Today is Wednesday, Oct. 23, 2019

Laryngeal Biomechanics

Equipment used in our lab 

Flow Measurements

Particle Image Velocimetry | Our tomographic particle image velocimetry (tomo-PIV) system enables volumetric (3-D) velocity measurements. The tomo-PIV system is comprised of a light source that is synchronized with 4 high-speed video cameras. The light source is a high-repetition rate, dual cavity, Nd:YLF laser system (Litron Lasers, LDY304) with 30mJ output. The pulse rate of the laser can go up to 10kHz. The pulses from the laser are synchronized with 4 high-speed video camera (Vision Reseach, Phantom M340). The pulse width of the laser pulse is of the order of nano-second, which provides excellent spatial resolution in low Reynolds number flows. The high-speed video cameras can go up to 800Hz at full resolution (2560x1600). The synchronization of the high-speed laser and the high-speed video camera is done using a high-speed controller unit, which is made by LaVision GmbH. The cameras are also fitted with a 527 nm narrow band-pass filter. Davis® Software is used for post-processing of the tomo-PIV images to extract the volumetric velocity information, using a cross-correlation technique. The principle of the PIV method is based on measuring the particle displacement in the seeded flow between two light pulses. The light pulses illuminate the flow field with some known predetermined time interval. A digital camera then captures each illumination of the flow field in a separate frame. Each frame is divided into interrogation windows, which are cross-correlated between the two frames. The displacement of the particles inside the widow is determined from the highest (i.e. strongest) correlation peak from the cross-correlation function. Because the time interval between the two frames is known, each correlation window produces a velocity vector. The velocity field is obtained by applying interrogation windows (with some overlap) for the entire flow field. Advanced algorithms for PIV use adaptive shapes for the interrogation windows, which give high-fidelity flow vectors in large gradient flows (e.g. vortex). The tomo-PIV is an extension of the PIV technique and can measure the volumetric velocity based on the principle of tomographic volume reconstruction that is well known from magnetic resonance imaging (MRI). The 3D reconstruction of the volume velocity is made by tracing the particles motion within a 3D measurement volume from simultaneous images that are taken using 4 cameras. The tomo-PIV system can also be used to obtain data synchronized with an external event such as a send or receive a trigger from a sensor. For more information, click here.

Hotwire Anemometry | Hotwire anemometry (HWA) is used to measure the velocity of a fluid. The method is based on placing a hair-thin wire (or film) into the flow and quantifying the convective heat transfer between the wire and the flow. The wire is constantly heated and thus any changes in the flow conditions (i.e. its velocity, temperature, concentrations, etc.) will affect the heat transfer from the wire, which can be measured and quantified into some measurable engineering unit. HWA is a point-measuring technique appropriate for the measurement of time-series data in one-, two-, or three-dimensions in gas and liquid flows. HWA is particularly suitable for the measurement of flows with very fast fluctuations at a point (high turbulence) and the study of flow micro-structures, where there is a need to resolve small flow eddies down to the order of hundreds of microns. The lab is also equipped with a variety of single sensor films and probes. These include straight, 90 degree, and wedge-shaped probes with a quartz coating (0.5 or 2 micron meter). The sensors respond to frequencies up to 30 KHzFor more information, click here.

 

Acoustic Measurements

Microphones | Bruel and Kjaer. For more information, click here.

Sound Pressure Level meter | Larson Davis Model 831.  The meter provides both A and C frequency weighing. ‘A’ weighing is based on equal loudness contours where as ‘C’ weighing has a flatter response over much of the audio frequency band. The meter has a wide dynamic range (110dB) with both true rms and peak detection capability. The meter can stream time series data through remote serial interface, which is synchronized with the PIV measurements. For more information, click here.

Kay Pentax System | The Computerized Speech Lab (CSL) is an advanced speech analysis system. For more information, click here.

Glottal Enterprises Aeroview System | By recording oral (and nasal) airflow the system can calculated the glottal waveform using inverse filtering. For more information, click here.

