physics

2. 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.

3. Bats and ultrasonic sound waves
Bats use ultrasonic frequencies up to 100 kHz for locating their food sources
and navigating.

4. Infrasonics
Rhinoceroses use infrasonic frequencies as low as 5 Hz to call one
another.

5. 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.

6. 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

7. 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, doesn’t ionize atoms or break up molecular bonds.
It is safe to use in obstetrics.

8. Doppler Flow Meter
A Doppler flow meter measures the speed of red blood cells.

9. 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.

10. 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.