Diaphragm Velocity Research Articles

Diaphragm Assessment by Multimodal Ultrasound Imaging in Healthy Subjects.

In recent years, diaphragm ultrasound (DUS) has been used to identify diaphragm dysfunction in the intensive care unit (ICU). However, there are few studies on DUS parameters to evaluate function, normal ranges, and influencing factors in population. The aim of this study is to provide a methodological reference for clinical evaluation of diaphragm function by measuring different DUS parameters in a healthy population. A descriptive study was conducted 212 (105 males, 107 females) subjects with normal spirometry underwent ultrasound imaging in this study. The diaphragm contraction and motion related parameters and shear wave velocity (SWV) were measured in the supine position. The effects of gender, age, body mass index (BMI) and lifestyle on diaphragm ultrasound parameters were analyzed. The diaphragm thickness at end-expiration (DT-exp) was 0.14 ±0.05 cm, the diaphragm thickness at end- inspiration (DT-insp) was 0.29±0.10 cm, with thickening fraction (TF) was 1.11±0.54. The diaphragm excursion (DE) was 1.68±0.37cm and diaphragm velocity was 1.45±0.41 cm/s during calm breathing. During deep breathing, the DE was 5.06±1.40cm and diaphragm velocity was 3.20±1.18 cm/s. The Diaphragm shear modulus-longitudinal view were Mean16.72±4.07kPa, Max25.04±5.58kPa, Min11.06±3.88kPa, SD2.56±0.98. The results of diaphragmatic measurement showed that the DT of males was significantly greater than that of females (P< 0.05), but there was no significant difference in TF. The DT-insp (r=0.155, P= 0.024) and the DT-exp (r=0.252, P=0.000) were positively correlated with age, and the DE during calm breathing was negatively correlated with age (r=-0.218, P= 0.001) and BMI (r=-00.280, P= 0.000). The DE (R=0.371, P=0.000) and velocity (R=0.368, P=0.000) during deep breathing were correlated with lifestyle. Our study provides normal reference values of the diaphragm and evaluates the influence of gender, age, body mass index and lifestyle on diaphragmatic morphology.

Relationship between respiratory muscles ultrasound parameters and running tests performance in adolescent football players. A pilot study.

Assessing the relationship between ultrasound imaging of respiratory muscles during tidal breathing and running tests (endurance and speed) in adolescent football players. Ultrasound parameters of the diaphragm and intercostal muscles (shear modulus, thickness, excursion, and velocity), speed (30-m distance), and endurance parameters (multi-stage 20-m shuttle run test) were measured in 22 male adolescent football players. The relation between ultrasound and running tests were analysed by Spearman's correlation. Diaphragm shear modulus at the end of tidal inspiration was moderately negatively (R=-0.49;p=0.2) correlated with the speed score at 10 m. The diaphragm and intercostal muscle shear modulus ratio was moderately to strongly negatively correlated with the speed score at 10 m and 30 m (about R=-0.48;p=0.03). Diaphragm excursion was positively correlated with the speed score at 5 m (R=0.46;p=0.04) and 10 m (R=0.52;p=0.02). Diaphragm velocity was moderately positively correlated with the speed score at 5 m (R=0.42;p=0.06) and 30 m (R=0.42;p=0.07). Ultrasound parameters were not significantly related to all endurance parameters (R≤0.36;p≥0.11). Ultrasound parameters of the respiratory muscles are related to speed score in adolescent football players. The current state of knowledge does not allow us to clearly define how important the respiratory muscles' ultrasound parameters can be in predicting some performance parameters in adolescent athletes.

Laser-based comparison calibration of laboratory standard microphones.

A precision laser-based comparison calibration method for laboratory standard microphones is described that uses reference microphones calibrated by the pressure reciprocity method. Electrical drive current and diaphragm velocity are measured while the microphones are driven as transmitters/sources of sound; the diaphragm velocity is measured using scanning laser Doppler vibrometry. Sensitivities determined using this method display very good agreement with those determined directly by reciprocity for seven such test microphones at 250 and 1000 Hz. At these frequencies, the expanded (coverage factor k = 2) uncertainties of this comparison calibration method for these microphones are ±0.05 dB.