Nasometer II (KayPENTAX, Model 6450) instrument and that allows for real-time measurements of nasality in the patient’s speech.  The system includes a Nasometer II module with a hand-held separator. For more information, click here.

 

Imaging

High speed cameras | FASTCAM SA5/SA4 and MIRO 340. For more information, click here or here.

Sheimpflug adapter | The Scheimpflug principle is a geometric rule that describes the orientation of the plane of focus of an optical system (such as a camera) when the lens plane is not parallel to the image plane. The adapter (seen here as the rectangular piece closest to the camera box) adjusts the images taken so they can be analyzed as straight on shots. For more information, click here.

 

Other Equipment

National Instrument PXI platform | for data acquisition, synchronization, and instrument control. The platform uses a PXIe-6672 card for the timing and synchronization using high-stability reference TCXO. The platform includes a PXIe-6356 card which enables measurement of 8 simultaneous analog inputs at 1.25 MS/s/ch with 16-bit resolution. The data acquisition card is used to collect data from EGG, pressure transducer, flow rate meter, and TTL signal from camera. The platform also includes a PXIe-4492 card, which is ideal for taking acoustic measurements using 8 simultaneously analog inputs at up to 204.8 kS/s with 24-bit resolution ADCs and 114 dB dynamic range. The microphone data is collected using the PXIe-4492. The control of the traverse systems, mass flow controllers, light source for the HSV camera is done from a PCI-6713 card for analog output control using 8 channels with 1 MS/s maximum update rate. The PXI platform interfaces with the other instrumentation in the lab through a NI-BNC 2010 which is a shielded connector block with signal labeled BNC connectors. For more information, click here.

Automated 3-axis traverse system |  Velmex Biaxial-slide system(s) for positioning in space the PIV camera and the VPI models. The biaxial-slide systems are ideal for fine motion adjustments of the traverse’s stage. These traverse systems are motorized and connected to a VXM motor controller, which allows for local and remote controlling of the motion of the axes. Traverse systems have an accuracy of 0.015% and a repeatability of 0.001% of their full range of motion. The traverse systems is remotely control using a LabVIEW programFor more information, click here.

Customized load cell |  was built in our lab to measure the elastic properties along the superior and inferior aspect of the vocal fold. The load cell is based on a full Wheatstone bridge configuration of strain gages bonded to the sensing element. The Wheatstone bridge provides a very sensitive electrical output signal as force is applied to the load cell. The load cell consisted of an arm (where the strain gages are attached) connected to a circular contact tip (1 mm diameter, 2 mm long) and is set to measure a 0–100 mN force range. The accuracy of the force measurements was within 0.3% of its full scale. For more information, click here.

Electroglottograph (EGG) | Used to investigate the vibratory characteristics of the vocal folds.  This non-invasive device provides a waveform representation of vocal fold dynamics and relative contact during phonation. For more information, click here.

Pressure Tranducers | Used to measure subglottal pressure or intraglottal pressure in a hemi-larynx model. For more information, click here or here.

Flow Seeders | Used to generate a polydisperse aerosol in high concentration for use as seed particles for PIV measurements. For more information, click here.

Computational Fluid Dynamics (CFD) solvers

The available commercial software programs that can be used for flow simulations include CFD++, ANSYS Fluent®, LS-DYNA, and TURBO. The data visualization is accomplished with large screen LCDs as well as polarized dual-projectors for 3D views using Tecplot, Matlab, OpenDX, Visual 3. Software programs are also available for different grid generation algorithms, such as Gambit-Fluent Inc. and Gridgen.

Sid Khosla, MD

Lab Researchers


Sid Khosla, MD
Assistant Professor of Otolaryngology
Director, University Voice and Swallowing Center
Co-Director, UC Voice Consortium
Phone: 513-558-5411
Email: khoslam@ucmail.uc.edu

Effie Gutmark, PhD
Distinguished Professor
Aerospace Engineering & Engineering Mechanics
Co-Director, UC Voice Consortium
Phone: 513-556-1227
Email: gutmarej@ucmail.uc.edu

Liran Oren, PhD
Research Assistant Professor
Phone: 513-558-0073
Email: liran.oren@uc.edu