Sunil Puria

Objectives/Hypothesis: The performance of an ossicular replacement prosthesis (ORP) is influenced by its alignment and appropriate tension between the tympanic membrane and the stapes footplate. A novel ORP with a flexible element that potentially allows for length adjustment in situ is presented and tested for acoustic performance.Study Design: Laser Doppler vibrometry in fresh human cadaveric temporal bones was used to test the acoustic performance of the adjustable ORP relative to standard prostheses used for ossiculoplasty.Methods: The three‐dimensional (3D) velocity of the stapes posterior crus was measured in the 0.2‐ to 20‐kHz range using a Polytec CLV‐3D laser Doppler vibrometer. The middle ear cavity was accessed through a facial recess approach. After measuring the normal response, the incus was removed and stapes velocity was measured in the disarticulated case, then after insertion of the new prosthesis, a conventional prosthesis (Kurz BELL Dusseldorf type), and a sculpted autologous incus prosthesis in each temporal bone. The 3D stapes velocity transfer function (SVTF) was calculated for each case and compared.Results: The novel ORP design restored stapes velocity to within 6 dB (on average) of the intact response. No significant differences in 3D‐SVTF were found between the new, conventional, or autologous ORPs.Conclusions: The inclusion of an in situ adjustable element into the ORP design did not adversely affect its acoustic performance. The adjustable element may increase the ease of achieving optimal ORP placement, especially through a facial recess approach.Level of Evidence: NA Laryngoscope, 126:2559–2564, 2016

Since the discovery of otoacoustic emissions and outer hair cell (OHC) motility, the fundamental question of whether the cochlea produces mechanical power remains controversial. In the present work, direct calculations are performed on power loss due to fluid viscosity and power generated by the OHCs. A three-dimensional box model of the mouse cochlea is used with a feed-forward/feed-backward approximation representing the organ of Corti cytoarchitecture. The model is fit to in vivo basilar membrane motion with one free parameter for the OHCs. The calculations predict that the total power output from the three rows of OHCs can be over three orders of magnitude greater than the acoustic input power at 10 dB sound pressure level (SPL). While previous work shows that the power gain, or the negative damping, diminishes with intensity, we show explicitly based on our model that OHC power output increases and saturates with SPL. The total OHC power output is about 2 pW at 80 dB SPL, with a maximum of about 10 fW per OHC.

Fully implantable hearing devices (FIHDs) have been developed as a new technology to overcome the disadvantages of conventional acoustic hearing aids. The implantable microphones currently used in FIHDs, however, have difficulty achieving high sensitivity to environmental sounds, low sensitivity to body noise, and ease of implantation. In general, implantable microphones may be placed under the skin in the temporal bone region of the skull. In this situation, body noise picked up during mastication and touching can be significant, and the layer of skin and hair can both attenuate and distort sounds. The new approach presently proposed is a microphone implanted at the tympanic membrane. This method increases the microphone’s sensitivity by utilizing the pinna’s directionally dependent sound collection capabilities and the natural resonances of the ear canal. The sensitivity and insertion loss of this microphone were measured in human cadaveric specimens in the 0.1 to 16 kHz frequency range. In addition, the maximum stable gain due to feedback between the trans-tympanic microphone and a round-window-drive transducer, was measured. The results confirmed in situ high-performance capabilities of the proposed trans-tympanic microphone.