Specification of the geometry of the human ear canal for the prediction of sound-pressure level distribution

The geometry of 15 human ear canals has been studied. Silicone rubber molds were made of the ear canals of human cadavers, and a mechanical probe system was used to obtain approximately 1000 coordinate points over the surface of each mold. The data points were accurate to about 0.03 mm in each of the three space directions, allowing ample resolution of surface detail. The measurements have been summarized as individual ear canal area functions, the area of cross-sectional slices normal to a curved central axis following the bends of the canal. Large intersubject differences were found, but several overall trends were evident in the area functions. Accurate specification of the canal geometry has lead to improved predictions of the sound-pressure distribution along the human ear canal at frequencies greater than 8 kHz. Such predictions are relevant to the development of high-frequency audiometric methods, high-fidelity hearing aids, and to the interpretation of experiments in physiological and psychological acoustics.     

The spatial distribution of sound pressure within scaled replicas of the human ear canal

A theoretical model for calculating the variation of sound pressure within the ear canal is presented. The theory is an extension of the horn equation approach, and accounts for the variation of cross-sectional area and curvature of the ear canal along its length. Absorption of acoustic energy at the eardrum is included empirically through an effective eardrum impedance that acts at a single location in the canal. For comparison, measurements of the distribution of sound pressure have been made in two replica ear canals. Both replicas have geometries that duplicate, as nearly as possible, that of a real human ear canal, except that they have been scaled up in size to increase the precision of measurements. One of the replicas explicitly contains a load impedance to provide acoustical absorption at a single eardrum position. Agreement between theory and experiment was good. It is clear that at higher frequencies (above about 6 kHz in human ear canals), this theoretical approach is preferable to the more usual "uniform cylinder" approximation for the ear canal. At higher frequencies, there is no unique eardrum pressure; rather, very large variations of sound pressure are found over the tympanic membrane surface.     

Measurement of cavity polariton dispersion curve

We study the photoluminescence of quantum well excitons imbedded in monolithic microcavities. In the strong coupling regime, a coupled-mode situation develops, the cavity-polariton. We describe a model of the photoluminescence phenomenon in this regime, which by comparison with experiments enables us to determine the cavity-polariton dispersion curve. An excellent agreement with our theoretical model is found.     

Transformation of sound-pressure level from the free field to the eardrum presented in numerical form

In an earlier work [E. A. G. Shaw, J. Acoust. Soc. Am. 56, 1848-1861 (1974)], self-consistent families of curves which best fitted the experimental data from 12 studies were presented to show the average sound-pressure transformation from the free field to the human eardrum in the horizontal plane. Tabulated values of azimuthal dependence at 15-deg intervals in azimuth and transformation to the eardrum at 0 degree azimuth are given at 43 selected frequencies between 0.2 and 12 kHz. These values are self-consistent within 0.1 dB.     

Measurement of CrO in flames by cavity ringdown spectroscopy

CrO is an important intermediate in the high temperature oxidation chemistry of chromium containing species. This work reports the first detection of CrO in a flame. The B⁵-X⁵ electronic transition was probed by cavity ringdown spectroscopy (CRDS) in a lean (=0.38), low-pressure, flat, laminar hydrogen-oxygen-argon flame seeded with Cr(CO)₆. The previous B⁵-X⁵ CrO spectrum of Hocking et al. (605.0 nm-606.5 nm) is extended from the band head located at 605.6 nm to 614.4 nm. The temperature profiles of the doped and undoped flames were obtained from measurements of OH laser- induced fluorescence. Seeding the flame with Cr(CO)₆ increased the flame temperature by approximately 150 K. The concentration profile of CrO was measured as a function of height above the burner. CrO absorption signals were converted to concentration using the measured temperature profile and absorption cross-section calculated from lifetimes by Hedgecock et al. A lower limit peak CrO concentration of 1.6 ppb was found in the flame. Some uncertainty in the cross-section remains. Comparisons to calculations using STANJAN indicate that CrO is present in flames at super equilibrium concentrations. PACS 82.33.Vx; 42.62.Fi     

The evolution of field distribution in a dynamic cavity

The results of calculations of the dynamics of a field in a cavity that consists of a stationary mirror and a periodically displacing mirror are presented. The initial distribution of the field corresponds to the equilibrium thermal (Planck) distribution. It is shown that, if conditions of a resonant excitation are implemented, pulses can be formed the degree of unipolarity of which increases from the initial zero degree to an almost maximum (unit) degree.     

Adjusting the accelerating field distribution of a superconducting CH cavity

In a superconducting CH (cross bar H mode) cavity, the method of regulating the length of a drift tube is employed to adjust the distribution of the accelerating field. In this article, we simulate the electromagnetic field of a CH structure to illustrate the reason for adjusting the field distribution by varying drift tube length. Meanwhile, that the presence of the drift tube will cause a sharp rise in the maximum electric field is also shown. This phenomenon is contrary to superconducting cavity design principles in which the cavity geometry needs to be optimized to reduce the maximum electric field to avoid field emission. We propose a variable diameter superconducting CH cavity design to solve this conflict. The simulation of the variable diameter superconducting CH cavity shows that this method is feasible.     

