“…The results for the sensor element (Figure 8) can be confirmed by former investigations [15,16]. These previous studies were conducted on a sensor element of the same size as the whole transducer examined here.…”
Section: Discussionsupporting
confidence: 89%
“…Previous studies have also revealed additional contact points in seven out of ten temporal bones. The impact on sensor output was found to be quite low (about 5 dB) [16]. The effect on the transducer sensor is expected to be on a similar scale.…”
Implantable assembly components that are biocompatible and highly miniaturized are an important objective for hearing aid development. We introduce a mechanical transducer, which could be suitable as part of a prospective fully-implantable hearing aid. The transducer comprises a sensor and an actuator unit in one housing, located in the joint gap between the middle ear ossicles, the incus and stapes. The setup offers the advantage of a minimally invasive and reversible surgical solution. However, feedback between actuator and sensor due to mechanical coupling limits the available stable gain. We show that the system can be stabilized by digital control algorithms. The transducer is tested both in a finite elements method simulation of the middle ear and a physical model of a human middle ear. First, we characterize the sensor and actuator elements separately. Then, the maximum stable gain (MSG) of the whole transducer is experimentally determined in the middle ear model. With digital feedback control (using a least mean squares algorithm) in place, the total signal gain is greater than 30 dB for frequencies of 1 kHz and above. This shows the potential of the transducer as a high frequency hearing aid.
“…The results for the sensor element (Figure 8) can be confirmed by former investigations [15,16]. These previous studies were conducted on a sensor element of the same size as the whole transducer examined here.…”
Section: Discussionsupporting
confidence: 89%
“…Previous studies have also revealed additional contact points in seven out of ten temporal bones. The impact on sensor output was found to be quite low (about 5 dB) [16]. The effect on the transducer sensor is expected to be on a similar scale.…”
Implantable assembly components that are biocompatible and highly miniaturized are an important objective for hearing aid development. We introduce a mechanical transducer, which could be suitable as part of a prospective fully-implantable hearing aid. The transducer comprises a sensor and an actuator unit in one housing, located in the joint gap between the middle ear ossicles, the incus and stapes. The setup offers the advantage of a minimally invasive and reversible surgical solution. However, feedback between actuator and sensor due to mechanical coupling limits the available stable gain. We show that the system can be stabilized by digital control algorithms. The transducer is tested both in a finite elements method simulation of the middle ear and a physical model of a human middle ear. First, we characterize the sensor and actuator elements separately. Then, the maximum stable gain (MSG) of the whole transducer is experimentally determined in the middle ear model. With digital feedback control (using a least mean squares algorithm) in place, the total signal gain is greater than 30 dB for frequencies of 1 kHz and above. This shows the potential of the transducer as a high frequency hearing aid.
“…Another type of a piezoelectric force transducer (H3) was presented by Koch et al in 2013 [ 55 ]. The study proposed a bidirectional membrane transducer, to be inserted at the incudostapedial joint (Fig 8 b) and to sense the force transmitted through this joint.…”
Section: Description Of Implantable Sensorsmentioning
confidence: 99%
“… Fig. 10 Frequency responses sensitivity frequency responses of a the subcutaneous microphones A1 [ 9 ] and A2 [ 10 ] under patients’ skin, microphone A4 in a free field and under the skin [ 50 ]; b the electromagnetic sensor B [ 51 ] in human TBs (malleus), the capacitive microphone G in guinea pigs (ME cavity) [ 12 ], the piezoelectric force transducers H1 in cats (incus) [ 14 ] and H3 in a synthetic ossicular chain (incudostapedial joint) [ 55 ], the piezoelectric accelerometer I in TBs (incus) [ 73 ]; c the piezoresistive MEMS accelerometer D (incus) [ 16 ], the capacitive MEMS displacement sensors E1 [ 22 ] and E2 [ 20 ] in human TBS (umbo), the capacitive MEMS accelerometers F1 [ 21 ] and F2 [ 23 ] in human TBs (umbo), and the piezoelectric MEMS accelerometer J2 [ 18 ] in human TBs (umbo) …”
Section: Sensor Performance Comparisonmentioning
confidence: 99%
“… Fig. 11 Equivalent input noise (EIN) equivalent input noise of a the capacitive microphone G in guinea pigs (ME cavity) [ 12 ], the piezoelectric force transducers H3 in a synthetic ossicular chain (incudostapedial joint) [ 55 ], the piezoelectric accelerometer I in TBs (incus) [ 73 ]; b the piezoresistive MEMS accelerometer D (incus) [ 16 ], the capacitive MEMS displacement sensors E1 [ 22 ] and E2 [ 20 ] in human TBS (umbo), the capacitive MEMS accelerometers F1 [ 21 ] and F2 [ 23 ] in human TBs (umbo), and the piezoelectric MEMS accelerometer J2 [ 18 ] in human TBs (umbo). Both figures include the EIN of ECM used in conventional HAs [ 7 ] …”
Most commercially available cochlear implants and hearing aids use microphones as sensors for capturing the external sound field. These microphones are in general located in an external element, which is also responsible for processing the sound signal. However, the presence of the external element is the cause of several problems such as discomfort, impossibility of being used during physical activities and sleeping, and social stigma. These limitations have driven studies with the goal of developing totally implantable hearing devices, and the design of an implantable sensor has been one of the main challenges to be overcome. Different designs of implantable sensors can be found in the literature and in some commercial implantable hearing aids, including different transduction mechanisms (capacitive, piezoelectric, electromagnetic, etc), configurations microphones, accelerometers, force sensor, etc) and locations (subcutaneous or middle ear). In this work, a detailed technical review of such designs is presented and a general classification is proposed. The technical characteristics of each sensors are presented and discussed in view of the main requirements for an implantable sensor for hearing devices, including sensitivity, internal noise, frequency bandwidth and energy consumption. The feasibility of implantation of each sensor is also evaluated and compared.
A fully implantable hearing aid is introduced which is a combined sensor-actuator-transducer designed for insertion into the incudostapedial joint gap (ISJ). The active elements each consist of a thin titanium membrane with an applied piezoelectric single crystal. The effectiveness of the operating principle is verified in a temporal bone study. We also take a closer look at the influence of an implantation-induced increase in middle ear stiffness on the transducer's output. An assembly of the transducer with 1 mm thickness is built and inserted into six temporal bones. At this thickness, the stiffness of the annular ligament is considerably increased, which leads to a loss in functional gain for the transducer. It is assumed that a thinner transducer would reduce this effect. In order to examine the performance for a prospective reduced pretension, we increased the gap size at the ISJ by 0.5 mm by removing the capitulum of the stapes in four temporal bones. The TM is stimulated with a broadband multisine sound signal in the audiological frequency range. The movement of the stapes footplate is measured with a laser Doppler vibrometer. The sensor signal is digitally processed and the amplified signal drives the actuator. The resulting feedback is minimized by an active noise control least mean square (LMS) algorithm which is implemented on a field programmable gate array. The dynamic range and the functional gain of the transducer in the temporal bones are determined. The results are compared to measurements from temporal bones without ISJ extension and to the results of Finite Elements Model (FE model) simulations. In the frequency range above 2 kHz a functional gain of 30 dB and more is achieved. This proposes the transducer as a potential treatment for high frequency hearing loss, e.g. for patients with noise-induced hearing loss. The transducer offers sufficient results for a comprehensive application. Adaptations in the transducer design or surgical approach are necessary to cope with ligament stiffening issues. These cause insufficient performance for low frequencies under 1 kHz.
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