E. N. Goodyer

Measurements of Vocal Fold Elasticity Using the Linear Skin Rheometer

Objective: The linear skin rheometer (LSR), which measures skin visco-elasticity, was adapted for measurements of vocal fold properties. A series of studies was performed on animal and human excised larynges to determine if the LSR technique can be applied to the vocal fold. Methods: In excised larynges, small patches of mucosa were driven sinusoidally at 0.3 Hz over distances of 1–2 mm using a small probe. Forces in the order of 1 g equivalent gave optimal measurements. Stiffness and viscosity values were derived from stress/strain data. Results: The instrument was able to measure the visco-elasticity of the tissue in a repeatable manner and it could detect areas where the tissue was artificially stiffened. Two-dimensional maps of the mechanical properties of the laryngeal mucosa were obtained showing local variations in elasticity both parallel and perpendicular to the vocal fold edge. Initial studies were undertaken using animal tissue; more recently, the LSR has been successfully used to obtain similar data from human tissue. Conclusion: The LSR was been demonstrated to be capable of measuring the elastic properties of the vocal fold in a repeatable and reliable manner. Further studies will now be undertaken to obtain data from a larger sample of human tissue.

In vivo measurement of the elastic properties of the human vocal fold

The ability to measure the biomechanical properties of the vocal fold in vivo is both an aid to diagnosis and enhances our knowledge of how the vocal folds operate. This paper details a new instrument that is capable of taking readings of the spring rate of the vocal fold in a repeatable manner. We also present three sets of readings taken from two volunteer patients. Patient 1 was suffering from polyp growth, and the data presented are taken from both the damaged vocal fold and the healthy vocal fold. The third set of readings was obtained from a similar volunteer and taken from a healthy vocal fold. It can be seen that the data obtained from the healthy vocal folds are similar and that the data obtained from the diseased vocal fold is at variance.

Viscoelastic measurements after vocal fold scarring in rabbits--short-term results after hyaluronan injection.

Abstract Conclusions. The scarring model resulted in significant damage and elevated viscoelasticity of the lamina propria. Hyaluronan preparations may alter viscoelasticity in scarred rabbit vocal folds. Objectives. Vocal fold scarring results in stiffness of the lamina propria and severe voice problems. The aims of this study were to examine the degree of scarring achieved in the experiment and to measure the viscoelastic properties after injection of hyaluronan in rabbit vocal folds. Materials and methods. Twenty-two vocal folds from 15 New Zealand rabbits were scarred, 8 vocal folds were controls. After 8 weeks 12 of the scarred vocal folds received injections with 2 types of cross-linked hyaluronan products and 10 scarred folds were injected with saline. After 11 more weeks the animals were sacrificed. After dissection, 15 vocal folds were frozen for viscoelastic measurements, whereas 14 vocal folds were prepared and stained. Measurements were made of the lamina propria thickness. Viscoelasticity was measured on intact vocal folds with a linear skin rheometer (LSR) adapted to laryngeal measurements. Results. Measurements on the digitized slides showed a thickened lamina propria in the scarred samples as compared with the normal vocal folds (p <0.05). The viscoelastic analysis showed a tendency to stiffening of the scarred vocal folds as compared with the normal controls (p =0.05). There was large variation in stiffness between the two injected hyaluronan products.

Fuzzy data fusion for fault detection in Wireless Sensor Networks

Wireless Sensor Networks (WSN) can produce decisions that are unreliable due to the large inherent uncertainties in the areas which they are deployed. It is vital for the applications where WSNs are deployed that accurate decisions can be made from the data produced. Fault detection is a vital pursuit, however it is a challenging task. In this paper we present a fuzzy logic data fusion approach to fault detection within a Wireless Sensor Network using a Statistical Process Control and a clustered covariance method. Through the use of a fuzzy logic data fusion approach we have introduced a novel technique into this area to reduce uncertainty and false-positives within the fault detection process.

The shear modulus of the human vocal fold in a transverse direction

The aim of this study was to measure the shear modulus of the vocal fold in a human hemilarynx, such that the data can be related to direction of applied stress and anatomical context. Dynamic spring rate data were collected using a modified linear skin rheometer using human hemilarynges, and converted to estimated shear modulus via application of a simple shear model. The measurement probe was attached to the epithelial layer of the vocal fold cover using suction. A sinusoidal force of 3g was applied to the epithelium, and the resultant displacement logged at a rate of 1kHz. Force measurement accuracy was 20microg and position measurement accuracy was 4microm. The force was applied in a transverse direction at the midmembranous point between the vocal process and the anterior commissure. The shear modulus of the three female vocal folds ranged from 814 to 1232Pa. The shear modulus of the three male vocal folds ranged from 1021 to 1796Pa. These data demonstrate that it is possible to obtain estimates for the shear modulus of the vocal fold while preserving anatomical context. The modulus values reported here are higher than those reported using parallel plate rheometry. This is to be expected as the tissue is attached to surrounding structures, and is under natural tension.

