Thanx Bob.... but... what music will drive him crazy???

Abba at ultra sonic???

CM

"Bob Crantz" wrote in message
nk.net...
It's all pure crap.

***************************************



Attenuation


Most engineers and scientists working in the ultrasound characterize
attenuation as the "half-value layer," or the "half-power distance." These
terms refer to the distance that ultrasound will travel in a particular
tissue before its amplitude or energy is attenuated to half its original
value.





Attenuation


Divergence of the wavefront

Elastic reflection of wave energy

Elastic scattering of wave energy

Absorption of wave energy





Ultrasound Attenuation


Material Half-power distance (cm)

Water 380

Blood 15

Soft tissue 5 to 1

except muscle 1 to 0.6

Bone 0.7 to 0.2

Air 0.08

Lung 0.05





Attenuation in Tissue


Ultrasound energy can travel in water 380 cm before its power decreases to
half of its original value.

Attenuation is greater in soft tissue, and even greater in muscle.

Thus, a thick muscled chest wall will offer a significant obstacle to the
transmission of ultrasound.





Attenuation in Tissue


Non-muscle tissue such as fat does not attenuate acoustic energy as much.

The halfpower distance for bone is still less than muscle, which explains
why bone is such a barrier to ultrasound.

Air and lung tissue have extremely short half-power distances and
represent severe obstacles to the transmission of acoustic energy.





Attenuation


As a general rule, the attenuation coefficient is doubled when the
frequency is doubled.





Beam Forming


Ultrasound beam can be shaped with lenses

Ultrasound transducers (and other antennae) emit energy in three fields

Near field (Fresnel region)

Focused field

Far field (Fraunhofer region)





Diagnostic scanning modes


Usually pulse-echo mode

Further classification depends on how information is displayed






A mode


Amplitude of pressure wave displayed with regard to position


Thickness of cornea





B mode


Amplitudes are represented as pixels (images)

Brightness of pixels - signal strength (Brightness mode)

256 brightness levels/256 gray scales






Shift beam after each transmission to get 2D image





M mode


M (motion) mode

Beam held in fixed position

Measure very fast motions

Heart valves



*******************

Here's typically ultrasound numbers:

In .08cm the ultrasound in air is 1/2 power. It looses 1/2 power every
.031 inches or 25 dB per foot due to spreading. The claims Joe pointed out
nearly match RB's claims about his boat or stereo.

Glory!