Ultrasounds and why they are helpful to humans
EXTENDED ESSAY
Ultrasounds and why they are helpful to humans
Ivan La Bruna
D #0261-011
American School of Milan
IB Extended Essay
May 2003
Word Count: 3770
Abstract
Ultrasounds are sound waves that exceed the limit of human hearing. In latin ultrasound means that it goes beyond a boundary, in this case the sound wave goes over our hearing capacities. The study of sound waves could be considered ancient study because sound was always an interest of the people. This is why people created many musical instruments in different areas, the most curious thing is that the shapes differ from location and also produce different sounds. Without these studies on sound scientists or explorers probably would have not reached the level of wave reproduction there is in modern times. In the past sound waves were reproduced with wind and string instruments while in modern days scientists are able to create a sound wave with specific requirements.
What will be discussed in this essay will be an explanation on what aer ultrasounds and why they are applied to society. Ultrasounds are used mainly in the medical environment but also in detecting the distance of objects, on submarines, and other uses which will be discussed. The good thing about ultrasounds is that they are not very expensive and for this reason it has expanded more and more. For example ultrasounds are used in the medical world to scan the fetus in the womb of a woman, thanks to this equipment the doctors are able to control the fetuses health without harming the fetus and not making the client pay expensive bills. The positive aspect of ultrasounds is that by using a moderated frequency it does not harm the skin tissues of our body nor other organs, it is a safe method to image parts of our bodies without harming them, this is why it is used so often.
Ivan La Bruna
Table of Contents
Abstract
2
Background
4
Introduction
9
How it is produced
1
How it works
3
What is it used for
6
Conclusion
8
Bibliography
20
Background
Humans, as other living beings, have the capacity to hear and to listen what sorroundings them. With this ability, civilized humans, started to study sound and how it behaved. The study of sound could be considered one of the most antique studies existing, people have always curioused on how to produce new sounds. The voice was explored continuosly, people started in producing new sounds with their voice and changing the tone of it in order to produce different melodies, learning how to control their vocal cords. The reproduction of sound is a natural isntinct for humans, people noticed that by changing their voice they were able to transmit some information to another person such as anger or exitement. Humans are able to have a voice because our body developed vocal cords which vibrate at the rate that we decide, the more the speed of vibration of the cords are changed, the higher the pitch. The vibration of vocal cords then becomes our voice, and when the human race has evolved to modern times, they were able to have a form of communication called language which makes the communication between people much better. But once that the human race was able to have language they still continued their studies such as making instruments.
The exploration of sound is one of the areas that have interested people the most especially because they could make instruments that produce different sounds, the first instrument might be thought as the mouth because it was the first thing with which man was able to use to reproduce sound. People started to make different instruments because they understood how to reproduce sound. The most popular instruments were based on the air blown in them and by having strings vibrating. For example a guitar has six strings, each string will produce a different sound because of its vibration, the vibration gives the sound wave a specific speed. Considering that two strings are aside with same thickness but different length, if they are plucked in the same place then they shorter string will produce a higher pitch than the longer string. Manufacturing instruments brought people to actually pay attention to the vibration process and noticed that it was an important factor on the outcome sound but they never went in deeper technical study as modern days. The actual study of the speed of sound came much later in time, and only in modern days people were able to understand that what we heard was affected by the speed of sound and by the amplitude. People such as Daniel Colladen who attempted to calculate the speed of sound in water in 1822 was one of the first pioneers in ultrasounds without any great discovery. In 1880 Pierre Curie and Jacques Curie discovered that by applying pressure on a quartz crystal thus would generate an electrical impulse that would deform the crystal and vibrate at a very fast rate. The quartz would generate high sound frequencies or else called ultrasounds that couldn't be heard by the ear.1
People started to use ultrasounds for the benefit of people when, in 1912, the Titanic sank and killed a large amount of children and women because of an unwarned iceberg. Scientists immediately thought of creating a device that would prevent a disaster similar to the titanic incident, the device would have allowed ships to detect any dangers such as icebergs or any other floating menace on the ocean. In 1914, Reginald A. Fessenden built the first functional sonar which was also used by submarines in the First World War, thus would detect floating icebergs and also enemy submarines to attack them. The sonar was also called 'hydrophone', the problem with these early devices was that they only had the capacity to perceive signals and not to emanate nor send sound signals. 2
After the First World War scientists made another great development in ultrasound technology, an ultrasonic metal flaw detector was constructed which was used to detect the integrity of the materials in ships during the battles. Once that scientists and doctors notices that ultrasounds could be used for the benefit of the people, because parts of bodies could be mapped, scientists explored the new area creating new equipment and being pioneers in the field they were gaining a lot of information. By 1985 Japanese doctors had equipment that had real time mapping of the subject diagnosed seen in a ...