In vivo measurement of the shear modulus of the human vocal fold : interim results from eight patients

The shear modulus of the vocal fold is an essential parameter required to enhance our understanding of how the vocal fold operates, to develop mathematical models of phonatation, and to provide benchmarks to quantify the effectiveness of surgical procedures. The authors announced the successful deployment of an instrument to measure vocal fold elasticity in vivo last year, and now present the data taken from eight patients in vivo. The shear modulus was measured at the mid-membranous point, in a transverse direction with respect to the axis drawn between the anterior commissure and vocal process. The range of mean shear modulus results is 701–2,225 Pa, with a mean value of 1,371 Pa.

Control of vocal fold cover stiffness by laryngeal muscles: A preliminary study†

To perform preliminary measurements of the shear modulus of the vocal fold cover layer during intrinsic laryngeal muscle contraction.

GRADATION OF STIFFNESS OF THE MUCOSA INFERIOR TO THE VOCAL FOLD

During phonation, energy is transferred from the subglottal airflow through the air/mucosa interface that results in the propagation of the mucosal wave in the vocal fold. The vocal fold is soft, and the subglottal mucosa is stiff. We hypothesize that it is highly improbable that there is a rigid boundary between the tissue structures, with a sudden drop in stiffness; and that a gradual change would be more likely to support the efficient transfer of energy from the airflow to the mucosal wave. Our objective was to test this hypothesis by quantifying the change in mucosa stiffness with respect to anatomical position. In this initial study, using five pig larynges, a series of point-specific measurements of mucosa stiffness were taken in a line from the midpoint of the vocal fold toward the trachea. A modified linear skin rheometer adapted for laryngeal elasticity measurement applied shear stress to a series of seven positions at 2-mm intervals starting from the midmembranous vocal fold medial surface. A sinusoidal shear force of 1g was applied at each point, and resultant displacement curve logged. Using a regression algorithm, the stiffness of the tissue was derived in units of grams force per millimeter displacement. Five readings were taken at each position. The results indicate that there is a linear increase in stiffness with respect to position, increasing as the measurements are taken further from the vocal fold. There is a gradual change in stiffness of the subglottal mucosa of a pig larynx.

Application of Artificial Neural Network and Support Vector Regression in cognitive radio networks for RF power prediction using compact differential evolution algorithm

Cognitive radio (CR) technology has emerged as a promising solution to many wireless communication problems including spectrum scarcity and underutilization. To enhance the selection of channel with less noise among the white spaces (idle channels), the a priory knowledge of Radio Frequency (RF) power is very important. Computational Intelligence (CI) techniques cans be applied to these scenarios to predict the required RF power in the available channels to achieve optimum Quality of Service (QoS). In this paper, we developed a time domain based optimized Artificial Neural Network (ANN) and Support Vector Regression (SVR) models for the prediction of real world RF power within the GSM 900, Very High Frequency (VHF) and Ultra High Frequency (UHF) FM and TV bands. Sensitivity analysis was used to reduce the input vector of the prediction models. The inputs of the ANN and SVR consist of only time domain data and past RF power without using any RF power related parameters, thus forming a nonlinear time series prediction model. The application of the models produced was found to increase the robustness of CR applications, specifically where the CR had no prior knowledge of the RF power related parameters such as signal to noise ratio, bandwidth and bit error rate. Since CR are embedded communication devices with memory constrain limitation, the models used, implemented a novel and innovative initial weight optimization of the ANNs through the use of compact differential evolutionary (cDE) algorithm variants which are memory efficient. This was found to enhance the accuracy and generalization of the ANN model.

Devices and Methods on Analysis of Biomechanical Properties of Laryngeal Tissue and Substitute Materials

For understanding the phonatory process in human voice production, physical as well as numerical models have been suggested. Material properties within these models are crucial for achieving vocal fold dynamics being close to in vivo human laryngeal dynamics. Hence, different approaches have been suggested to gain insight into human laryngeal tissue, evaluate clinical treatment, as well as to analyze and verify parameters within synthetically built vocal folds. Purpose of Review: The authors want to give an overview of approaches on receiving material parameters being important in voice research. For the different devices and methods being applied for different set-ups, we will present the functionality and applicability. Hence, for future work, this review shall give an indication, what kind of measurement techniques are suitable for the intended study, advantages or disadvantages of the approaches, and what parameters can be