A compact retarding-potential Mott polarimeter is described that employs a thorium target. When operating at an electron accelerating voltage of 25 kV, the instrument provides effective asymmetry (Sherman) functions Seff between −0.15 and −0.25, the exact value being determined by the inelastic energy loss window selected. The corresponding scattering efficiencies I/I0 are in the range ∼6–2×10−3 resulting in optimized efficiencies η (≡S2effI/I0) of ∼1.6×10−4. These efficiencies are much larger than have been obtained previously with similar analyzers. The instrument is simple to construct, is stable in operation, and has a large electron-optical acceptance, estimated to be ∼104 mm2 sr eV. It is fully UHV compatible and is suitable for application in a wide range of spin-dependent studies.

Very low power electromagnetic (EM) wave sensors are being used to measure speech articulator motions as speech is produced. Glottal tissue oscillations, jaw, tongue, soft palate, and other organs have been measured. Previously, microwave imaging (e.g., using radar sensors) appears not to have been considered for such monitoring. Glottal tissue movements detected by radar sensors correlate well with those obtained by established laboratory techniques, and have used to estimate a voiced excitation function for speech processing applications. The noninvasive access, coupled with the small size, low power, and high resolution of these new sensors, permit promising research and development applications in speech production, communication disorders, speech recognition and related topics.

Recent experiments using a portable, extremely low-power electromagnetic motion sensor to detect the motion of the posterior tracheal wall during speech production will be presented. The motion of the wall may be related to the driving subglottal pressure through a lumped element circuit model, leading to an approximation to the voiced excitation function of the human vocal tract. Using the excitation and the recorded spoken audio, a stable and accurate transfer function of the vocal tract may be calculated every few glottal cycles in near real-time. The excitation function may be used to calculate very accurate pitch information at low cost, and the transfer functions may be employed as an additional feature vector to enhance the performance of a new class of speech recognizers and synthesizers. [Work supported by NSF and DOE.]

Low Power EM radar-like sensors have made it possible to measure properties of the human speech production system in real-time, without acoustic interference. This greatly enhances the quality and quantify of information for many speech related applications. See Holzrichter, Bumett, Ng, and Lea, J. Acoustic. Soc. Am. 103 ( I ) 622 (1998). By using combined Glottal-EMSensor-and Acoustic-signals, segments of voiced, unvoiced, and no-speech can be reliably defined. Real-time de-noising filters can be constructed to remove noise from the users corresponding speech signal.

Newly developed glottographic sensors, utilizing high-frequency propagating electromagnetic waves, were compared to a well-established electroglottographic device. The comparison was made on four male subjects under different phonation conditions, including three levels of vocal fold adduction (normal, breathy, and pressed), three different registers (falsetto, chest, and fry), and two different pitches. Agreement between the sensors was always found for the glottal closure event, but for the general wave shape the agreement was better for falsetto and breathy voice than for pressed voice and vocal fry. Differences are attributed to the field patterns of the devices. Whereas the electroglottographic device can operate only in a conduction mode, the electromagnetic device can operate in either the forward scattering (diffraction) mode or in the backward scattering (reflection) mode. Results of our tests favor the diffraction mode because a more favorable angle imposed on receiving the scattered (reflected) signal did not improve the signal strength. Several observations are made on the uses of the electromagnetic sensors for operation without skin contact and possibly in an array configuration for improved spatial resolution within the glottis.