3. The Frequency of a Sound
Wave
Audible Range: 20 Hz ----- 20,000 Hz.
Infrasonic waves: Sound waves with frequencies < 20 Hz.
Ultrasonic waves:
Sound waves with frequencies > 20,000 Hz.
4. Bats and ultrasonic sound waves
Bats use ultrasonic frequencies up to 100 kHz for locating their food sources
and navigating.
6. Piezoelectric Transducer
Piezoelectric transducer is used to produce and detect Ultrasonic Waves.
It is a quarts crystal which converts electrical oscillations into mechanical
vibrations (sound) and vice versa.
7. Applications of Ultrasound in
Medicine
1. Ultrasonic Scanner
2. The cavitron ultrasonic surgical aspirator (CUSA)
3. Bloodless surgery: High-intensity focused ultrasound (HIFU)
4. The Doppler flow meter
8. Ultrasonic Scanner
Ultrasound reflects from boundaries between two different media. Ultrasound
can be used to identify a wide range of soft tissues, whereas X-rays are useful
primarily in seeing hard tissue, such as bones.
Ultrasound is non-ionizing, doesnโt ionize atoms or break up molecular bonds.
It is safe to use in obstetrics.
9. The cavitron ultrasonic surgical
aspirator (CUSA)
Neurosurgeons use a cavitron ultrasonic surgical aspirator (CUSA) to โcut
outโ brain tumors without adversely affecting the surrounding healthy tissue.
10. Bloodless surgery
High-intensity focused
ultrasound (HIFU)
Another application of ultrasound is in a new type of bloodless surgery,
which can eliminate abnormal cells, such as those in benign hyperplasia
of the prostate gland.
This technique is known as HIFU (high-intensity focused ultrasound). It is
analogous to focusing the sunโs electromagnetic waves by using a
magnifying glass and producing a small region where the energy carried
by the waves can cause localized heating. Ultrasonic waves can be used
in a similar fashion.
The waves enter directly through the skin and come into focus inside the
body over a region that is sufficiently well defined to be surgically useful.
Within this region the energy of the waves causes localized heating,
leading to a temperature of about 56 ยฐC (normal body temperature is
37 ยฐC), which is sufficient to kill abnormal cells. The killed cells are
eventually removed by the bodyโs natural processes.
12. Research Articles
Compressibility of gastrointestinal tract tumors during
transabdominal sonographic examination: A clue to the
diagnosis of gastrointestinal lymphoma (p 59-62)
Yasutomo Fujii, Nobuyuki Taniguchi, Harumi Koibuchi,
Yoshikazu Yasuda, Hideo Nagai
Published Online: Jul 30 2007 3:37PM
DOI: 10.1002/jcu.20393
Sonographic examination of the appendix in acute infectious enteritis and
acute appendicitis (p 63-66)
Koichi Yabunaka, Toshizo Katsuda, Shigeru Sanada, Hidetoshi Yatake, Tsunemasa
Fukutomi
Published Online: Jul 27 2007 2:02PM
DOI: 10.1002/jcu.20394
Ductus venosus blood flow resistance and congenital heart defects in the
second trimester (p 72-78)
Jeng Hsiu Hung, Chong Yau Fu, Jen-Her Lu, Chia-Yi Selena Hung
Published Online: Aug 3 2007 1:45PM
DOI: 10.1002/jcu.20406
13. 2.9 Infrasonics
Infrasonics refers to waves whose frequencies lie below the audible frequency range.
Earthquake waves are infrasonic waves. There are 3 types of earthquake waves:
S-wave: A transverse body wave, can only propagate in solid rock.
P-wave: A longitudinal body wave, propagates at the speed of sound, and has a very
large range.
L-wave: The wave that forms along a boundary between two mediums such as air
and ground and is responsible for the immense damage that can occur in large
earthquakes.
A variety of animals and birds are sensitive to infrasonic waves. Many zoologists
believe that the sensitivity of such animals as elephants or cattle could provide them
with an early warning of earthquakes and weather disturbances.
14. Motion Sickness
For vibration at very low frequencies, motion sickness of people in boats must
have been one of the earliest noticeable effects. The human body is particularly
sensitive to vibrations and infrasound near 7 Hz, at which frequency there is an
overall mechanical resonance of organs in the abdominal and chest cavities.
From:
http://www.answers.com/topic/infrasound?cat=technology