Laser-based comparison calibration of laboratory standard microphones

A precision laser-based comparison calibration method for laboratory standard microphones is described that uses reference microphones calibrated by the pressure reciprocity method. Electrical drive current and diaphragm velocity are measured while the microphones are driven as transmitters/sources of sound; the diaphragm velocity is measured using scanning laser Doppler vibrometry. Sensitivities determined using this method display very good agreement with those determined directly by reciprocity for seven such test microphones at 250 and 1000 Hz. At these frequencies, the expanded (coverage factor k = 2) uncertainties of this comparison calibration method for these microphones are ±0.05 dB.

Novel experimental research on the compression process in organic Rankine cycle (ORC)

Organic Rankine cycle (ORC) is one of the most promising methods for converting medium-low temperature thermal energy into power. Many studies have been performed to optimize the operating conditions, select proper working fluids, design efficient expansion machines, etc. However, as the major power-consuming component in ORC system, the circulating pump is rarely studied. Most of theoretical studies only assume a constant value of isentropic efficiency for the compression process, but this value varies with different studies. A small-scale ORC system is built in the present work to test the performance of a diaphragm pump, and the working fluids of R245fa, R123, R152a and R600a are tested under various conditions. The isentropic efficiencies of diaphragm pump for compressing those working fluids are between 57.22% and 93.51%. The results show that volume flow rate and pressure difference have great influence on isentropic efficiency, and the isentropic efficiency increases with the volume flow rate and pressure difference. Under the condition of same volume flow rate and pressure difference, the isentropic efficiency conforms to the order of ηR245fa>ηR123>ηR600a>ηR152a. The analyses about the variation trend of isentropic efficiency are made from the perspectives of physical properties of working fluid and the driving mode of diaphragm pump, which prove that the hitting velocity of diaphragm to the liquid is the main cause for irreversible enthalpy increment. A novel parameter αV/ρcp is proposed to identify the influence of physical properties of working fluid on the performance of pump. The experimental results show that under same volume flow rate and pressure difference, the isentropic efficiency of pump decreases with the increment of αV/ρcp of different working fluids.

Numerical and theoretical analysis of sound absorption by an actively controlled electrodynamic loudspeaker

This work addresses the dynamic modeling and simulation of electrodynamic loudspeakers as active acoustic absorbers. A dynamic system is formulated based on the coupling of acoustic and electromechanical phenomena to describe the behavior of a loudspeaker placed at the end of a straight duct. Next, a proportional-plus-derivative feedback control system combined with a feedforward structure is developed to allow the loudspeaker to perform active impedance control. In contrast to previous works, the proposed control strategy relies on measurements of the electric current rather than of the diaphragm velocity. Computational simulations show that the control system is stable, reliable and efficient in increasing the acoustic absorption in a large frequency range, even though some limitations due to the loudspeaker operation may exist.

모바일 폰용 마이크로스피커의 음향 및 전기 해석

In this paper, GUI program for microspeaker system simulation program was developed and verified through closed box, vent box and 6th order bandpass enclosure system. By using the pseudo loudspeaker model concept, TS parameters and rear volume of microspeaker were identified. Their suitabilities were proved by comparing test results with simulations of electrical impedance and sound pressure response curves for the three box types; closed box, vent box and 6th order bandpass box. Also, MSSP was found to be effective regardless of the microspeaker's shape, either circular or rectangular shape. MSSP can be used for the microspeaker system simulation, and can give a general prediction of such as; sound pressure level curve, electrical impedance, diaphragm velocity and displacement curve according to multiple design parameters; diaphragm mass, compliance, force factor, front and rear volume, front and rear port's diameter and length.

Two-port network analysis and modeling of a balanced armature receiver

Models for acoustic transducers, such as loudspeakers, mastoid bone-drivers, hearing-aid receivers, etc., are critical elements in many acoustic applications. Acoustic transducers employ two-port models to convert between acoustic and electromagnetic signals. This study analyzes a widely-used commercial hearing-aid receiver ED series, manufactured by Knowles Electronics, Inc. Electromagnetic transducer modeling must consider two key elements: a semi-inductor and a gyrator. The semi-inductor accounts for electromagnetic eddy-currents, the ‘skin effect’ of a conductor (Vanderkooy, 1989), while the gyrator (McMillan, 1946; Tellegen, 1948) accounts for the anti-reciprocity characteristic [Lenz's law (Hunt, 1954, p. 113)]. Aside from Hunt (1954), no publications we know of have included the gyrator element in their electromagnetic transducer models. The most prevalent method of transducer modeling evokes the mobility method, an ideal transformer instead of a gyrator followed by the dual of the mechanical circuit (Beranek, 1954). The mobility approach greatly complicates the analysis. The present study proposes a novel, simplified and rigorous receiver model. Hunt's two-port parameters, the electrical impedance Ze(s), acoustic impedance Za(s) and electro-acoustic transduction coefficient Ta(s), are calculated using ABCD and impedance matrix methods (Van Valkenburg, 1964). The results from electrical input impedance measurements Zin(s), which vary with given acoustical loads, are used in the calculation (Weece and Allen, 2010). The hearing-aid receiver transducer model is designed based on energy transformation flow [electric→ mechanic→ acoustic]. The model has been verified with electrical input impedance, diaphragm velocity in vacuo, and output pressure measurements.This receiver model is suitable for designing most electromagnetic transducers and it can ultimately improve the design of hearing-aid devices by providing a simplified yet accurate, physically motivated analysis.This article is part of a Special Issue entitled “MEMRO 2012”.

