Sounds1.pdf PDF - Medical Physics Course Packet

Course Packet LM...

Course Packet LM01-FPHY 02 0425 Enhancement Activity: I. Copy and complete the following concept map on sound. Sounds II. Choose the word or phrase that best answers the questions. 1. A tone that is lower in pitch is lower in what characteristic? a. frequency c. loudness b. wavelength d. resonance 2. If the wave speed stays the same, which of the following decreases as the frequency increases? a. pitch c. loudness b. wavelength d. resonance 3. What part of the ear is damaged most eas- ily by continued exposure to loud noise? a. eardrum c. oval window b. stirrup d. hair cells 4.What is an echo? a. diffracted sound c. reflected sound Learning Module: Medical Physics 37  Course Packet LM01-FPHY 02 0425 b. resonating sound d. an overtone 5. A trumpeter depresses keys to make the column of air resonating in the trumpet shorter. Sounds What happens to the note being played? a. Its pitch is higher. c. it is more quiet b. its pitch is lower d. it is louder 6. When tuning a violin, a string is tightened. What happens to a note being played on the string? a. Its pitch is higher. c. it is more quiet b. Its pitch is lower d. it is louder 7. As air becomes warmer, how does the speed of sound in air change? a. It increases. C. it doesn’t change b. It decreases d. It oscillates. 8. Sound waves are which type of wave? a. slow c. compressional b. transverse d. electromagnetic 9. What does the middle ear do? a. focuses sound c. collects sound b. interprets sound d. transmits and amplifies sound 10. An ambulance siren speeds away from you. What happens to the pitch of the siren? a. It becomes softer. c. it decreases b. It becomes louder. d. it increases. Generalization: Sound Waves Sound waves are compressional waves produced by vibrations. Sound travels fastest in solids and slowest in gases. Sound travels faster as the temperature of the medium increases. The energy carried by a sound wave increases as its amplitude increases. Learning Module: Medical Physics 38  Course Packet LM01-FPHY 02 0425 Loudness and Pitch Loudness is the human perception of the energy carried by a sound wave. Sounds The pitch of a sound becomes higher as the frequency of the sound increases. The Doppler Effect and Diffraction In the Doppler effect, the frequency of a sound wave changes if the source of the sound is moving relative to the listener Diffraction occurs when sound waves bend around objects or spread out after passing trough an opening. Music Music is sound that is deliberately produced in a regular pattern. Objects vibrate at certain natural frequencies. The lowest frequency produced by a vibrating object is the objects fundamental frequency. The overtones produced by a vibrating object are multiples of the fundamental frequency. Musical Instruments and Hearing In stringed instruments the sounds made by vibrating stings are amplified by a resonator. Percussion instruments produce sound by vibrating when they are struck. Brass and woodwind instruments produce sound by vibrating a column of air. The ear collects sound waves, amplifies the sound, and interprets the sound. APPLICATION: The use of sound in medicine started since long time ago. Doctors have used stethoscopes to listen to human body’s internal sounds since the early 19th century and the ultrasound imaging has develop to a powerful device in obstetrics and other medical aspects that expectant mothers need to know the gender of their offspring by 20 weeks of development. Also it is used to examine some organs and blood flow and sound reflects at boundary of tissues with different densities. Learning Module: Medical Physics 39  Course Packet LM01-FPHY 02 0425 Sounds Today scientists are continuing to study and seek more advanced applications of sound in medicine. An acoustical energy can be concentrated used for imaging and curing a variety of ailments which includes cancer, stroke, and Parkinson's disease. Sound waves can be focused deep inside the body to manage hemorrhages or internal blood clothing, they can help to assist doctors in giving drugs to specific areas in tissues, and they can prevent adverse bacterial infections. Neurosurgeons use a device called a cavitron ultrasonic surgical aspirator (CUSA) to take away brain tumors once thought to be very difficult to operate. The probe breaks any section of the tumor that it fells and the remains are removed out of the brain with a saline solution. With the help of the tip of the probe which is small, the surgeon can selectively remove small bits of malignant tissue without destroying or damaging the surrounding healthy tissue. The Doppler flow meter is a plays an important part in medical application of the Doppler effect. This device gauges the speed and control of blood flow by transmitting and receiving elements that are placed directly on the skin. The transmitter release a continuous sound, when the sound is echoed from the red blood cells, its frequency is changed in a kind of Doppler effect because the cells are in motion. The receiving element senses the reflected sound, and an electronic counter calculates its frequency, which is Doppler-shifted relative to the transmitter frequency. The Doppler flow meter can be also used to set regions where blood vessels have narrowed since much flow speeds occur in the narrowed regions, according to some medical Learning Module: Medical Physics 40  Course Packet LM01-FPHY 02 0425 studies. Also, the Doppler flow meter can be used to sense the movement of a fetal heart as early as 8–10 weeks after formation. Sounds Ultrasonography (sonography) uses multiple acoustic transducers to convey pulses of sound into a material. When a sound wave came across with a material with a different density, a part of the sound wave is reflected back to the probe and is sensed as an echo. The duration it takes for the echo to move back to the probe is computed and used to calculate the depth of the tissue interface causing the echo. The higher the difference between acoustic impedances the larger the echo is. If the pulse strikes gases or solids the density difference is so much that most of the acoustic energy is reflected and it becomes impractical to see deeper. Videos to watch, here’s the link: https://www.youtube.com/watch?v=GKh2XFmsUx4 https://www.youtube.com/watch?v=7CdYUivqjLQ Reminder : Jot down notes on additional information and ideas from the video clips which are not presented in our lecture. Learning Module: Medical Physics 41