collection of signals and cases. This in turn is the condition of progress of continued work on the use of acoustic emission in diagnosing the temporomandibular joint.