Rob Adamson Assistant Professor My research concerns how sound is transformed from vibrations to perception, how this process can go wrong and what we can do about it.  I am engaged in several research projects on various hearing-related topics. I am currently looking for new students at both the MSc and PhD levels.  Skills that I'm looking for include a background in optics, hearing sciences, electronics, mechanics, physiology and/or computer programming. Send me an email with your CV and transcript to apply.

This is me next to our very cool 3D laser Doppler vibrometer, the Polytech PS400-3D.

Optical Coherence Tomography of the Ear

Optical coherence tomography is a relatively new imaging technique that uses a low-coherence interferometer to produce depth-resolved scans in tissue.  I am currently building both free-space and endoscopic OCT systems for imaging the ear.  The free-space system will allow us to look into the middle ear through the tympanic membrane and the endoscopic system will look through the round window into the cochlea.  To the right is an example of where we are heading: an image of a cadaveric tympanic membrane taken with an opthalmic OCT scanner.

High-frequency Ultrasound in the Human Auditory System

In collaboration with Jeremy Brown I have been working on a variety of  ultrasound-related technologies for use in the human ear.  High-frequency ultrasound is similar to conventional ultrasound but works at 20-70 MHz instead of the 1-10MHz range of standard ultrasound.  Our group is one of the first to try applying it in imaging the auditory system, resulting in some beautiful in-vitro images of different parts of the middle and inner ear.  We are currently working on using ultrasound as a drug-delivery system for the inner ear, novel approaches to high-frequency beamforming and opto-acoustic techniques in ultrasound. We are also looking at how to use new relaxor-PT piezoelectric materials to push the frequency and resolution of ultrasound imaging beyond what can be achieved with PZT.

Vibration analysis of the human skull

Bone conducted hearing aids are an effective way of treating conductive hearing loss, but the physiology of bone conduction has not received much study.  In a series of Laser Doppler Vibrometry experiments we have completely mapped the 3D vibrational response of a dry human skull to an applied point force.  As you can see in the videos below, there are three main regimes of vibration -- quasi-rigid motion below 1000Hz, modal vibrations between 1000 and 10,000Hz and standing waves above 10,000Hz
At 16,000 Hz clear wavelike motion can be seen.  The waves interfere to form a characteristic egg carton-like surface in the video above, but if we look only at motion in the x-direction, clear peaks and troughs are visible.  The waves have all of the properties of plate bending waves. With MSc student Carmen McKnight I am trying to understand the dispersion relationship for waves in the skull and using this data to establish a better model of how sound propagates in the skull

Powering implanted devices with ultrasound

Currently all active implanted hearing devices like cochlear implants are powered using a  pair of coils.   A current is driven in the outer coil and the changing magnetic field in the implanted coil generates an electromotive force that can drive the device.  In order to be efficient such coils need to be quite large, typically 5 cm in diameter. We are looking into using ultrasound as an alternative means of delivering energy to implanted devices.  Unlike magnetic fields, ultrasound can generated as a focused beam, and a large amount of energy can be concentrated in a small area.  Our devices are only 5 mm in diameter and yet can deliver over 400 mW of power to implanted devices with efficiency comparable to that of a 5 cm coil.

Hearing and balance aids

I have built a number of medical devices that we test on patients in Dr. Bance's clinic.  These range from balance aids to help patients with vestibular loss to localization aids to help patients with single-sided deafness to identify the locations of sound sources.   The hollow external ear transducer (HEET) is a novel bone conduction hearing aid that fits in the ear canal and vibrates the boney canal wall. The subcutaneous piezoelectric anchored hearing aid (SPAHA) is an impanted hearing aid that lies flat against the skull unlike the percutaneous BAHA.  This allows skin to heal over the implant which is both more cosmetic and less prone to infection. The balance belt is an aid for patients with vestibular loss.  An accelerometer constantly measures posture and provides feedback through vibrating motors located around the belt.

Journal Publications

Biomedical

RBA Adamson, M Bance and J A Brown, A piezoelectric bone-conduction bending hearing actuator, The Journal of the Acoustical Society of America, vol 128, no 4, pp 2003-2008, 2010

Z Torbatian, R Adamson, M Bance and J Brown, A split-aperture transmit beamforming technique with phase coherence grating lobe suppression, Ultrasonics, Ferroelectrics and Frequency Control, IEEE Transactions on, Vol 57(11), pp 2588-2595, Nov 2010

R Deas, R Adamson, L Curran, F Makki, M Bance and J Brown, Audiometric thresholds measured with single and dual BAHA transducers: The effect of phase inversion", Int J Audiol, 49, pp 933-9, Dec 2010

Brown JA, Torbatian Z, Adamson RB, Van Wijhe R, Pennings RJ, Lockwood GR, Bance ML, High-Frequency Ex vivo Ultrasound Imaging of the Auditory System, Ultrasound in Medicine and Biology 2009 Aug 11

Quantum Optics

(Before staring my post-doc I was a hard-core quantum physics researcher)

RBA Adamson and AM Steinberg, Improving quantum state estimation with mutually unbiased bases, Phys Rev Lett, vol 105(3), pp 030406, 2010

L. K. Shalm, R. B. A. Adamson and A.M. Steinberg, Squeezing and over-squeezing of triphotons, Nature 457, 67-70 (01 Jan 2009)

R. B. A. Adamson, P. S. Turner and A.M. Steinberg, Detecting hidden differences via permutation symmetries, Phys. Rev. A 78, 033832 (2008)

R. B. A. Adamson, L. K. Shalm, M. W. Mitchell, and A. M. Steinberg, Multiparticle State Tomography: Hidden Differences, Phys. Rev. Lett. 98, 043601 (2007)

R. B. A. Adamson, L. K. Shalm, and A. M. Steinberg, Preparation of pure and mixed polarization qubits and the direct measurement of figures of merit, Phys. Rev. A 75, 012104 (2007)

M.A. Touzel, R. B. Adamson, and A. M. Steinberg, Optimal bounded-error strategies for projective measurements in nonorthogonal-state discrimination, Phys. Rev. A 76, 062314 (2007)