Standing wave patterns in the human ear canal used for estimation of acoustic energy reflectance at the eardrum

Standing wave patterns were measured in the unoccluded ear canals of 13 human subjects, for applied pure tones of 3 to 13 kHz. Measurements were made, using a probe microphone technique, over a region which could be approximated as a duct of constant cross-sectional area. Analysis of the patterns allowed the reflective properties of the middle ear to be determined in terms of an acoustic energy reflection coefficient, or reflectance, at the eardrum. Over all subjects the trend of the results was for the energy reflection coefficient to rise from about 0.3 at 4 kHz up to 0.8 at 8 kHz, and continue at this value to 13 kHz. There was, however, significant intersubject variation, especially at frequencies greater than 7 kHz.     

A hierarchy of examples illustrating the acoustic coupling of the eardrum

Basic principles underlying the acoustic coupling of the eardrum are illustrated in the form of a hierarchy of examples ranging from a simple piston coupled to a semi-infinite acoustic duct, to a flexible partition coupled to a variable cross-section duct, and to a closed cavity. The hierarchy illuminates some of the limitations of various simplified elements commonly used to model the middle ear and demonstrates the necessity of treating the acoustics and the eardrum as an integrated subsystem. Results show that the tympanic cavity and the secondary middle-ear air chambers contribute fundamental features to the acoustic coupling of the ear. The nature of the acoustic coupling limits the passive energy absorption and transmission properties of the eardrum. The magnitude and frequency dependence of the energy dissipation within the ultrastructure of the partition, due to bending and transverse deflection, is discussed in analogy to possible dissipation mechanisms within the eardrum itself. Examples are provided for several simple systems reproducing some of the gross anatomical characteristics of the cat eardrum.     

Measurement of the eardrum impedance of human ears

The determination of an acoustical impedance requires measurements of pressure and volume velocity. As no direct method is available for measuring velocity in an ear canal, a technique was developed which is based on pure pressure measurements. The ear canal is used as a measuring tube, the area function of which is also deduced from the pressure measurements. High-frequency measurements in living subjects involve many sources of errors. A criterion for deciding if a good measurement has been made is given. The technique of measurements is described, regarding both the use of probe tube microphones and the computer aided data recording. Finally, the results are presented, and some comments are given. A reliable interpretation of the results seems to be impossible because of lack of our knowledge of the middle ear function at high frequencies.     

Estimation of eardrum acoustic pressure and of ear canal length from remote points in the canal

Sound pressure distributions in the human ear canal, whether unoccluded or occluded with ear molds, were studied using a probe tube technique. On average, for frequencies below 6 kHz, the measuring probe tube had to be placed within 8 mm of the vertical plane containing the top of the eardrum (TOD), determined optically, in order to obtain sound pressure magnitudes within 6 dB of "eardrum pressure." To obtain that accuracy in all of the eight subjects studied, the probe had to be within 6 mm of the TOD. Since probe location relative to the drum has to be known, a purely acoustic method was developed which can be conveniently used to localize the probe-tip position, utilizing the standing wave property of the sound pressure in the ear canal. The acoustically estimated "drum location" generally lay between the optically determined vertical planes containing the TOD and the umbo. On average, the "drum location" fell 1 mm medial to the TOD. Of the 32 estimates made acoustically in various occluded and unoccluded conditions in 14 subjects, 30 estimates lay within a +/- 2-mm range of this average.     

Dynamical energy analysis for built-up acoustic systems at high frequencies

Standard methods for describing the intensity distribution of mechanical and acoustic wave fields in the high frequency asymptotic limit are often based on flow transport equations. Common techniques are statistical energy analysis, employed mostly in the context of vibro-acoustics, and ray tracing, a popular tool in architectural acoustics. Dynamical energy analysis makes it possible to interpolate between standard statistical energy analysis and full ray tracing, containing both of these methods as limiting cases. In this work a version of dynamical energy analysis based on a Chebyshev basis expansion of the Perron-Frobenius operator governing the ray dynamics is introduced. It is shown that the technique can efficiently deal with multi-component systems overcoming typical geometrical limitations present in statistical energy analysis. Results are compared with state-of-the-art hp-adaptive discontinuous Galerkin finite element simulations.     

New energy estimates of extensive air showers using signals detected at great distances from the shower axis

On the basis of detailed tables of signals from Yakutsk extensive air shower scintillation detectors that were calculated using the GEANT4 package, the numerical evaluation of the energy E _θ of inclined extensive air showers has been obtained using a pilot signal at a distance of 1000 m from the shower axis and the known zenith angle θ using the CORSIKA package. This original estimate was obtained without using the method of cutting the signal spectra according to lines of equal intensity. We also obtained the values of practical units of measure for signals in ground-based and underground detectors.     