Measurement of the residual birefringence of interferential mirrors using Fabry-Perot cavity

Received: 23 September 1996/Revised version: 10 January 1997     

Controlled hole burning in the photon-number distribution of field states in a cavity

A feasible experimental scheme to generate states of a field mode in a high-Q cavity possessing holes in their photon-number distributions at controlled positions is proposed. Such kind of states may be of interest to optical data storage and communications with a possible readout system consisting of an atomic deflection setup.     

基于发射光谱的DF激光器光腔温度与粒子数分布

 建立了谱线增益系数与温度、粒子数分布之间及谱线增益系数与谱线强度之间的关系式,对一台燃烧驱动DF激光器的发射光谱进行了测量,利用发射光谱数据计算得到光腔温度为381.4 K,分布在振动态能级1与0,振动能级2与1,振动能级3与2的粒子数之比分别为0.60～0.62, 0.676 4, 0.71～0.74。     

Interactions of several replicas in the random field Ising model

The replicated field theory of the random field Ising model involves the couplings of replicas of different indices. The resulting correlation functions involve a superposition of different types of long distance behaviours. However the n = 0 limit allows one to discuss the renormalization group properties in spite of this phenomenon. The attraction of pairs of replicas is enhanced under renormalization flow and no stable fixed point is found. Consequently, an instability occurs in the paramagnetic region, before one reaches the Curie line, signalling the onset of replica symmetry breaking. Received 28 July 2000     

Initial bioadhesion on surfaces in the oral cavity investigated by scanning force microscopy

Scanning force microscopy (SFM) was used to measure the adhesion forces between BSA, a saliva protein, and two dental surfaces, natural enamel and a filling material (Dyract AP™). Measurements were taken in phosphate buffered aqueous solutions (PBS). Forces were resolved down to the piconewton regime. The dependency of the adhesion force on the interaction time, pH-value and substrate surface was monitored. In a further step, surface samples were fixed on an enamel brace and carried for a defined time in the oral cavity. The formed biofilm, called pellicle, shows a different morphology on the different substrates. This can be explained by the above-mentioned substrate dependence of the adhesion force.     

Measurement of temperature distribution in thermocapillary instability

Summary We report the measurement of the temperature field inside a fluid layer with a free surface, heated from below, in the unstable regime (thermocapillary instability or Marangoni effect). The measurements have been done when the convective flow was time dependent. We show the evolution of the temperature spatial distribution in the periodic and biperiodic regimes. We also discuss the main differences of the temperature field between Rayleigh-Benard and Marangoni instabilities.

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Riassunto Si riporta la misura del campo di temperatura in uno strato di fluido scaldato dal di sotto e con una superficie libera nel regime instabile (instabilità termocapillare o effetto Marangoni). Le misure sono state effettuate quando il moto convettivo non era stazionario. L’evoluzione della distribuzione spaziale della temperatura è stata seguita nel regime periodico e biperiodico. Si discutono inoltre le prineipali differenze del campo di temperatura fra l’instabilità di Rayleigh-Benard e quella di Marangoni.

     

Time resolved measurements of the energy distribution in unstable plasma II. Measurement in the ionization waves

A sampling technique described in Part I has been used, for measurement of the electron distribution function. Two groups of electrons and changes of the distribution function along the ionization waves of small amplitude have been found.The authors wish to acknowledge the support afforded them by Professor Dr. V. Kunzl.     

Time resolved measurements of the electron energy distribution in unstable plasma I. Measurement technique

In this paper the sampling technique for the direct measurement of the second derivative of the Langmuir probe characteristic is described. It enables the study of the variation of the distribution function in the time-unstable plasma. The tests of the method and the discussion of its results are given.The authors desire to acknowledge the support afforded them by Professor Dr. V. Kunzl.     

Measurement of the total energy distribution in photo-induced field emission

Accurate measurements of the total energy distribution of excited electrons in photoinduced field emission are needed to determine the mechanism of photo-excitation. Experimental measurements of the total energy distributions involve a correction for instrumental broadening introduced by the energy analyzer. The usual assumption of a symmetric resolution function of gaussian form is not always adequate for a retardation-type energy analyzer. We describe a method, which involves measurements of the total energy distribution in direct field emission, whereby the instrumental broadening can be deconvoluted from the total energy distribution observed in photo-induced field emission. The method also yields an accurate determination of the total energies of photoemitted electrons relative to the Fermi level. The method is illustrated by applying it to deconvolute total energy distributions observed in a preliminary study of the shape of the photopeak in photo-induced field emission.     

Measurement of ɛ and tan δ by the perturbation method in a rectangular cavity

These measurements are considered for circular and rectangular rods, and also flat plates; relative methods are used, in order to simplify the technique and increase the accuracy. Test results are given.