The acoustical and perceptual features of snore-related sounds in patients with obstructive sleep apnea sleeping with the dynamic mandibular advancement system MATRx plus®

Purpose: The effect of snoring on the bed partner can be studied through the evaluation of in situ sound records by the bed partner or unspecialized raters as a proxy of real-life snoring perception. The aim was to characterize perceptual snore events through acoustical features in patients with obstructive sleep apnea (OSA) with an advanced mandibular position. Methods: Thirty-minute sound samples of 29 patients with OSA were retrieved from overnight, in-home recordings of a study to validate the MATRx plus® dynamic mandibular advancement system. Three unspecialized raters identified sound events and classified them as noise, snore, or breathing. The raters provided ratings for classification certainty and annoyance. Data were analyzed with respect to respiratory phases, and annoyance. Results: When subdividing perceptual events based on respiratory phase, the logarithm-transformed Mean Power, Spectral Centroid, and Snore Factor differed significantly between event types, although not substantially for the spectral centroid. The variability within event type was high and distributions suggested the presence of subpopulations. The general linear model (GLM) showed a significant patient effect. Inspiration segments occurred in 65% of snore events, expiration segments in 54%. The annoyance correlated with the logarithm of mean power (r = 0.48) and the Snore Factor (0.46). Conclusion: Perceptual sound events identified by non-experts contain a non-negligible mixture of expiration and inspiration phases making the characterization through acoustical features complex. The present study reveals that subpopulations may exist, and patient-specific features need to be introduced

Perceptual snoring as a basis for a psychoacoustical modeling and clinical patient profiling

Purpose The perceptual burden and social nuisance for mainly the co-sleeper can affect the relationship between snorer and bedpartner. Mandibular advancement devices (MAD) are commonly recommended to treat sleep-related breathing such as snoring or sleep apnea. There is no consensus about the definition of snoring particularly with MAD, which is essential for assessing the effectiveness of treatment. We aimed to stablish a notion of perceptual snoring with MAD in place. Methods Sound samples, each 30 min long, were recorded during in-home, overnight, automatic mandibular repositioning titration studies in a population of 29 patients with obstructive sleep apnea syndrome (OSAS) from a clinical trial carried out to validate the MATRx plus. Three unspecialized and calibrated raters identified sound events and classified them as noise, snore, or breathing as well as providing scores for classification certainty and annoyance. Data were analyzed with respect to expiration-inspiration, duration, annoyance, and classification certainty. Results A Fleiss' kappa (>0.80) and correlation duration of events (>0.90) between raters were observed. Prevalence of all breath sounds: snore 55.6% (N = 6398), breathing sounds 31.7% (N = 3652), and noise 9.3% (N = 1072). Inspiration occurs in 88.3% of events, 96.8% contained at least on expiration phase. Snore and breath events had similar duration, respectively 2.58s (sd 1.43) and 2.41s (sd 1.22). Annoyance is lowest for breathing events (8.00 sd 0.98) and highest for snore events (4.90 sd 1.92) on a VAS from zero to ten. Conclusion Perceptual sound events can be a basis for analysis in a psychosocial context. Perceived snoring occurs during both expiration as well as inspiration. Substantial amount of snoring remains despite repositioning of the mandible aimed at the reduction of AHI-ODI

Nonlinear Constitutive Modeling of Piezoelectric Materials

The well-known piezoelectric constitutive equations are applicable to piezoceramics driven by low to moderate fields and therefore representing linear behavior. However, these materials are also known for their ferroelectric and ferroelastic nonlinearities particularly when input fields exceed coercive strength. Such nonlinearities are caused mainly by micro-structural changes in the material known as domain switching. Therefore, a constitutive model that can accommodate the domain switching process can help capture the nonlinear behavior of the material. The past two decades have seen increasingly intensive activities in the attempt to build constitutive models to describe the piezoceramics nonlinearities. One of such models takes the advantage of existing linear constitutive equations. By decomposing the state variables into linear and internal components, the existing piezoelectric constitutive equations are augmented to include internal variables in describing the linear behavior while additional attention is devoted to dealing with the internal states pertinent to material's nonlinearities. The latter requires the modeling of the domain switching process. Together, the augmented linear constitutive equations and a domain switching model provide a complete nonlinear constitutive description. Although very successful in qualitatively capturing the polarization hysteresis and strain butterfly phenomena, a major shortcoming of this approach has been that it cannot match quantitatively with experimental data. The objective of this research is to establish a constitutive model for piezoceramics that can not only qualitatively capture the material's nonlinear behavior over a large loading range, but also quantitatively match key characteristics from experimental data. In doing so, we have made three major contributions: 1) we discovered a flaw in the augmentation of linear constitutive equations for the use of materials in nonlinear regime and proposed a correct form of augmentation; 2) we proposed new domain switching rules based on the observations from single crystal experimental data; and 3) in the pursuit of model accuracy with quantitative description, we proposed the use of creep experiments to capture key characteristics related to time-dependent and rate-dependent responses. A finite element approach is taken to carry out numerical modeling at the microscopic level. Experimental data available in literature have been used to help with model development and validation