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Distortion-product emissions (DPEs) are tonal responses that may be detected in the ear canal when the ear is stimulated simultaneously by two tones that are closely spaced in frequency. In experimental animals, DPEs are reduced in amplitude or are eliminated when cochlear function is disrupted. This association has not been investigated in human subjects. This study was designed to investigate the relation of cochlear status, as determined by pure-tone behavioral thresholds, to DPE amplitude in human subjects. Forty men were selected as subjects. Twenty had normal hearing and 20 had high-frequency sensorineural hearing loss. Pure-tone behavioral thresholds were determined using conventional audiometric procedures for eight frequencies from 750 to 8000 Hz. DPEs were generated in the test ear of each subject by stimulating the ear with two tones, f1 and f2. The stimuli were selected to approximate audiometric test frequencies. Responses were detected by a sensitive microphone that was placed in the ear canal and were extracted by spectral analysis. Results of the study indicated that DPE amplitude was associated with pure-tone threshold. When audiometric threshold was ≤10 dB HL, DPEs could be elicited at all test frequencies for 98% of subjects in both groups. Mean maximum emission amplitude ranged from 3 to 13 dB SPL across frequency. When pure-tone threshold was above 50 dB HL, DPEs were absent or were significantly attenuated. DPEs varied in amplitude when audiometric threshold was between these two extremes. The association of DPE amplitude were pure-tone threshold was frequency specific. DPE amplitude was maximal when pure-tone thresholds were ≤10 dB HL and decreased as pure-tone behavioral threshold increased in the same subject. Repetition of the DPE protocol with five subjects from each group during separate test sessions indicated that the results were reliable over time. Results of the study have clinical implications. The technique may have potential as a noninvasive means of monitoring the status of the cochlea in human subjects.

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Thesis (Ph.D.)--University of Iowa, 2006. / Supervisor: J. Bruce Tomblin. Includes bibliographical references (leaves 92-99).

No description available.

Thesis (M.Clin.Audiol./Ph.D.)--University of Western Australia, 2005.

Yu, Shing. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 87-93). / Abstracts in English and Chinese; includes Chinese. / Abstract --- p.i / Acknowledgement --- p.vi / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Hearing impairment --- p.1 / Chapter 1.2 --- Limitations of existing CI --- p.2 / Chapter 1.3 --- Objectives --- p.3 / Chapter 1.4 --- Thesis Outline --- p.4 / Chapter 2 --- Background --- p.6 / Chapter 2.1 --- Signal Processing in CI --- p.6 / Chapter 2.1.1 --- Continuous Interleaved Sampler (CIS) --- p.7 / Chapter 2.1.2 --- Advanced Combination Encoder (ACE) --- p.12 / Chapter 2.2 --- Tone perception by cochlear implantees --- p.15 / Chapter 2.2.1 --- Pitch and Tone --- p.15 / Chapter 2.2.2 --- Mechanisms of pitch perception by cochlear im- plantees --- p.20 / Chapter 3 --- Tone-enhanced ACE Strategy for CI --- p.23 / Chapter 3.1 --- Basic principles --- p.23 / Chapter 3.2 --- Acoustical simulation with noise excited vocoder --- p.26 / Chapter 3.3 --- Implementation in a real CI system --- p.29 / Chapter 3.3.1 --- Technical details --- p.30 / Chapter 3.3.2 --- Visual comparison --- p.31 / Chapter 4 --- Robust Generation of F0 Trajectory --- p.33 / Chapter 4.1 --- Requirement on the F0 contour --- p.33 / Chapter 4.2 --- Extraction of F0 contour --- p.34 / Chapter 4.3 --- Post-processing of F0 contour --- p.36 / Chapter 4.3.1 --- Removal of octave-jump --- p.36 / Chapter 4.3.2 --- Interpolation --- p.36 / Chapter 4.3.3 --- Prediction --- p.36 / Chapter 4.3.4 --- Smoothing --- p.38 / Chapter 4.4 --- Performance evaluation --- p.38 / Chapter 5 --- Design of Listening Tests --- p.41 / Chapter 5.1 --- Speech Materials --- p.41 / Chapter 5.2 --- Testing modes --- p.43 / Chapter 5.2.1 --- Sound field mode --- p.45 / Chapter 5.2.2 --- Direct stimulation mode --- p.46 / Chapter 5.3 --- Test Interface --- p.47 / Chapter 6 --- Sound-field Tests --- p.49 / Chapter 6.1 --- Materials and Methods --- p.50 / Chapter 6.1.1 --- Subjects --- p.50 / Chapter 6.1.2 --- Signal processing and test stimuli --- p.52 / Chapter 6.1.3 --- Procedures --- p.52 / Chapter 6.2 --- Results --- p.54 / Chapter 6.3 --- Discussion --- p.57 / Chapter 7 --- Evaluation of Tone-enhanced Strategy --- p.59 / Chapter 7.1 --- Materials and Methods --- p.60 / Chapter 7.1.1 --- Subjects --- p.60 / Chapter 7.1.2 --- Signal processing and test stimuli --- p.60 / Chapter 7.1.3 --- Procedures --- p.62 / Chapter 7.2 --- Results --- p.63 / Chapter 7.3 --- Discussion --- p.66 / Chapter 8 --- Use of Automatically Generated F0 Contour --- p.72 / Chapter 8.1 --- Materials and Methods --- p.73 / Chapter 8.2 --- Results --- p.74 / Chapter 8.3 --- Discussion --- p.76 / Chapter 9 --- Conclusions --- p.80 / Chapter A --- LSHK Cantonese Romanization Scheme --- p.85 / Bibliography --- p.87

The acoustic reflex refers to the contraction of a middle ear muscle in response to sound. The contraction causes a stiffening of the middle ear system and, consequently, the flow of acoustic energy to the cochlea is impeded. By measuring the change in admittance in the auditory system during sound stimulation it is possible to indirectly monitor the middle ear muscle contractions. Such measurements provide useful information regarding the integrity of the auditory system and the location of the auditory pathology.