Card Set Information
What is an ultrasound?
high frequency sound waves that can be converted to heat
mechanical vibrations produced by oscillatory molecules
What are the 3 aspects of sound?
1. source- something within has to be vibrating.
2. energy is transferred from the source in the form of longitudinal sound waves
3. sound must be detected by ear or instrument
What are sound waves?
longitudinal waves that are transmitted through almost any substance - solid, liquid, or gas
Do sound waves travel faster and lose less energy in liquids/solids, or air?
*ear to train tracks
What is loudness?
sensation of listner related to the energy in the sound wave
What depends on frequency and amplitude?
What is pitch?
sensation of listener to a high or low pitch
What depends on frequency?
What is the human audible range?
Above human hearing range is called what?
Below human hearing range is called what?
What are the 4 steps for conversion of the ultrasound?
1. pulse of US is emitted by a transducer
2. crystal in transducer expands and contracts
3. linear progagation of waves through the tissue (lining up)
4. US is reflected at the interface where the tissues meet -> causes friction -> which causes heat
What is the frequency of ultrasound?
1,000,000Hz - 3,000,000Hz
1MHz - 3MHz
What is a transducer?
head of US - electrical device that transforms an electrical pulse into mechanical vibrations
What is the Piezoelectric effect?
piezoelectric crystal - pressure from electrical current is exerted on the crystal in the US head
pressure results in mechanical vibrations
When is the only time sound waves are seen or felt?
when reflected under water
What does not transmit sound waves?
What may occur is US is on and the sound head is held in the air?
crystal will shatter
melt the cement in the unit
transducer head will get really hot
What are some coupling/medium agents used with US?