Determination of acoustic power outputs in the microwatt-milliwatt range

Ultrasonic absorption and attenuation in mammalian tissues

“…Here it is seen that the ratio of attenuation to absorption does not vary appreciably among these tissues, excepting testis, suggesting that tissue macrostructure and/or tissue constituents have little to ~1o with this diversity found in the measured loss coefficient. Attenuation measurements in testis (Frizzell et al 1977) were made using a phase insensitive, frequency independent radiation pressure technique, a primary method for the measurement of the second order quantities of intensity and power (Lele, 1962;Kossoff, 1965;Hill, 1970;Rooney, 1973;O'Brien, 1978). Thus, these values are much less susceptible to errors due to the phase cancellation artifacts described by Marcus and Carstensen (1975), who compared a piezoelectric receiver (phase-sensitive) with a radiation-force receiver (phase- (Frizzell, 1975) assuming linear frequency dependence insensitive), and also by Busse et al (1977), who compared the piezoelectric receiver with an acoustic-electric receiver.…”

Interlaboratory Acoustic Power Measurement

“…As already noted, the planar scanning technique requires absolutely calibrated hydrophone probes, whereas radiation force measurements may require the use of precision microbalances and careful customization of the measurement arrangement. 7,14,16 The preferred method depends mainly on convenience and the experience of the user. The long data acquisition time with the planar scanning technique restricts its use to measurements at lower frequencies.…”

“…1,4,5,11,13,14 To offer some insight into the procedures used in this work, a short description of these techniques is given in the following sections. Planar Scanning Technique The details of the planar scanning technique using a source of known power output such as the NIST transducer have been published previously.…”

“…Although the principle of the radiation force balance is simple and requires only accurate measurements of the static force produced by the ultrasonic energy, the implementation of the device is fairly complex. 14 In practice, careful customizing of the design is often required.…”

“…As already noted, radiation force balances applicable for diagnostic equipment characterization usually require a customized design and use precision commercial balances or microbalances (such as the Cahn 25/270 [Thermo Cahn, Madison, WI; www.cahn.com] and Mettler AT 250 [MettlerToledo, Inc, Columbus, OH; www.mt.com] balances) to "weigh" acoustic energy. 7,14 Often, specially designed absorbing materials are used as targets, such as a new acoustic absorber made of polyurethane polymer. 15 …”