User's Manual

Chapter 6: Safety 79
Safety
Acoustic measurement precision and uncertainty
Alltableentrieshavebeenobtainedatthesameoperatingconditionsthatgiverisetothe
maximumindexvalueinthefirstcolumnofthetable. Measurementprecisionanduncertainty
forpower,pressure,intensity,andotherquantitiesthatareusedtoderivethevaluesinthe
acousticoutputtableareshown
inthetablebelow.InaccordancewithSection 6.4oftheOutput
DisplayStandard,thefollowingmeasurementprecisionanduncertaintyvaluesare
determinedbymakingrepeatmeasurementsandstatingthestandarddeviationasa
percentage.
d
eq
(z) Equivalent beam diameter as a function of axial distance z, and is equal to
, where I
TA
(z) is the temporal-average intensity as a
function of z in centimeters.
fc Center frequency in MHz.
Dim. of A
aprt
Active aperture dimensions for the azimuthal (x) and elevational (y) planes in
centimeters.
PD Pulse duration (microseconds) associated with the transmit pattern giving
rise to the reported value of MI.
PRF Pulse repetition frequency associated with the transmit pattern giving rise to
the reported value of MI in Hertz.
p
r
@PII
max
Peak rarefactional pressure at the point where the free-field, spatial-peak
pulse intensity integral is a maximum in Megapascals.
d
eq
@PII
max
Equivalent beam diameter at the point where the free-field, spatial-peak
pulse intensity integral is a maximum in centimeters.
FL Focal length, or azimuthal (x) and elevational (y) lengths, if different
measured in centimeters.
Table 14: Acoustic Output Terms and Definitions (Continued)
Ter m Definition
4 π()⁄()Wo()ITA z()()⁄()
Table 15: Acoustic Measurement Precision and Uncertainty
Quantity
Precision
(% of standard deviation)
Uncertainty
(95% confidence)
Pr 1.9% +
11.2%
Pr
.3
1.9% +12.2%
Wo 3.4% +
10%
fc 0.1% +
4.7%