Transducers—Part 2

Thursday, October 19, 1:30 pm — 3:30 pm (Rm 1E12)

Chair:
Alexander Voishvillo, JBL/Harman Professional Solutions - Northridge, CA, USA

P10-1 Loudspeakers as Microphones for Infrasound—John Vanderkooy, University of Waterloo - Waterloo, ON, Canada
This paper shows that a sealed-box loudspeaker can be used as the sensor for a very high-performance infrasound microphone. Since the cone displacement essentially responds directly to infrasound pressure, the velocity-induced loudspeaker output must be electronically integrated to give a flat response. The undamped resonance peak of the loudspeaker is avoided by feeding the short-circuit voice coil current into the virtual ground input of an integrator op-amp. Design equations are given and a complete response analysis is presented. A prototype is compared with a conventional microphone used for infrasound measurement, showing the improved performance of the sealed-box loudspeaker design. 

P10-2 A Low-Cost, High-Quality MEMS Ambisonic Microphone—Gabriel Zalles, New York University - New York, NY, USA; Yigal Kamel, New York University - New York, NY, USA; Ian Anderson, New York University - New York, NY, USA; Ming Yang Lee, New York University - New York, NY, USA; Chris Neil, New York University - New York, NY, USA; Monique Henry, New York University - New York, NY, USA; Spencer Cappiello, New York University - New York, NY, USA; Charlie Mydlarz, New York University, CUSP - New York, NY, USA; Melody Baglione, New York University - New York, NY, USA; Agnieszka Roginska, New York University - New York, NY, USA
While public interest for technologies that produce and deliver immersive VR content has been growing the price point for these tools has remained relatively high. This paper presents a low-cost, high-quality first-order ambisonics (FOA) microphone based on low-noise microelectromechanical systems (MEMS). This paper details the design, fabrication, and testing of a MEMS FOA microphone including its frequency and directivity response. To facilitate high resolution directivity response measurements a low-cost, automatic rotating microphone mount using an Arduino was designed. The automatic control of this platform was integrated into an in-house acoustic measurement library built in MATLAB allowing the user to generate polar plots at resolutions down to 1.8°. Subjective assessments compared the FOA mic prototype to commercially available FOA solutions at higher price points. 

P10-3 Automated Auditory Monitoring Using Evoked Potentials and Consumer Headphones—Thomas Rouse, Plextek - Great Chesterford, Essex, UK; Loek Janssen, Plextek - Great Chesterford, UK
Auditory Evoked Potentials (AEP) are electrical signals resulting from activity in the auditory system in response to stimuli. The characteristic waveforms can be indicative of cochlea and auditory brainstem function and may change after the onset of tinnitus or hearing threshold shifts, whether permanent or temporary. AEP measurement is currently used by audiologists for hearing assessment in infants and to aid the diagnosis of some diseases. Measurements were made using a variety of consumer headphones and integrated electrodes and compared with a reference audiology system. The results showed the ability to record a consistent response and indicated that AEPs can be reliably measured outside a clinical environment. This could be used to automatically monitor for changes in a user's hearing. 

P10-4 A Digital Class D Audio Amplifier with Pulse Density Modulation and Distortion Suppression Feedback Loop—Robert McKenzie, University of Toronto - Toronto, ON, Canada; Xinchang Li, Graduate University of the Chinese Academy of Sciences - Beijing, China; Martin Snelgrove, Kapik Integration - Toronto, ON, Canada; Wai Tung Ng, University of Toronto - Toronto, ON, Canada
A novel fully digital Class D amplifier is presented in which the output stage error is digitized by a 10-bit ADC and fed back into the modulation path to suppress distortion. This technique attenuates the in-band noise introduced by the output stage, and can tolerate large latency. A fully digital Pulse Density Modulation (PDM) Class D amplifier with output stage noise shaping is implemented on a PCB prototype. Feedback loop functionality is verified experimentally, and a 10 dB improvement in Total Harmonic Distortion plus Noise (THD+N) is realized.