Tube Impedance Research Articles

Analisis Daya Serap Suara Material Berbasis Polyester Staple Fibre Untuk Karpet Lantai Kendaraan

This research studies about the ability of the acoustic properties or absorption of the vehicle floor carpet material which consists of several forming components, with an experimental method using the tube impedance method. The components of this car floor carpet material consist of a skin section which includes a surface made of polyester staple fiber plastic fiber, binders made of latex SBR material, backing made of Polyethylene (PE) powder and the under layer made of Polyester Fiber material (PET) Silencer. The carpet material for the vehicle floor was made into three samples to determine the average of sound absorption coefficient. The sound absorption coefficient was obtained from testing the flat test sample using the ASTM E1050-98 tube impedance method. The use of Polyethylene (PE) powder as a backing for floor mats has a sound absorption coefficient with a rating of B (above 0.8) at a frequency of 3,000 Hz. While the sound absorption coefficient reaches the highest point of 0.99 at a frequency of 3,000 Hz. This is because the backing with Polyethylene (PE) powder material has porous holes. The micro surface is used as a layer of air space so that it can effectively reduce and increase the absorption of sound that occurs inside the vehicle when driving. The sound absorption coefficient of vehicle floor carpet increases significantly at low frequencies and slightly decreases at high frequencies

Effect of The Volume of Banana Fiber As A Polymer Composite Amplifier With Polyester Resin Matrix On The Sound Absorption of Acoustic Materials

Research has been carried out on the banana fiber effect as a polymer composite amplifier with polyester resin matrix on the sound absorption of acoustic materials. Sound Absorber material is made with a variation in the volume of banana fiber that is different from polyester resin. The volume of banana fiber and polyester resin used is 15% Fiber: 85% Polyester Resin, 20% Fiber: 80% Polyester Resin, 25% Fiber: 25% Fiber: 75% Resin Polyester, 30% Fiber: 70% Polyester Resin, 35% Fiber: 65% Polyester Resin. So when made composite then the amount of banana fiber used and polyester resin is 100%. Research methods are carried out in the collection of banana fiber, composite manufacturing and testing of sound absorption properties using impedance tubes. The testing of coefficient sound reflection and also sound absorbance coefficient testing is done using sound level meter and signal generator by reference to principle the method of tube impedance via approach to the acoustic box. The banana fiber composite result and polyester resin are able to reflect the sound of highest which is 0.44 in a frequency 500 Hz with fiber 15%. While lowest sound reflection coefficient is 0.06 at a frequency of 8000 Hz and fiber 35%. While in the test the highest value absorbance coefficient that absorbs sound is = 0.94 at fiber volume 35%, and frequency 8000 Hz, while the lowest sound coefficient is 0.56 in fiber 15% and frequency 500 HZ

An improved lumped parameter model predicting attenuation of earmuff with air leakage

Since air leakage is inevitable when earmuffs are worn improperly or together with safety glasses in factory or military, it is required to be considered to accurately predict earmuff attenuation. Besides unwanted air leakage, under controlled air leakage is introduced to earmuff to achieve adjustable attenuations in different signal-to-noise ratios (SNRs) and balance between attenuation and speech intelligibility. This work is to develop an improved lumped parameter model (LPM) to predict earmuff attenuation with consideration of air leakage. Air leakage paths are introduced into conventional LPM without air leakage, and air leakage path impedance is analytically described by Maa’s microperforated tube impedance. Earmuff passive attenuation behavior can be analytically described and analyzed with the improved LPM. Finally, the validity of improved LPM is verified experimentally. The results indicate that the improved LPM can predict earmuff attenuation with air leakage, and air leakage deteriorates earmuff attenuation and turns resonance frequency higher.

PENENTUAN KOEFISIEN SERAP BUNYI PAPAN PARTIKEL DARI LIMBAH PELEPAH KELAPA SAWIT

The study is done to determine the characteristics of the material absorbs the particle board made of palm oil to the midrib 0,6 0,4 density and 0,9 gr / cm3 adhesive with variations 15% and 20 % adhesive urea and formaldehyde in use . Frequencies used is 125,250,500,1000 , and 1200 hz . Value the absorption of sample made showing the price qualified according to sample ISO 11654 to classify it as a silencer and included in a category class the quality c. Research aims to understand characteristic of the coefficients employ the board particles of material midrib palm. Employ procedure test the were based on standard ASTM E1050-98 using the of tube impedance 2 microphone .Sample of measuring diameter ± 99 mm. value density large frequency ( hz ) good affect on value the coefficients employ the ( α ) . Employ a value the will decrease in frequency 1000-1200hz and in density gr 0,9 / cm3.

