User guide
164
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.
z
sp
For MI, the axial distance at which p
r.3
is measured. For TIB, the axial
distance at which TIB is a global maximum (for example, z
sp
= z
b.3
) in
centimeters.
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 40: Acoustic Output Terms and Definitions (continued)
Term Definition
4 WoITA z