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Kren Monrad Nørgaard

Kren Monrad Nørgaard
Interacoustics A/S

PhD

About

12
Publications
2,696
Reads
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88
Citations
Citations since 2017
12 Research Items
88 Citations
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Introduction
The aim of my research is to increase the practicality, reliability, reproducibility, and accuracy of various audiological measures and demonstrate such improvements. My current focus lies with ear-canal reflectance and otoacoustic emissions, and analyses include ideal ear simulators and real ear canals. My goal is not to explore the audiological or diagnostic utility of such measures, but rather to enable researchers and clinicians to do so through new and improved measurement methods.

Publications

Publications (12)
Article
Full-text available
Measurements of wideband acoustic immittance (WAI) rely on the calibration of an ear probe to obtain its acoustic source parameters. The clinical use of WAI and instruments offering the functionality are steadily growing, however, no international standard exists to ensure a certain reliability of the hardware and methods underlying such measuremen...
Article
Full-text available
Measuring ear-canal absorbance and compensating for effects of the ear-canal acoustics on otoacoustic-emission measurements using an ear probe rely on accurately determining its acoustic source parameters. Using pressure measurements made in several rigid waveguides and models of their input impedances, a conventional calibration method estimates t...
Article
Full-text available
Causality is a fundamental property of physical systems and dictates that a time impulse response characterizing any causal system must be one-sided. However, when synthesized using the inverse discrete Fourier transform (IDFT) of a corresponding band-limited numerical frequency transfer function, several papers have reported two-sided IDFT impulse...
Article
Full-text available
Clinical diagnostic applications of ear-canal reflectance have been researched extensively in the literature, however, the measurement uncertainty associated with the conventional measurement technique using an insert ear probe is unknown in human ear canals. Ear-canal reflectance measured using an ear probe is affected by multiple sources of error...
Article
Full-text available
Ear-canal reflectance has been researched extensively for diagnosing conductive hearing disorders and compensating for the ear-canal acoustics in non-invasive measurements of the auditory system. Little emphasis, however, has been placed on assessing measurement accuracy and variability. In this paper, a number of ear-canal-reflectance measurement...
Article
Full-text available
Ear-canal reflectance is useful for quantifying the conductive status of the middle ear because it can be measured non-invasively at a distance from the tympanic membrane. Deriving the ear-canal reflectance requires decomposing the total acoustic pressure into its forward- and reverse-propagating components. This decomposition is conveniently achie...
Article
Full-text available
Measurements of the ear-canal reflectance using an ear probe require estimating the characteristic impedance of the ear canal in situ. However, an oblique insertion of the ear probe into a uniform waveguide prevents accurately estimating its characteristic impedance using existing time-domain methods. This is caused by the non-uniformity immediatel...
Article
Full-text available
Evanescent waves emerge from a small sound source that radiates into a waveguide with a larger cross-sectional area, but unlike planar waves, do not propagate far from the source. Evanescent waves thus contaminate in-ear calibration of acoustic stimuli. Measurements with an otoacoustic-emission (OAE) probe inserted at the entrance of long tubes of...
Article
Full-text available
The calibration of ear-probe microphones can increase the precision of calibrating stimulus levels in situ and of measuring acoustic responses from the ear. This paper proposes a methodology to measure the sensitivity of an ear-probe microphone, requiring only an acoustic coupler and a calibrated reference microphone. The input impedance of the cou...
Article
Full-text available
The calibration of an ear probe to determine its Thévenin-equivalent acoustic source parameters facilitates the measurement of ear-canal impedance and reflectance. Existing calibration error metrics, used to evaluate the quality of a calibration, are unable to reveal undesired parallel components in the source parameters. Such parallel components c...
Article
Full-text available
The ear-canal acoustic impedance and reflectance are useful for assessing conductive hearing disorders and calibrating stimulus levels in situ. However, such probe-based measurements are affected by errors due to the presence of evanescent modes and incorrect estimates or assumptions regarding characteristic impedance. This paper proposes a method...
Article
Full-text available
This paper proposes an alternative approach to acoustic Thévenin calibration of an ear probe. An existing methodology derives the Thévenin-equivalent source parameters from the measured probe pressures in a number of short waveguides by solving an overdetermined system of equations. This existing methodology is affected by errors caused by evanesce...

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