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After the First World War scientists made another great development in ultrasound technology, an ultrasonic metal flaw detector was constructed which was used to detect the integrity of the materials in ships during the battles. Once that scientists and doctors notices that ultrasounds could be used for the benefit of the people, because parts of bodies could be mapped, scientists explored the new area creating new equipment and being pioneers in the field they were gaining a lot of information. By 1985 Japanese doctors had equipment that had real time mapping of the subject diagnosed seen in a 3D image (Diagram1).
Diagram 1
3
During recent times ultrasound devices are used more in the medical area than any other, especially for the pregnancy of a woman (Diagram 2 and Diagram 3). With ultrasounds a doctor is able to observe a fetus without touching the baby, therefore, having less probabilityn of harming it. Modern studies, and the improvement of technology, brought the equipment to have color monitoring of what is observed and also a three dimensional image of it in order to see the fetus as it really is inside the womb of the woman at any pregnancy stage. Diagram 2 shows a scan done in the womb of a woman at an advanced growth stage of the fetus, the head is well formed and it seems that the fetus is having a laugh. With the ultrasound scan the image seen is clear and since it's real time, the doctors can notice its movements and the shape of the body.
Diagram 2
4
Face of a fetus, the nose, the mouth and the body are clearly seen. The fetus seems to laugh while being scanned.
Diagram 3
5
Profile of the head of a fetus
Ultrasounds were studied and analyzed for many years to completely understand how they worked in more depth, this brought scientists to progress in both science and technology (as the four pictures in Diagram 4 shows). Ultrasounds became very useful to society because of its functions and also because the equipment had very low costs. Ultrasounds were also studied beause they were able to be precise, harmless to the body, and especially not expensive which gives every person a chance to use this technology for their benefit.6
Diagram 4
1985 1990 1995
7
997
Introduction
Human beings through out its existence developed the sense of hearing with organs such as ears which gives them the capacity to hear whatever surrounds them, the capacity to hear was understood since the beginning of the world and used to benefit living. During humans evolution they noticed that they were able to use their mouth and ears to transmit and receive information between themselves, this information travelled in sound, a form of communication was being established; the mouth was used to transmit the data to another person, while the ear was used to receive the data that was being sent. The human body is limited in producing and also receiving sound signals, this limit was unknown to people in ancient times until studies were done just on sound. Scientists discovered that sound traveled through air at different rates or frequencies and that the human body could detect and create only a determined amount of these frequencies. It has been decided after many experiments that the range of human hearing is from about 10 Hz to 20,000 Hz 8. Since it is considered a range, this means that on an average the human ear cannot percieve any sounds below and above the defined range. What went beyond humans limit of hearing was decided by scientists to be called ultrasounds, this sound is not able to be heard from humans because it's frequency is too fast for our organs to detect it.
The word ultrasound was given to this event because the roots are: "ultra" which comes from the latin word ultra or ulter which essentially means to go beyond the limit; "sound" from latin word soner9. If it is used as a prefix in front of the word sound (ultra-sound) then it means that the sound goes beyond the limit, the limit in this case is the 20,000 Hz. Ultrasound is based on the human hearing system, if it was based on the animals hearing system then the range wouldn't be from 10 Hz - 20,000 Hz but it would be wider, some studies show that dogs have the range from 67 Hz - 45,000 Hz and cats from 45 Hz - 65,000 Hz which is impressive because they are able to hear almost more than twice as much frequency than humans10. When scientists were able to produce sound with frequency higher than 20,000 Hz whatever was produced was not initially identified as ultrasound but just sound at a high frequency. A term had to be given to that sound frequency, the first term thought was supersonic, then it changed into hypersonic waves, but most of them were rejected because they were used for other situations. Supersonic was reserved more for object or moment in which something exceeded the maximum velocity of sound., the term hypersonic was instead never used because the term Ultra sound was most "popular". Hypersonic is brought back only when discussed about waves reaching the frequency of 1GHz.11
Ultrasonic is defined as "the science and technology dealing with acoustic waves both elastic and stress"12. To be more precise: "Acoustics is the science of sound, including its production, transmission and reception."13. Since sound is the propagation of mechanical energy traveling into a material medium, the waves are most likely to contain data and information. The waves contain so much information that not all of it is wanted, most of it is what we call "noise" and it can interfere with the other sets of information that a wave can contain. With acoustics people are able to delete that part of "noise" and obtain clear and precise data, the "noise" obstructs and is also unnecessary, acoustics also gives a chance to scientists to study sound in all its depth14.