CFD investigation on the characteristics of annular pulse tube

Abstract CFD models are used to study the performance of circular and annular pulse tubes working at 77–300 K. The oscillating flow and heat transfer characteristics are investigated. In terms of pulse tube impedance, simulation results indicate that the annular shape has negligible influence when the length and flow area are kept the same as circular pulse tube. However, compared with the circular pulse tube, the thermal performance of annular pulse tube apparently deteriorates which is mainly due to the increased thermal losses caused by heat transfer between the internal gas and two cylindrical tube walls (instead of one in the case of circular pulse tube). The expansion efficiency (defined as the enthalpy flow divided by acoustic power at the cold end) of annular pulse tube is lower by about 14% compared with that of circular pulse tube. Among the influencing factors, hydraulic diameter of annular pulse tube has a significant influence on the performance, and smaller hydraulic diameter leads to a reduced expansion efficiency. The effects of tube wall thermal conductivity are also discussed. This study provides a better understanding on the mechanism of annular pulse tube which sets the basis for optimizing a compact low temperature cryocooler for future applications.

Determination Of Acoustic Properties Of Rice Bran Composites A Material Handler Noise

The examination of the acoustic characteristic of rice bran has been performed. The materials are the alternative materials of the noise controllerfrom the use of synthetic fiber materials like glasswool. The examination is completed by using tube impedance method. The result of the examination reveals that the natural fiber materials that have been mixed with glue have a good value of sound absorption at frequency 400-1200 Hz whereas at frequency 200 Hz, its value does not change significantly. The high value of the sound absorption is owned by materials with the bigger porous. Beside the coefficient of the absorbtion, the examination of value of acoustic impendence is also performed. The result shows that the similar composition between natural fiber and glue has a bigger value of impendence compared to the lower composition of glue. It is caused by the fulfillment of the bigger amount of the porous by glue.

Effect of Vermiculite and Bulk Density in the PU Foam Composite Board for the Absorption Coefficient and Acoustic Impedance

This article presents a comprehensive investigation in the acoustic characteristics of flame-retardant PET mesh composite fabric and PU foam with the various bulk density of foam and weight ratio of vermiculite. By using impedance tube, absorption coefficients and acoustic impedance of composite material which play an important roles in the estimation of the wave propagation passing through the specific material will be obtained. Results showed that foam with higher bulk density not only increased the material characteristics in the absorption but more importantly, cause the wider band for absorption. With the inclusion of vermiculites, the level of absorption of composite material will obviously increase, especially for the higher frequencies. Instead of 20wt% for vermiculites, the highest absorption coefficient can be found under the 15wt%. On the other hand, acoustic impedance of composite material presented in this article will slowly decrease with frequencies, and the influences of these two parameters are focused on the lower frequency range.

In vitro estimation of pressure drop across tracheal tubes during high-frequency percussive ventilation

Tracheal tubes (TT) are used in clinical practice to connect an artificial ventilator to the patient's airways. It is important to know the pressure used to overcome tube impedance to avoid lung injury. Although high-frequency percussive ventilation (HFPV) has been increasingly used, the mechanical behavior of TT under HFPV has not yet been described. Thus, we aimed at characterizing in vitro the pressure drop across TT (ΔPTT) by identifying the model that best fits the measured pressure–flow (P–) relationships during HFPV under different working pressures (PWork), percussive frequencies and mechanical loads. Three simple models relating ΔPTT and flow were tested. Model 1 is characterized by linear resistive [Rtube ⋅ ] and inertial [I ⋅ ] terms. Model 2 takes into consideration Rohrer's approach [K1 ⋅ + K2 ⋅ ] and inertance [I ⋅ ]. In model 3 the pressure drop caused by friction is represented by the non-linear Blasius component [Kb ⋅ ] and the inertial term [I ⋅ (t)]. Model 1 presented a significantly higher root mean square error of approximation than models 2 and 3, which were similar. Thus, model 1 was not as accurate as the latter, possibly due to turbulence. Model 3 presented the most robust resistance-related coefficient. Estimated inertances did not vary among the models using the same tube. In conclusion, in HFPV ΔPTT can be easily calculated by the physician using model 3.

