Sensorless Contact Force Evaluation of Bone-conducted Sound Transducer by Electrical Impedance in Limited Frequency Range

et al. 2017

Noninvasive bone-conducted hearing aids require the consistent fitting of transducers for consistent hearing. In this paper, a method of estimating the contact force and amount of hair between a person’s skin and a bone-conducted sound transducer using electrical impedance is proposed. Experiments are conducted with a human surface model consisting of hair, skin, and bone. The estimator is implemented with a three-layered neural network. Ten measurements for 70 conditions are conducted by changing the contact force from 0 to 5 N and the amount of hair from 0 to 169.6 mm3. With the trained estimator, it is possible to estimate contact force and the intermediate material thickness with mean errors of 0.025 N and 0.424 mm3. This result supports the feasibility of the proposed method and contributes to the reproducible placement of the bone-conducted sound transducer.

Section: Human Headmentioning

confidence: 99%

Estimation of contact force and amount of hair between skin and bone-conducted sound transducer using electrical impedance

et al. 2017

“…We propose a method that uses the electrical impedance of the transducer [36][37][38] to solve this problem of contact force estimation. The electrical impedance of the transducer shows a characteristic change according to the contact force.…”

Section: Introductionmentioning

confidence: 99%

“…To solve this problem, we previously proposed a vibration model with two-degrees-of-freedom and verified its characteristics by measuring the electrical impedance. 39) However, the model was verified only with the measured data and has not been applied to the estimation.…”

Section: Introductionmentioning

confidence: 99%

Method of estimating contact force of bone-conducted sound transducer with a two-degrees-of-freedom vibrating model

et al. 2019

In this paper, we propose a method of estimating the contact force of a bone-conducted sound transducer with a two-degrees-of-freedom vibrating model. First, the electrical impedance of the transducer was measured by varying the contact force applied to 12 human subjects. The model was fit to the measurement electrical impedance by changing the damping coefficient. The results showed that the model's damping coefficient is related to the contact force. The fitting was valid when the contact force was below than 3.0 N. Second, a contact force estimation method utilizing the relationship between the damping coefficient and the contact force was proposed. The contact force was estimated by estimating the damping coefficient from the measured impedance and calculating the corresponding contact force from the damping-contact force curve. The estimation results showed that the proposed method achieves reasonable accuracy compared to a previous method using a neural network. Also, the proposed method can be achieved with only two calibration conditions, 0.3 N and 0.5 N, by employing a physical model. This drastically reduces the calibration process compared to the previous methods.

“…If the mechanical impedance changes according to the contact force, it also appears as the electrical impedance. We have validated the relationship between the contact force and the electrical impedance using a human model, 39) and proposed a method of estimating the contact force from the electrical impedance. 40) However, the results were obtained only from the human model, and measurements with human subjects have not been discussed.…”

Section: Introductionmentioning

confidence: 99%

“…A preliminary experiment showed that human subjects show similar trends to the human model. 41) However, the method of estimating the contact force was not proposed with data from human subjects.…”

Section: Introductionmentioning

confidence: 99%

Verification of contact force estimation method for the bone-conducted sound transducer with human subjects

et al. 2018

In this study, we evaluated a method of estimating the contact force of a bone-conducted sound transducer using human subjects. The method was previously proposed and evaluated only with a human model. First, the relationship between the contact force and the electrical impedance was validated for 12 human subjects from 10 Hz to 60 kHz. The results showed that the electrical impedance shows four peaks and that the peaks change with contact force for all subjects in the same manner. A method of estimating the contact force was implemented with a three-layered neural network and evaluated with the data from 12 human subjects. The estimation results showed that 90% of the estimation error was within ±0.43 N, which shows that the estimation of contact force is possible. This result enables the estimation of contact force only from the electrical impedance and may support reproducible fitting of the bone-conducted sound transducer.