Surgery – Diagnostic testing – Ear or testing by auditory stimulus
Reexamination Certificate
2001-08-27
2003-12-16
Hindenburg, Max F. (Department: 3736)
Surgery
Diagnostic testing
Ear or testing by auditory stimulus
C600S025000, C600S587000
Reexamination Certificate
active
06663575
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a device for electromechanical stimulation and testing of hearing, comprising an electromechanical transducer for producing mechanical vibrations, and means for non-invasively transmitting the mechanical stimulation vibrations from the electromechanical transducer through the external auditory canal to at least approximately the center of the tympanic membrane (the umbo) and thus to the manubrium mallei of the ossicular chain.
2. Description of Related Art
Generally the audition of a person is tested in that a sound signal and thus an acoustical wave is presented to the test person in a monaural or binaural manner, and that the test person subjectively reacts on proper questions which are adequate to the respective purpose of the psychoacoustical test. Such electroacoustical devices are generally termed “audiometer”, and in most applications the test signal either is generated electronically (by analog or digital signal generators) or is derived from a suitable sound carrier (magnetic tape, compact disc and the like). These test signals then are acoustically presented to the test person, most frequently by loudspeakers under so-called called “free-field” conditions, or by specifically calibrated measuring earphones. In particular cases, for example when an acoustically sealed volume in front of the tympanic membrane is required for the specific test, these acoustical signals are transmitted to the external auditory canal by short sound-conducting hoses and ear pieces.
Furthermore, objective hearing test methods are known (for example BERA: “Brainstem Evoked Response Audiometry”) in which acoustically evoked neuronal responses are picked up by skin electrodes and are correspondingly analyzed. Besides, the mobility of the middle ear is routinely determined by a method in which the middle ear is deflected by a pressure buildup within the external auditory canal, whilst one or more test tones are supplied by loudspeakers via transmission hoses, and in which pressure and velocity within the external auditory canal are measured by corresponding transducers (microphones and pressure meters). With the aid of these values, the acoustical impedance and changes thereof caused by pathological changes of the middle ear can be determined. The ability of triggering the stapedius reflex likewise can be measured when properly selecting the configuration of the envelope curve and the level.
In all these methods an acoustical signal is presented which, in a known manner, causes the tympanic membrane to mechanically oscillate, wherein these oscillations are transmitted via the ossicular chain of the middle ear to the inner ear and are converted there into a neuronal stimulation pattern which causes an auditory impression.
Furthermore, laser-audiometrical test devices are known (U.S. Pat. No. 6,007,494) in which dynamic movements of the tympanic membrane and of the manubrium mallei of the ossicular chain, respectively, can be optically, and thus in contactless manner, measured by a laser Doppler vibrometer even in the case of very small motion amplitudes near the auditory threshold in quiet.
In addition there are approaches to carry out examinations of the middle ear by direct contact with an electromechanical transducer (DE-A-31 21 429 and A. Thullen: “Klinische Erfahrungen mit der Schallsonde nach Zöllner”, Medizinal-Markt, No. 12, 1956, pp. 444 to 445). In this case a sound probe is contacted with the middle ear, particularly invasively during middle ear operations. A device for pre-operative demonstration for implantable hearing systems and for psychoacoustical measurement of the auditory threshold in quiet by direct mechanical stimulation of the umbo is known from U.S. Pat. No. 5,833,626. This device comprises an electromechanical transducer for generating mechanical vibrations in the audio range, and a rigid mechanical coupling member for transmitting the mechanical vibrations, without surgery, through the external auditory canal in direct mechanical contact to the center of the tympanic membrane and thus to the manubrium mallei of the ossicular chain of the middle ear. Systems for non-invasively coupling such a device to the extra-corporal side of the tympanic membrane are described in U.S. Pat. No. 5,776,144.
German Patent No. 19 821 602 discloses a vibration measuring head comprising an electromechanical transducer, which head permits, exclusively in resonance operation, an evaluation of the movability of the vibratorily movable elements of the middle ear structure coupled to the actoric side of the transducer by means of a second measuring coil because the dampening of the system by the middle ear structure coupled thereto is represented by a variation of the voltage generated by this coil.
Especially in the described objective hearing testing methods (for example, BERA) there are, however, some disadvantages in the type of acoustic excitation, such as for example the magnetic fields generated by the usually used electrodynamic or electromagnetic headphones. These magnetic (interference) fields lead to problems in pre-processing and analysis of the evoked potentials which are electrically derived from the skin surface of the head and which can be in the nV range. For acoustic signals monaurally presented supraliminally at medium to high sound levels the problem of “overhearing” of the contralateral ear, which is not being tested, due to the acoustic sound emission of the headphone or by body sound (bone conduction) continues to occur, which leads to the necessity of acoustic masking of the contralateral ear. This effect is undesirable in many psychoacoustic situations, but inevitable. A disadvantage in using the device known from German Patent No. 198 21 602 particularly is that a broad-band measurement is impossible because the method applied is based on resonance effects of the transducer. Thus a true determination of the mechanical impedance of the middle ear structure coupled to the device is not possible, particularly when measurements in different spectral regions are desired. However, measurements in different spectral regions, at least within the main speech frequency range, are of substantial importance when precise information about the pathological condition of the middle ear or even of the inner ear, which is mechanically coupled thereto, is to be obtained.
SUMMARY OF THE INVENTION
A primary object of the present invention is to provide for a device for electromechanical stimulation and testing of hearing which permits in a particularly reliable manner a non-invasive objective testing of a person's auditory capacity.
According to the invention, this object basically is achieved by a device for electromechanical stimulation and testing of hearing, comprising an electromechanical transducer for producing mechanical stimulation vibrations; means for non-invasively transmitting the mechanical stimulation vibrations from the electromechanical transducer through the external auditory canal to at least approximately the center of the tympanic membrane (the umbo) and thus to the manubrium mallei of the ossicular chain; and an impedance measuring system for measuring the mechanical impedance of a biological load structure which is coupled to the transducer.
The presently used electromechanical transducer basically may be designed in conformity with any known transducer principle. Thus, this transducer particularly may be an electromagnetic, electrodynamic, magnetostrictive, dielectric and particularly piezoelectric transducer.
In conformity with one embodiment of the invention, the impedance measuring system may comprise means for measuring the electrical input impedance of the electromechanical transducer which is coupled to the biological load structure. The data for magnitude and phase of this electrical input impedance reflect the load components coupled to the device because these load components, transformed via the electromechanical coupling of the transducer, appear on the electrical side and
Foreman Jonathan
Hindenburg Max F.
Nixon & Peabody LLP
Phonak AG
Safran David S.
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