A piezoelectric microelectromechanical systems ultrasonic radiator.

The development of a piezoelectric micromachined ultrasonic radiator is presented. The transmitter is formed by a radially non‐uniform circular composite diaphragm. The diaphragm consists of a layer of piezoelectric material with annular electrodes. Transduction of the diaphragm occurs when an electric field is induced between annular electrodes across the piezoelectric material creating mechanical strain in the annular region. The strain couples into force and moment resultants that generate diaphragm deflection. A time varying electric field induces vibrations of the diaphragm which in turn generates acoustic waves. Included in the overall systems design of the transmitter is a unique package with back cavity depth control. A systems model incorporates electrical, mechanical, and acoustic components using composite plate mechanics, lumped element modeling, and acoustic theory. Comparison to experimental results is conducted through mechanical and acoustic characterizations. A laser vibrometer system measures diaphragm velocity from which the fundamental mode shape and resonant frequency are extracted. Farfield acoustic measurements are compared to the extrapolation of vibrometer measurements via Rayleigh’s integral. The characterization results show mismatch between devices as well as the equivalent circuit model. Experimental results of the variable back cavity depth show a qualitative match to the systems model.

Interior noise control through tuned loudspeaker absorption

In this work we describe the development and application of an interior noise control approach based on active loudspeaker tuning for sound absorption. Loudspeakers are tuned to minimize global sound pressure at specific acoustic modes through diaphragm velocity feedback. An experimental model of the acoustic space used for controller design is obtained through system identification. H2 optimal controllers are designed to minimize a performance microphone output by feeding back the tuned loudspeaker diaphragm velocity. By sensing speaker velocity rather than far-field sound pressure, the loudspeaker is actively tuned to minimize reflected sound at specific acoustic modes and therefore reduce the global pressure field. Experimental results, obtained from an acoustic enclosure modeled after a rocket fairing, are used to demonstrate the effectiveness of the tuned loudspeaker at global attenuation. Details of the design procedure and experimental applications are discussed.

Optimization of micro-loudspeaker radiation via finite element modeling

Measurements and predictions from numerical models for the response of and radiation from a micro-loudspeaker are compared. The numerical models are then used to examine various means for improving the performance of the loudspeaker radiation by varying the material properties of the loudspeaker. A commercial finite element code uses measured material properties to predict the diaphragm velocity distribution of lower order modes. Noncontact laser vibrometer measurements on the excited speaker are compared with the FEM predictions. The radiation from the loudspeaker, at frequencies of resonance, is predicted by a boundary element model. Diaphragm material properties (density, thickness, and elastic modulus) were varied and the sensitivity of the radiation to the material properties of the diaphragm determined.

Velocity Estimator Based Compensation for Loudspeakers

Loudspeakers are mechatronic devices that are commonly used as actuators in active noise control applications. Unfortunately they can add significantly to the dynamics of the control loop and therefore be detrimental to control performance. In this work motional feedback is used to compensate the loudspeaker so that its dynamics better approximate a constant velocity source. A novel approach of using a velocity estimator to provide a measurement of the diaphragm velocity is used. The estimator is determined using a frequency domain identification technique.

