James Randa

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Extracochlear electrical stimulation was carried out in 7 patients. We used square-wave signals. Electrode positions at the oval and round window showed the lowest current thresholds. The threshold of sound sensations elicited by electrical stimulation was higher in the high frequency than in the low frequency range. All 7 patients had hearing sensations(More)
Evoked otoacoustic emissions have been recorded from ears with high- and low/medium-frequency hearing losses using a simple technique with fixed stimulus intensity and no suppression of stimulus artifact. Ears with low/medium frequency hearing loss exceeding 40 dB HL generate responses ending before 17.5 ms after stimulus onset. This may be used for testing(More)
We report on the characterization of blackbody target reflections as part of the recent progress on the development of brightness temperature standards for microwave remote sensing at the National Institute of Standards and Technology. The very low reflections from the blackbody targets used in airborne or satellite remote sensing systems present challenges(More)
More than 50% of normal ears generate spontaneous otoacoustic emissions, which are sinusoidal tones originating in the cochlea. These faint sounds with levels typically at 10 dB to -30 dB are usually not recognized by the subjects who have them, but can be recorded by sensitive microphones in the ear canal. The clinical significance of having or not having(More)
The National Institute of Standards and Technology has developed the capability to measure noise parameters on a wafer in the 1–12.4-GHz range. We describe the measurement method and the uncertainty analysis and present results of measurements on a highly reflective transistor. Typical standard uncertainties are within the range of 20–25 K in Tmin, which is(More)
We report our recent progress toward the development of microwave brightness-temperature (BT) standards. As one of the crucial parameters, the target illumination efficiency (IE) was traditionally determined from the relative antenna pattern. We propose a measurement technique to extract the target IE solely by the use of passive radiometric measurements(More)
Accurate characterization of the brightness temperature (T_B) of black-body targets used for calibrating microwave remote-sensing radiometers includes many inputs: antenna pattern and loss, target temperature, target emissivity, mechanical alignment, and radiometric T_B measurements calibrated against physical standards. Here we describe measurements made(More)