Impedance Induce Valve Pump in Closed Loop System

This paper summarises a study which aims to develop and analyze the performance of the valveless impedance pump. Mechanism of valveless impedance pump is to apply acoustic impedance mismatch in order to drive the flow and also consists of a flexible connection at the ends to the more rigid sections. Characteristics of liquid velocity and pressure at the pump base valveless impedance at various supply voltage and different frequencies have been discovered through experimentation. Secondly, this research also aims to discuss the effect volume flow rate (millitres / min) in the elastic tube impedance based on different parameters of the pump pinch. The variation of pinch location and pinch width are also available through the results of this study. This study begins with the design set up to use the software and followed by installing all equipment used for the experiments. Then, this study continues to get results and make an analysis of the impedance pump by experimentation. Results found that all the parameters used in this experiment affect the flow rate in the impedance pump. Additional experiments on the effect of the thickness of the flexible tube on the flow rate gave lower values when the flexible tube is relatively thicker.

The strontium-vapor laser pumping efficiency under running-wave excitation

The effect of the design features of the gas-discharge tube on the processes proceeding in the discharge circuit of a metal-vapor laser has been investigated. The position of electrodes in the gas-discharge tube has been found to significantly affect the processes at work in the discharge circuit and the energy characteristics of the laser. For instance, gas-discharge tubes with electrodes placed in the hot region of the discharge channel are typified by high metastable-population rates at the leading edge of the excitation pulse, whereas with electrodes positioned in cold buffer regions, the leading edge of the voltage pulse across the resistive component of the tube impedance is seen to peak. Conditions for running-wave generation in the active media of lasers on self-terminated transitions of metal atoms and the running-wave use efficiency for laser pumping are discussed, considering a strontium-vapor laser as an illustration. It is shown that the running wave is generated as the result of the breakdown in the anode end of the gas-discharge tube and is maintained by the energy stored in the capacitive component of the impedance of the gas-discharge tube. The lasing pulse duration under running-wave excitation corresponds to the time it takes an ionization wave to propagate from the anode to the cathode of the gas-discharge tube, with pumping efficiency being ~6-8% for a strontium-vapor laser. The average lasing power varies within 10-15% depending on whether the totally reflecting cavity mirror is placed near the anode or the cathode of the tube.

Multilayer tube impedance and external radiation

The paper describes a method for calculating the longitudinal and transverse impedances of the laminated round pipe with many layers of different materials. The charge is moving along the pipe axis with arbitrary constant velocity. The study is based on the field-matching technique applied for the arbitrary harmonic of the electromagnetic field. The matrix formalism has been developed to describe the field transitions through the subsequent layers that allow coupling the electromagnetic fields inside and outside the pipe. The number of equations to be solved is then reduced to four algebraic equations. The solutions and ultrarelativistic limits for the field harmonics in the inner and outer regions of the pipe are derived.

Low-Frequency Noise of Resistively Coupled Charge Amplifiers

In resistive wire position sensitive neutron detector systems two charge sensitive preamp inputs are connected via the tube impedance. Due to this coupling the output noise increases significantly. This work investigates the behavior of that kind of coupling induced noise using a technique called "noise gain calculation". The output noise correlation is analyzed analytically. Attained results are cross checked via simulations and measurements. Conclusions are drawn to better understand system resolution estimation for coupled preamplifier designs.

Wind instruments: Some unanswered questions.

The basics of functioning and tuning of wind instruments is reasonably explained by small‐amplitude descriptions. Some details must be cleared up, such as corrections at the hole/bore transition, bends, and radiation at hole ends. In some cases, however, the linear description fails. For example, a clarinet becomes unplayable when its usual holes are replaced by much smaller and shorter ones (of the same impedance) [D. H. Keefe, J. Acoust. Soc. Am. 73, 1804–1820 (1983)]. Since it was noted that this tube could be blown with another (i.e., a saxophone) mouthpiece, it was supposed that the superimposed static flow influences the tube impedance. This assumption was provisionally confirmed by measurements. Understanding this phenomenon may help to improve the ease of playing of the lowest notes on saxophones. The common quantitative description of the flute action does not explain why certain fork fingerings cannot be blown and why the ‘‘reed‐flute’’ has a dominating fifth harmonic in its initial transient. To contribute to the discussion on the influence of wall vibrations on tone quality, a mechanism will be proposed which is possibly responsible for a coupling between air and wall vibrations.

