David W. Clark

Ultrasound transducer assembly incorporating acoustic mirror

An ultrasound transducer assembly includes an acoustic mirror, an ultrasound transducer positioned to direct a scanned ultrasound beam at the acoustic mirror, wherein the scanned ultrasound beam is reflected by the acoustic mirror to form a reflected ultrasound beam, and an actuating device for moving the acoustic mirror relative to the scanned ultrasound beam so that the reflected ultrasound beam scans a three-dimensional volume. An ultrasound matching fluid may be disposed between the ultrasound transducer and the acoustic mirror. The actuating device may be configured for rotating the acoustic mirror, translating the acoustic mirror or rotating and translating the acoustic mirror. The acoustic mirror may have a single acoustically-reflecting surface of may be a polygon having a plurality of acoustically-reflective surfaces.

Detecting a relative level of an ultrasound imaging contrast agent

A method for detecting a relative level of a contrast agent in a region of a body, where the contrast agent is susceptible to destruction by a destructive ultrasound signal. The method comprises the steps of: determining a signal level from a first ultrasound echo that is produced in the region during a first time, which occurs while the contrast agent is present in the region; determining a signal level of a second ultrasound echo that is produced in the region during a second time, which occurs after destruction of the contrast agent; and determining a ratio of the signal level from the first ultrasound echo and the signal level from the second ultrasound echo, where the ratio indicates a relative level of the contrast agent during the second time as compared to the first time.

Loudspeaker drive‐unit measurements at excursion

Loudspeaker drive units are conventionally modeled as linear devices. Evidence is presented that shows that this assumption leads to unacceptable modeling errors for practical conditions of use. This paper presents new techniques for accurate, nondestructive measurement of linear and nonlinear electromechanical parameters. These parameters are used in more complete models which improve accuracy of frequency response and distortion estimates. The measurement workstation uses pneumatic pressure to displace the diaphragm in order for position‐dependent parameters to be measured over the full excursion range. Suspension compliance and mechanical damping are measured under conditions which simulate normal operation, thereby capturing the influence of creep, aerodynamic drag, and other second‐order characteristics which are not measured separately at present. Moving mass and force factor measurements utilize a magnetic position servo and gravity to obtain data without displacing the suspension. Conventionally, ...