Quantifying how the sound delivered to the ear canal relates to hearing threshold has historically relied on acoustic calibration in physical assemblies with an input impedance intended to match the human ear (e.g., a Zwislocki coupler). The variation in the input impedance of the human ear makes such a method of calibration questionable. It is preferable to calibrate the acoustic signal in each ear individually. By using a calibrated sound source and microphone, the acoustic input impedance of the ear can be determined, and the sound delivered to the ear calibrated in terms of either (i) the incident sound pressure wave or (ii) that portion of the incident sound pressure wave transmitted to the middle ear and cochlea. Hearing thresholds expressed in terms of these quantities are reported, these in situ calibrations not being confounded by ear canal standing waves. Either would serve as a suitable replacement for the current practice of hearing thresholds expressed in terms of sound pressure level calibrated in a 6cc or 2cc coupler.

Objective Prevention of temporary threshold shift (TTS) after laboratory-based exposure to pure-tones, broadband noise, and narrow band noise signals has been achieved, but prevention of TTS under these experimental conditions may not accurately reflect protection against hearing loss following impulse noise. This study used a controlled laboratory-based TTS paradigm that incorporated impulsive stimuli into the exposure protocol; development of this model could provide a novel platform for assessing proposed therapeutics. Design Participants played a video game that delivered gunfire-like sound through headphones as part of a target practice game. Effects were measured using audiometric threshold evaluations and distortion product otoacoustic emissions (DPOAEs). The sound level and number of impulses presented were sequentially increased throughout the study. Study sample Participants were normal-hearing students at the University of Florida who provided written informed consent prior to participation. Results TTS was not reliably induced by any of the exposure conditions assessed here. However, there was significant individual variability, and a subset of subjects showed TTS under some exposure conditions. Conclusions A subset of participants demonstrated reliable threshold shifts under some conditions. Additional experiments are needed to better understand and optimize stimulus parameters that influence TTS after simulated impulse noise.

Objective(s): To investigate the differences in percutaneous versus passive transcutaneous bone-conduction stimulation in individuals with single-sided deafness. Study Design: Prospective, single-subject. Setting: Tertiary academic referral center. Patients: Adult bone-anchored implant listeners with single-sided deafness using a percutaneous implant system. Interventions: Experienced percutaneous bone anchored implant recipients were tested in the percutaneous and transcutaneous conditions using a BAHA 5 (Cochlear Corp., Cochlear Bone-Anchored Solutions, Mölnlycke, Sweden) sound processor on the patient's own abutment and on a softband. Main Outcome Measures: Phoneme recognition was assessed using Consonant-Nucleus-Consonant (CNC) words for soft (47 dB SPL) and average (62 dB SPL) speech inputs. Speech perception in noise performance was also assessed for soft (47 dB SPL) and average (62 dB SPL) speech inputs using sentences presented in multi-talker babble. Aided free-field thresholds were obtained in both conditions using warble tone stimuli. Results: Compared with percutaneous bone-conduction stimulation, transcutaneous stimulation demonstrated reduced effective gain for high frequency stimulation. Transcutaneous stimulation required higher signal to noise ratios to achieve comparable performance to the percutaneous condition. Phoneme recognition was poorer in transcutaneous versus percutaneous stimulation with the most significant impact observed for soft speech inputs. Conclusion: A significant performance gap in speech recognition is observed between percutaneous and transcutaneous bone-conduction stimulation in individuals with single-sided deafness at the same signal to noise ratios. Compared with percutaneous bone-conduction stimulation, transcutaneous stimulation demonstrated reduced effective gain, decreased phoneme recognition, word recognition, and performance in noise, with the most significant impact observed for soft speech inputs.

Transcranial attenuation (TA) of bone-conducted sound has a high degree of variability by frequency and subject, which may play a role in the objective benefit of individuals with single-sided deafness (SSD) treated with a bone-anchored implant (BAI). This study sought to determine whether TA is predictive of benefit in individuals with SSD who receive a BAI. Adult, English-speaking patients with unilateral profound sensorineural hearing loss who underwent a BAI evaluation were included for study. Absolute TA values were consistent with previously published reports. Regression analysis indicated no correlation between TA values and aided speech-in-noise performance for any combined or individual frequencies. Measures of TA do not provide predictive value in determining behavioral outcomes in the SSD population. Specifically, low TA does not suggest improved outcomes with a BAI.

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