Spatial and temporal evolution of the electric field in a longitudinally electric-discharge-pumped gas laser: Application to a large-bore copper vapor laser

Calculations of the electric field in the excitation pulse of a 8-cm-diam copper-vapor laser are presented. The electric field evolution is governed by a diffusion equation. Both radial and axial diffusions are considered. The boundary conditions are determined by the geometry of the tube, which is coaxially shielded by a metal sleeve, considering the tube inductance and parasitic capacitance. The diffusion coefficients are determined by the electrical conductivity of the plasma that is calculated based on measured plasma parameters. These calculations are essential both for modeling the excitation process and for estimation of the overall tube impedance in such lasers. Inadequate penetration of the electric field into the plasma because of high pre-pulse conductivity turns out to be a main cause of power and pulse repetition rate limitations of this laser. The optimization of the tube geometry in order to minimize the field penetration problem is discussed.

Analysis of the impedance of a coaxial, large-bore copper-vapor laser

The impedance of the laser head of a 100-W copper-vapor laser is investigated. The laser head is of a coaxial geometry, which is commonly used for longitudinally electrically excited, pulsed-gas lasers. The plasma conductivity is estimated using the available data on plasma parameters. The effect of radial gradient of the gas temperature and electron density is considered. The tube inductance and capacitance are estimated and the combined effect is demonstrated. The skin effect is considered. A method to calculate the exact influence of the skin effect on the tube impedance is presented. The full calculation procedure is demonstrated for the case of a 100-W, 8-cm-diameter, copper-vapor laser. The consequent impedance is used to calculate the laser current under given excitation conditions. Very good agreement exists between the calculated and measured laser current. The metal-sleeve diameter is found that is optimal for power matching.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Analysis of the accuracy of respiratory impedance measurements on tubes and in man

The accuracy of respiratory impedance measurements by a previously described device is estimated. A theory for calculation of tube impedance is considered. The standard deviations of real, imaginary parts and module of tubal impedance are about 0.1 hPa/(l/s). The mean experimental values are in the range of theoretical curves for this kind of tube. Thus, the measurements are in a good agreement with theoretical calculations. When the impedance of the human respiratory system is measured, the mean individual standard deviations of real and imaginary parts of impedance are about 0.5 hPa/(l/s), which is equal to 20% of the real impedance. Causes of measurement deviations and ways of their decrease are also analyzed.

Simulation of flow through a parametrized “reed‐aperture”

In systems used to simulate wind instrument behavior the blowing pressure is often set to some constant value. This is equivalent to assuming that the blowing pressure source (lungs‐bronchi‐trachea‐vocal tract) has an internal impedance that is small in comparison with reed‐aperture plus tube impedance. A stylized pressure source plus reed‐aperture plus tube is simulated to investigate the effects of source characteristics and tube characteristics. The pressure source is represented by one of four configurations: large cross‐sectional area vocal tract, small cross‐sectional area vocal tract, an /a/‐shaped tract, and an /i/‐shaped tract. The rectangular “reed‐aperture” is parametrized so that its time variation is independent of any source or tube loading. Four “tube” loadings are simulated: a zero impedance, a resistance, an inertance, and a section of uniform tubing. Waveforms and spectra are calculated for air flow through the reed‐aperture, blowing pressure, and tube pressure for the 4 × 4 = 16 possible combinations to demonstrate the effects of source and tube characteristics.

Influence of radiation fluctuations on plasma tube impedance variations of a CO2 laser

Influence of radiation fluctuations on plasma tube impedance variations of a CO2 laser

Influence of radiation fluctuations on plasma tube impedance variations of a CO2 laser

A model for the correlation of the lasing action and the ionisation processes of a CO2 laser is presented. The model takes into account the step ionisation of N2 and CO molecules. Making use of the method of rate equations the expressions of the correlation between the laser output power variations and the discharge impedance changes, as well as spontaneous light intensity changes, are obtained.

Some Characteristics of a 600 kV Flash X-ray Tube

The performance of a continuously pumped flash X-ray tube has been studied in the voltage range 250-600 kV. Dose, pulse length, beam quality, source size and spatial distribution of the radiation were measured. It is shown that the output intensity is maximized if the tube impedance is 2.3 times the internal impedance of the pulser.