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The human ear canal couples the external sound field to the eardrum and the solid parts of the middle ear. Therefore, knowledge of the acoustic impedance of the human ear is widely used in the industry to develop audio devices such as smartphones, headsets, and hearing aids. In this study acoustic impedance measurements in the human ear canal of 32 adult subjects is presented. Wideband measurement techniques developed specifically for this purpose enable impedance measurement to be obtained in the full audio band up to 20kHz. Full ear canal geometries of all subjects are also available from the first of its kind in vivo based magnetic resonance imaging study of the human outer ear. These ear canal geometries are used to obtain individual ear moulds of all subjects and to process the data. By utilizing a theoretical Webster's horn description, the measured impedance is propagated in each ear canal to a common theoretical reference plane across all subjects. At this plane the mean human impedance and standard deviation of the population is found. The results are further demographically divided by gender and age and compared to a widely used ear simulator (the IEC711 coupler)., Comment: 40 pages, 13 figures. Submitted to JASA

The multimedia evolution has led to increased audio signal bandwidth in new generations of smartphones, headsets, headphones, as well as hearing aids. Full audio bandwidth performance, up to 20 kHz, is required. This calls for wider band performance of the ear simulators, and head and torso simulators used by the industry to evaluate these multimedia devices, as well as a better understanding of the high frequency behaviour of the human ear that these simulators are supposed to replicate. Acoustic input impedance measurements are an important parameter when characterizing small complex cavities such as ear simulators and the human ear. Today, this is well covered up to around 8-10 kHz. In this study a calibration procedure for measuring wideband impedance is developed, that uses multiple reference loads each defined by a detailed simulated impedance, in order to increase the applicable frequency bandwidth of the measurements. Comparing measured impedance magnitude, calibrated with this new procedure, to detailed simulations on a widely used ear simulator (IEC711 coupler) shows good agreement in the full audio bandwidth. Furthermore, the calibration procedure is streamlined to make it suited for a larger scale impedance study of the human ear, and measurements in one human ear is presented., Comment: 36 pages, 11 figures. Submitted to JASA

Light management is of great importance to photovoltaic cells, as it determines the fraction of incident light entering the device. An optimal pn-junction combined with an optimal light absorption can lead to a solar cell efficiency above the Shockley-Queisser limit. Here, we show how this is possible by studying photocurrent generation for a single core-shell p-i-n junction GaAs nanowire solar cell grown on a silicon substrate. At one sun illumination a short circuit current of 180 mA/cm^2 is obtained, which is more than one order of magnitude higher than what would be predicted from Lambert-Beer law. The enhanced light absorption is shown to be due to a light concentrating property of the standing nanowire as shown by photocurrent maps of the device. The results imply new limits for the maximum efficiency obtainable with III-V based nanowire solar cells under one sun illumination., Comment: 19 pages, 3 figures

We have reproducibly contacted gated single wall carbon nanotubes (SWCNT) to superconducting leads based on niobium. The devices are identified to belong to two transparency regimes: The Coulomb blockade and the Kondo regime. Clear signature of the superconducting leads is observed in both regimes and in the Kondo regime a narrow zero bias peak interpreted as a proximity induced supercurrent persist in Coulomb blockade diamonds with Kondo resonances., Comment: Proceeding for International Symposium on Mesoscopic Superconductivity and Spintronics 2006, NTT BRL, Atsugi, Japan