title: A waveguide pulse-echo system for ultrasonic absorption measurements in biological media.
abstract: The system described has been designed for measurements of ultrasonic absorption in suspensions of biological cells. A novel feature of the design is the provision of a wave-guide sample tube which prevents beam diffraction. This ensures that the ultrasonic energy is wholly constrained between a single transducer and a moveable air-backed reflector, and is lost only by absorption in the sample. The associated electronics comprises a simple ultrasonic generator with variable power output, carrier frequency and mark-space ratio, and a digital thermometer with a thermistor probe for measuring the sample temperature.
mesh_terms: D000042:Absorption; D002477:Cells; D013535:Suspensions; D014465:Ultrasonics / Q000295:instrumentation*
chemical_list: D013535:Suspensions