Effects of ear-canal geometry and middle-ear pressure on wideband acoustic reflectance

Wideband acoustic immittance;Impedance;Reflectance;Middle ear;Horns;Area function;Negative middle-ear pressure;Pole-zero fitting;Acoustics;Eardrum;Ear canal;Tympanic membrane

Robinson, Sarah R

关键词: Wideband acoustic immittance;    Impedance;    Reflectance;    Middle ear;    Horns;    Area function;    Negative middle-ear pressure;    Pole-zero fitting;    Acoustics;    Eardrum;    Ear canal;    Tympanic membrane;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/99468/ROBINSON-DISSERTATION-2017.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

In this thesis, complex wideband acoustic immittance (WAI) measurements of the middle ear are studied. The body of work presented here has three major components: (1) design of a hearing measurement probe and probe tip, (2) extraction of the effects of the residual ear canal (REC) and estimation of the WAI at the tympanic membrane (TM), and (3) analysis of the TM-WAI to characterize middle-ear conditions. Major contributions of this thesis include a pole-zero modeling method to estimate WAI at the TM (Robinson et al., 2013), and analysis of changes in WAI with static negative middle-ear pressure (NMEP) (Robinson et al., 2016). Additionally, an extensive review of the literature and theory underlying WAI measurements is presented, using both time- and frequency-domain analyses.(1) Measurement probe: The design of a WAI measurement probe and probe tip was conducted with Mimosa Acoustics (Champaign, IL). The inclusion of this work in the present document is primarily limited to the probe-tip project. Two-port network modeling techniques were applied to describe and extract the effects of a variable-area probe tip on WAI measurement. This procedure is effective up to at least 3-5 [kHz], depending on the quality of the probe calibration.(2) Reflectance factorization: Complex reflectance data may be fit to a pole-zero model, and factored into its all-pass and minimum-phase parts, representing the lossless ear canal and complex middle-ear reflectance respectively (Robinson et al., 2013). This provides an intuitive analysis of reflectance, which is computationally efficient and adaptable to non-ideal (e.g. bandlimited or noisy) data. A detailed comparison is performed between this method and other TM-WAI estimation methods in the literature. (3) Negative middle-ear pressure (NMEP): Thompson et al. (2015) trained eight subjects with normal middle-ear function to induce consistent NMEPs, quantified by the tympanic peak pressure (TPP), to study the effects of NMEP on distortion-product otoacoustic emissions. WAI data were also collected in that study, and are analyzed in this thesis using the reflectance factorization method (Robinson et al., 2016). For the 8 ears presented here, NMEP has the largest and most significant effect across ears from 0.8 to 1.9 [kHz], resulting in reduced power absorbance by the middle ear and cochlea. On average, NMEP causes a decrease in the power absorbance level for low- to mid-frequencies, and a small increase above about 4 [kHz]. The effects of NMEP on WAI quantities, including the absorbance level and TM impedance, vary considerably across ears. The complex WAI at the TM and fitted model parameters show NMEP effects consistent with an increased stiffness in the middle ear, which could originate from the TM, tensor tympani, annular ligament, or other middle ear structures.