Ear-canal acoustic admittance and reflectance effects in human neonates. I. Predictions of otoacoustic emission and auditory brainstem responses

This report describes the extent to which ear-canal acoustic admittance and energy reflectance (YR) in human neonates (1) predict otoacoustic emission (OAE) levels and auditory brainstem response (ABR) latencies, and (2) classify OAE and ABR responses as present or absent. Analyses are reported on a subset of ears in which hearing screening measurements were obtained previously [Norton et al., Ear. Hear. 21, 348-356 (2000a)]. Tests on 1405 ears included YR, distortion-product OAEs, transient-evoked OAEs, and ABR. Principal components analysis reduced the 33 YR variables to 5-7 factors. OAE levels decreased and ABR latencies increased with increasing high-frequency energy reflectance. Up to 28% of the variance in OAE levels and 12% of the variance in ABR wave-V latencies were explained by these factors. Thus, the YR response indirectly encodes information on inter-ear variations in forward and reverse middle-ear transmission. The YR factors classify OAEs with an area under the relative operating characteristic (ROC) curve as high as 0.79, suggesting that middle-ear dysfunction is partly responsible for the inability to record OAEs in some ears. The YR factors classified ABR responses less well, with ROC areas of 0.64 for predicting wave-V latency and 0.56 for predicting Fsp.     

Spectral moment estimates of broadband backscattering acoustic wave in moving medium

I.IntroductionSincemiddle198o's,theacousticDopplercurrentprofiler(ADCP)hasbeenusedinvariousaspects.Itnormallytransmitsasine-modulatedpulse,thenmeasurestheechoofmanylayersinaprofile.TheDopplerfrequencyshiftofeachlayeriscalculatedwhilethevesseliscruisingandADCPiscontinuallytransmittingpulsesandreceivingechoes.BystatisticallyaveragingtheDopplerfrequencyshiftofeachlayerinmultipletransmissions,theestimateofDopplerfrequencyshiftofthatlayerisobtained,thenthevelocityestimatesofmanydepthbinsinapr…     

Ear-canal acoustic admittance and reflectance measurements in human neonates. II. Predictions of middle-ear in dysfunction and sensorineural hearing loss

This report describes relationships between middle-ear measurements of acoustic admittance and energy reflectance (YR) and measurements of hearing status using visual reinforcement audiometry in a neonatal hearing-screening population. Analyses were performed on 2638 ears in which combined measurements were obtained [Norton et al., Ear Hear. 21, 348-356 (2000)]. The measurements included distortion-product otoacoustic emissions (DPOAE), transient evoked otoacoustic emissions (TEOAE), and auditory brainstem responses (ABR). Models to predict hearing status using DPOAEs, TEOAEs, or ABRs were each improved by the addition of the YR factors as interactions, in which factors were calculated using factor loadings from Keefe et al. [J. Acoust. Soc. Am. 113, 389-406 (2003)]. This result suggests that information on middle-ear status improves the ability to predict hearing status. The YR factors were used to construct a middle-ear dysfunction test on 1027 normal-hearing ears in which DPOAE and TEOAE responses were either both present or both absent, the latter condition being viewed as indicative of middle-ear dysfunction. The middle-ear dysfunction test classified these ears with a nonparametric area (A) under the relative operating characteristic curve of A = 0.86, and classified normal-hearing ears that failed two-stage hearing-screening tests with areas A = 0.84 for DPOAE/ABR, and A = 0.81 for TEOAE/ABR tests. The middle-ear dysfunction test adequately generalized to a new sample population (A = 0.82).     

Baryon acoustic oscillation intensity mapping of dark energy

The expansion of the Universe appears to be accelerating, and the mysterious antigravity agent of this acceleration has been called "dark energy." To measure the dynamics of dark energy, baryon acoustic oscillations (BAO) can be used. Previous discussions of the BAO dark energy test have focused on direct measurements of redshifts of as many as 10(9) individual galaxies, by observing the 21 cm line or by detecting optical emission. Here we show how the study of acoustic oscillation in the 21 cm brightness can be accomplished by economical three-dimensional intensity mapping. If our estimates gain acceptance they may be the starting point for a new class of dark energy experiments dedicated to large angular scale mapping of the radio sky, shedding light on dark energy.     

