Kren Rahbek Nørgaard (Interacoustics/DTU) presents 'Compensating for oblique ear-probe insertions in ear-canal reflectance measurements'
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 immediately in front of the ear probe when inserted at an oblique angle, resembling a short horn loading, and introduces errors into the ear-canal reflectance. In this talk, I give an overview of the influence of oblique ear-probe insertions and show how they can be detected and quantified by estimating the characteristic impedance using multiple truncation frequencies, i.e., limiting the utilized frequency range. Additionally, I propose a method to compensate for the effects on reflectance of an oblique ear-probe insertion into a uniform waveguide. I estimate the incident impedance of the horn loading, i.e., were the uniform waveguide anechoic, which replaces the characteristic impedance when calculating reflectance. The method can compensate for an oblique ear-probe insertion into a uniform occluded-ear simulator and decrease the dependency of reflectance on insertion depth in an ear canal. However, more research is required to further assess the method in ear canals.