The way we hear depends by many factors, sex, age, and especially by the person itself on how he treats its ears. For example a disc jockey tend to lose a little bit of audibility due to the extended exposure of the ear to loud music in clubs and in his headphones; due to this dj sometimes have autite problems and have to wear ear plugs to heal the ear. It also depends on the pressure of the wave, sound waves have pressure and if the pressure is really high then our ear will have hard times to hear beacause it might be too strong for it.
How it is produced
Humans can produce sounds in many ways but the result is that the hearing system cannot capture sounds higher than approximately 20,000 Hz and so they are unaware of the other sounds that are created. To produce such a high frequency a technical equipment is needed, most cases transducers are used. A transducer is an acoustical signal processing unit15, there are mainly two types of transducers: the first one is a receiving transducer that detects signals and the second one is a transmitting transducer which sends signals out into space. A transducer may also be understood as having a system or array of devices which can contain more than one transducer. For example usually the devices that are used on the stomach of a woman to see the fetus are usually a transducer (Diagram 5), they are also called probes. These transducers are mainly composed by more than one piezo-electric device that has the capacity to send and receive sound signals.16 Depending on the intensity of the signal that is received and by the skin tissue the device will interpret the data and display an image, of what is being analysed, on the monitor17.
Diagram 5
8
There are four different types of transducers that send signals; electromagnetic, magnetostrictive, piezoelectric, and optical. All of them are efficient and give precise and accurate results. All of them have the same principle in having a magentic field create an electric field, except for the optical transducer which is based on light rather than magentism, but all of them are constructed differently depending on what a person wants to specifically.
The electromagnetic transducer is very simple and easy to understand how it works. When the pressure of the ultrasonic wave reaches the transducer, this will detect the wave and the wave will cause a magnet to move in a coil, the magnet by moving in the coil will then create an electric current due to magnetism. The magnetoscrictive works the same way as the electromagnetic transducer but it uses nickel that will change dimensions due to the motion of the magnetic field, by having this change in dimension it will then create electric current. The Piezoelectric transducer is probably the most used transducer, it uses the principle that certain materials such as quartz, crystals, and other polymers change their dimensions when an electric field is around them. The electric field will cause the polymers to vibrate with the result of having them produce an electric field as the one that was acted on it. The piezoelectric transducer both creates and retains a magnetic field. The optical transducer instead is divided into two categories: coherent and incoherent. The coherent optical transducer detects sound waves by a change of light energy. The incoherent optical transducer operates only when the light intensity is changed by sound pressure19.
How it works
It is very simple to understand how a transducer work because it works the same way as light and water waves. In order for a wave to be sent and travel in space to be received, three elements are fundamental: a source, a medium, and a receiver. Since it is a communication process it can be easily compared as language; for language in order to communicate something to someone a person who talks (source) is needed and a person who will listens (receiver) is also necessary. The medium in this case will be the type of communication, in other words it would be language. For sound waves it is almost the same concept, not exact but similar, an easy example is the sonar that is used in submarines. A source is needed to create the sound wave, it could be anything, from a person talking to a hammer being hammered against a wall or a transducer. The medium could vary depending on where the source is creating the waves, the importance for the medium is that it should be matter, in the submarines case it would be water. The receiver is what receives the information that the source is generating. So a submarine will have a transducer or more to transmit the signal to other submarines or towards an object, the sound wave will bounce back and will return to where it came from and the submarine will receive the signal, which has traveled through water, and be interpreted by software. Essentially these systems can be identified into two categories: the active mode or the passive mode20.
The active mode consists in having two transducers: one that receives and the other that transmits signals from the same system. The active mode is furthermore divided into two more types: the monostatic (Diagram 6) and the bistatic (Diagram 7). The monostatic active mode means that both the receiver and the sound source are on the same platform or in the same transducer, while the bistatic has the receiver and the sound source in the same system but separated. The importance of having an active mode is that the sound source could be under control of the listener21.
Diagram 6
Monostatic Active Mode
Diagram 7
Bistatic Active Mode
The passive mode instead is a system that has some disadvantages because the sound source is not controlled by the listener but vice-versa, the target that has under control the sound source. For example on a submarine the passive mode would be that only the submarine would send a signal towards a location where the receiver is, on an active mode there will be both the sound source and receiver on the submarine or from the opposite location22.