The correlation of the energy resolution of incident light with the measured reflectance of multilayers

This paper presents an expression for describing the correlation of the energy resolution of incident light with the measured reflectance of multilayers, and gives a new method for calculating the polychromatic-light reflectance of multilayers. Using this method we give the reflectance spectrum of some multilayers in the case in which the incident light is polychromatic. The theoretical analysis shows that for the multilayers of a given design the peak reflectance of the polychromatic light is smaller than that of the monochromatic light, but no-peak reflectance of the polychromatic light is bigger than that of the monochromatic light. Further, the measured reflectance spectrum will be a line if the energy resolution is less than a decided value. The shorter the design-wavelength of the multilayer, the stronger the effect of the energy resolution on the reflectance.     

Frequency domain expressions for the estimation of time-averaged acoustic energy density

This paper builds on earlier work by the same authors to derive expressions for the time-averaged acoustic energy density in the frequency domain using the auto- and cross-spectral densities of multiple microphone elements. Expressions for the most common three-dimensional geometric arrangements are derived. Simplified expressions for use with two channel spectrum analysers are also presented.     

Rate of energy loss to intravalley acoustic modes in a degenerate surface layer at low lattice temperatures

The rate of loss of the energy of non-equilibrium electrons due to inelastic interaction with intravalley acoustic phonons in a degenerate surface layer is calculated for low temperatures when the approximations of the well-known traditional theory are not valid. The loss characteristics for GaAs and Si seem to be significantly different compared to what follows from the traditional approximations.     

Investigation of acoustic cavitation energy in a large-scale sonoreactor

Acoustic cavitation energy distributions were investigated for various frequencies such as 35, 72, 110 and 170 kHz in a large-scale sonoreactor. The energy analyses were conducted in three-dimensions and the highest and most stable cavitation energy distribution was obtained not in 35 kHz but in 72 kHz. However, the half-cavitation-energy distance was larger in the case of 35 kHz ultrasound than in the case of 72 kHz, demonstrating that cavitation energy for one cycle was higher for a lower frequency. This discrepancy was due to the large surface area of the cavitation-energy-meter probe. In addition, 110 and 170 kHz ultrasound showed a very low and poor cavitation energy distribution. Therefore larger input power was required to optimize the use of higher frequency ultrasound in the sonoreactor with long-irradiation distance. The relationship between cavitation energy and sonochemical efficiency using potassium iodide (KI) dosimetry was best fitted quadratically. From 7.77 × 10^?10 to 4.42 × 10^?9 mol/J of sonochemical efficiency was evaluated for the cavitation energy from 31.76 to 103. 67 W. In addition, the cavitation energy attenuation was estimated under the assumption that cavitation energy measured in this study would be equivalent to sound intensity, resulting in 0.10, 0.18 and 2.44 m^?1 of the attenuation coefficient (α) for 35, 72 and 110 kHz, respectively. Furthermore, α/(frequency)² was not constant, as some previous studies have suggested.     

Nonlinear optimization of acoustic energy harvesting using piezoelectric devices

In the first part of the paper, a single degree-of-freedom model of a vibrating membrane with piezoelectric inserts is introduced and is initially applied to the case when a plane wave is incident with frequency close to one of the resonance frequencies. The model is a prototype of a device which converts ambient acoustical energy to electrical energy with the use of piezoelectric devices. The paper then proposes an enhancement of the energy harvesting process using a nonlinear processing of the output voltage of piezoelectric actuators, and suggests that this improves the energy conversion and reduces the sensitivity to frequency drifts. A theoretical discussion is given for the electrical power that can be expected making use of various models. This and supporting experimental results suggest that a nonlinear optimization approach allows a gain of up to 10 in harvested energy and a doubling of the bandwidth. A model is introduced in the latter part of the paper for predicting the behavior of the energy-harvesting device with changes in acoustic frequency, this model taking into account the damping effect and the frequency changes introduced by the nonlinear processes in the device.     

Effective parameters and energy of acoustic metamaterials and media

An approach is proposed to describe a general form of acoustic media, in particular, acoustic metamaterials, based on their modeling with the simplest discrete periodic structures. The parameters of the discrete models, determined from the dispersion equation, are taken as the effective parameters of the modeled media. Transfer to an effective continuous medium is achieved by uniform distribution of these parameters over the length of the periodicity cell. It is shown that all of the wave motion characteristics of the medium, including the energy characteristics, are expressed through the effective parameters thus introduced. The necessary formulas are derived. Examples are given. The proposed method is useful for designing acoustic materials with the given wave properties.