Automated monitoring of diaphragm end-expiratory position for real-time navigator echo MR coronary angiography

Real-time navigator echo (NE)-gated magnetic resonance coronary angiography (MRCA) during free respiration is now possible. However, the mean diaphragm end-expiratory position (DEEP) drifts over time, and this results in a reduction in scanning efficiency and increased artifacts due to the acquisition of data during periods of high diaphragm velocity. To address these problems, a diaphragm monitoring program that follows the mean DEEP over time has been developed. Fifteen subjects with ischemic heart disease underwent continuous NE monitoring of their diaphragm for 30 minutes. Using these diaphragm traces, theoretical MRCA scans were performed. Several diaphragm monitoring algorithms were developed and compared with the simplest case (a stationary 5 mm NE acceptance window placed around the mean DEEP, as measured by NE monitoring at the outset of the scan). An overall scan efficiency was calculated, and the number of completed scans where the mean DEEP lay within the NE acceptance window was recorded. Of the six algorithms considered, the most effective one monitored the mean DEEP and prospectively placed the upper limit of the NE acceptance window on this position for the subsequent acquisition. Using this algorithm in comparison with the simplest stationary scenario, both scan efficiency (47.9% vs. 38.5%, P = 0.01) and the number of completed scans where the mean DEEP lay within the NE acceptance window (71.2 vs. 30.3, P < 0.001) were improved. The implementation of such a monitoring algorithm, in combination with adaptive motion correction techniques, should improve overall scan efficiency while maintaining the end-expiratory position at the top end of the NE acceptance window, to reduce image artifacts.

Sound reproduction system

A sound system for reproducing the full frequency spectrum of recorded sound throughout a listening environment at its natural volume and in the same spatial relationships as the originally created sound includes a multidirectional main audio driver utilizing the convex area of a conical shell diaphragm integrated with an acoustically reflective throating inertial regulator disk to provide spatial acoustic coupling between the audio driver and the atmosphere that approximates a live performance. The regulator disk is a rigid reflective plate mounted in a plane which forms an interior angle between 45* and 75* with the axis of the conic diaphragm. The plate may be flat, or shaped hyperbolically or exponentially. It may be either integral with the conical diaphragm assembly or separate and attached by external means. A bass equalization device comprising a tube of controlled inertance having an acoustically resistive network inserted therein amplifies the output from the convex radiating surface of the audio driver and equalizes the bass and upper frequency audio power output. It also serves to cancel the outof-phase upper frequency sound waves generated by the concave radiating surface. The bass equalization device and the inertance regulator disk control the resonant frequency and inertance of the system. The bass frequency output faces a cabinet enclosure equalized without resonance so that 12 through 512 Hz. is generated without spurious harmonic partials or parasitic frequency components. Horizontal-radial and vertical dispersion speakers, comprising high frequency response speakers, are vertically oriented and face a conic, hyperbolic or exponential throating and inertance regulated dispersion surface for a full spatial distribution of the upper frequency audio output. The sound reproduction system may further be described as an inertially regulated sonic transducer. By controlling the diaphragm velocity and acoustic expansion rate audio reproduction can be recreated that approximates the spatial perspective of a live performance.

Respiratory changes in thoracic muscle length during bronchoconstriction.

The purpose of the present study was to assess the effects of bronchoconstriction on respiratory changes in length of the costal diaphragm and the parasternal intercostal muscles. Ten dogs were anesthetized with pentobarbital sodium and tracheostomized. Respiratory changes in muscle length were measured using sonomicrometry, and electromyograms were recorded with bipolar fine-wire electrodes. Administration of histamine aerosols increased pulmonary resistance from 6.4 to 14.5 cmH2O X l-1 X s, caused reductions in inspiratory and expiratory times, and decreased tidal volume. The peak and rate of rise of respiratory muscle electromyogram (EMG) activity increased significantly after histamine administration. Despite these increases, bronchoconstriction reduced diaphragm inspiratory shortening in 9 of 10 dogs and reduced intercostal muscle inspiratory shortening in 7 of 10 animals. The decreases in respiratory muscle tidal shortening were less than the reductions in tidal volume. The mean velocity of diaphragm and intercostal muscle inspiratory shortening increased after histamine administration but to a smaller extent than the rate of rise of EMG activity. This resulted in significant reductions in the ratio of respiratory muscle velocity of shortening to the rate of rise of EMG activity after bronchoconstriction for both the costal diaphragm and the parasternal intercostal muscles. Bronchoconstriction changed muscle end-expiratory length in most animals, but for the group of animals this was statistically significant only for the diaphragm. These results suggest that impairments of diaphragm and parasternal intercostal inspiratory shortening occur after bronchoconstriction; the mechanisms involved include an increased load, a shortening of inspiratory time, and for the diaphragm possibly a reduction in resting length.