The passive and the active modes are used in most appliances. Recent studies have brought ultrasounds to be more effective, the mapping became much more detailed and some of them contain also color. Also the equipment became mobile and therefore it is not necessary to be in a room but can also be in a van or outside in a field23. The Acuson Corporation technology is giving a new area to discover to scientists. Acusons technology gave the sound wave certain characteristics. The sound wave according to Acuson Corporation24 contains two types of information within it, one of these is the amplitude of the wave, the other is the phase. These two characteristics make up the whole entire information of a sound wave. Based on these two pieces of information the mapping is done easily and the visualization of it is of good quality. The equipment they dispose makes them capable to make a real time map of the scanned area with a good color definition. With this mapping technique the skin tissues and the other parts of the body are identified much faster and the image is much clearer than others products. This technology is very very advanced making them very unique25.
What is it used for
Ultrasounds now days are used as radars in small controlled systems such as the tomography to keep under control the growth of a fetus in the womb of a woman. It is also used to test materials and their state of matter. With the ultrasounds pressure it is possible to use ultrasounds for medical cleaning such as in dentist laboratories in order to sterilize the tools they operate or work with. The ultrasound cleaning is also used for jewels and other objects.26 It is also used as a humidifier to get rid of the moisture and humidity in order to have a dry house in which people could breath better during the night.27
The most popular use of ultrasound is in the medical field, ultrasound is used in order to observe parts of the inner body with the use of sound waves refraction, for example to see when a baby is in the womb of a woman. Ultrasound are being used as movement detectors; it is set to detect a certain frequency, when this minimum frequency is exceeded the alarm will activate, it is very usefull as a home product against thiefs. New products come out everyday such as the sonic devastator which produces high frequencies that create great pain on people if pointed towards them. The usage is also extending towards the study of the heart. With the use of ultrasound technology doctors are able to detect the flow and motion of blood in a heart. The sound wave is able to penetrate without harming all the way to the heart, this discovery can help the study of the heart while its functioning in a body. It could be analyzed and experimented to see the effects or side effects of certain behaviors.28
Ultrasound is being used also in daily occasions, such as the police using it to detect the speed of a car. They have this little transducer that sends out the sound signal, whenever it reaches the car, this wave signal will return back to the transducer and it will calculate the distance and the amount of time in order to calculate then itself the speed of the car. The police car has to be careful to not change the speed of the car otherwise the data might be corrupted. Ultrasounds are also used in ground leveling, by using sound waves it is possible to detect the distance of an object with a specified software that interprets the data and analyses them. There are many other appliances and devices that use the properties of ultrasounds. The more scientists study them the more people will have appliances, on them. The good thing about ultrasounds is that they are really cheap and that it doesn't harm any tissue of our body.
Conclusion
The progress of Ultrasounds will continue only thanks to technologys progress because the more technology improves the more ultrasound technology will improve, both improvements are reciprocal to each other. Ultrasounds have more importance in the medical fields because it is observed that ultrasound waves do not harm the body tissues. Compared to x-rays ultrasonic mapping is getting much better and the quality is increasing exponentially. Also x-rays seem to map the most dense parts of the body rather than just the tissues, (Diagram 8 compared with Diagrams 1,2,4). There are no applications in curing people with ultrasounds now days. Doctors and scientists have still not found a way to use ultrasounds to cure diseases, for now it could only be helpful in the mapping environment, maybe in the future there will be some way to cure people, maybe by using the pressure property of ultrasounds. Which can become really strong since it can sterilize jewelry.
Diagram 8
29
X-ray image of a person chest, most of the bones are quite visible.
If ultrasound will continue to progress probably its use will increase since it does not harm the human body as others that don't such as chemotherapy, x-rays, and other methods of curing that have side effects in the long term. In fact ultrasounds are known to not have bad side effects to the body nor the skin, if really high frequencies are used then the body may resent the application of these frequencies. With the use of technology that is in fast progress, the equipment is not very expensive and this is a positive aspect especially in the medical field which gives a chance to many people to have use of the equipment. The more technology improves the more the equipment will be less expensive, in 1930 the ultrasonic devices were really expensive while in modern times most hospitals have equipment for fetus scanning. The usage of sound is becoming more frequent also in other areas, because the concept can be applied easily and also the equipment is very cheap in confront to other equipment, this is why it started to be helpful to humans. It was applied to society because it was not expensive and it's improvement was increasingly incrementing. If ultrasounds continue its progression then ultrasounds may be a new frontier of study that will bring the medical environment to improve to such a point that everything will be less expensive and be less harmful than other methods.
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Ivan La Bruna 0261-011