Using my physics, I am able to develop my experiment from using a CD player to using a loudspeaker as I am aware that using a CD player radio, would not produce a constant sound frequency because the different pitch amplified represents different signals produced, therefore I shall use the sound generator connected to the loudspeaker to produce the constant sound. Therefore this experiment had progressed when I had changed using the CD player to the loudspeaker and sound generator. Moreover, I deem that when carrying out the experiment polystyrene would be the best insulator of sound, as when the atoms will not be able to penetrate due to the molecules which are along side each other which will collide and therefore this will retain sound the most, due to its structure. Related experiments to this particular one, is where I firstly was going to investigate sound insulation using only one layer of insulation for each material, and monitoring the effect of this. However, I found that increasing the number of layers would make this experiment more interesting. I was also going to investigate different thickness of insulation; however I was unable to carry this further as I was unable to get hold of the different material thicknesses. However I developed my experiment from investigating sound insulation of one layer to many layers which had made this more interesting. Using my knowledge, this was again developed to replacing the CD player, with sound generator connected to the loudspeaker which produced the constant sound waves.
I deem that my practical knowledge and skill are put to good in this experiment as I had to figure out, how I could carry out this experiment in a safe and clear way, which would bring me the most accurate results. My practical knowledge had came into use where I had used my resources such as the decibel meter in many ways, as I had made sure there was a constant measurement when not using the sound generator, and then applying this when needing to measure the sound. I used the same principle, with my ruler, as I had measured the layers length and width which needed to be cut out, and I had also measured out the set distance each time where I placed the decibel meter. I put my skill in this experiment, where I carefully had constructed the cardboard box so it was air tight, and had also carefully attached each insulating layer to another using cello tape ensuring that no damage was caused. Further, I perceive I had used my skill to the full extent, when measuring the amount of sound produced, ensuring the CD player was kept in the centre of the cardboard box, through marking out.
My experimental design consists of a sound generator located along the cardboard box, and in the centre of the cardboard box the loudspeaker. I would connect the loudspeaker via crocodile clips by piercing a sharp hole in the box and attaching this to the sound generator 10 cm apart along side the cardboard box I had placed the decibel meter. My experiment setup had consisted of very little apparatus; however I believe I had created a clear setup. I had designed this experiment so that I could easily investigate what material is the best insulator of sound using apparatus which will distinctly produce this information, as the decibel meter which is a sophisticated apparatus I believe can instantly under the conditions tell me accurate results of each material I place into the cardboard box with the set sound frequency.
I would deal with the effects with the effects by making sure that there is no sound in the room, and I would achieve this by closing all doors and making sure I am the only person present to carry out this experiment. Another effect, is when using a different decibel meter as this may have a different deflection, so I would overcome this by using the same apparatus all the way through by completing this on the same day so that there are no errors in my results. Further, another effect, which might affect the results are temperature as this can affect the path at which the sound travels at, to completely keep this constant I had kept a thermometer to ensure that there was no rapid increase in room temperature. Finally, another effect was the accuracy to which I had taken the results, as I had to make sure that when taking the reading from the decibel meter, I had made sure I had taken it to the nearest unit so that I would achieve accurate results. I achieved this by simply rounding off.
PHYSICS
In this experiment I will be using the four materials in turn to see how good of a sound insulator each one is. Here is the physics involved with each of the materials I will be using explaining why and how much of a good insulator it will be.
What is sound? A sound wave is a which travels through a medium by means of particle interaction. As one particle becomes disturbed, it exerts a force on the next adjacent particle, thus disturbing that particle from rest and transporting the energy through the medium.
Polystyrene: Polystyrene is a strong plastic created from acetylene and benzine that can be injected, extruded or blow moulded, making it a very useful and versatile manufacturing material. Most of us recognize Styrofoam a form of foam polystyrene packaging. Polystyrene is also used as a building material, with electrical appliances (light switches and plates), and in other household items. It is used in walls when it traps air due to the cavity wall which traps the sound in the small holes in which this material contains. Polystyrene foam is a product for the absorption, diffusion and isolation of sound to offset sound and acoustical problems. Very low conductivity gases trapped in the closed cell structure also reduce heat transfer by conduction, thereby further increasing the thermal efficiency of these foams. The small cell size practically eliminates convection, another source of energy transfer. It is moisture resistant, dimensionally stable, air tight, resistant to the transfer of heat through the building envelope, and has the ability to perform a structural role.
Polystyrene is a polymer. Polymers are long molecules with lots of atoms joined to one another like links in a chain. The diagram above shows one link in the chain, and the brackets with ‘n’ shows that it is part of an infinite number of links which are joined together.
Each molecule is composed of a string of carbon atoms joined by covalent bonds. Other atoms join on to the carbon atoms, but each carbon atom is always linked to two other carbon atoms. Covalent bonds are very strong and there is a large amount in a piece of polystyrene. This means that polystyrene is strong and durable because it takes a large amount of energy to break the covalent bonds.
The polystyrene has benzine rings attached to the carbon atoms of the polymer chain. The rings prevent molecules sliding past each other. This proves by increasing the stiffness of the polymer. Benzine rings are also very stable which proves to increase the strength of the bonds within polystyrene molecules.
The monomer 'styrene' is made into 'polystyrene' in a process called free radical vinyl polymerization. This is illustrated in the diagram below.
Polystyrene will absorb the sound waves, because of its softness and flexibility, which will enable the sound not to travel through fully. This is due to the structure of the polymer as the molecules which make up this, are very close together, therefore this means the sound waves will not be able to easily travel through the material. As the layers are added on to the existing layer right up to the third layer I deem that the amount of sound will vastly decrease each time, as the sound will become more and more insulated due to the amount of close molecules which will add up to form a wall will would not let much of the sound particles to travel right through. The amount of molecules will increase as the layers are added therefore the amount of sound detected will decrease. Here is a diagram which illustrates this:
I believe that Polystyrene is going to be the best insulator of sound as its molecules are extremely close and also because it is a superb insulator of both sound and heat.
Polythene:
Looking at my next insulating material which I will be using which is polythene, I deem that this is another polymer which has similar properties to polystyrene; however this material has much thinner walls of molecules, therefore more sound waves will be able to find there way through as this material would be less dense then polystyrene. This is illustrated in a diagram:
Polyethene is a polymer produced by reacting oxygen and ethene, in this reaction the small ethene molecules attach together to form long chain polymer molecules. Polyethene is a thermoplastic material which is often described as wax-like it is extremely tough and is has an excellent chemical resistance. It is also less dense than water and is the simplest polymer, these attributes lead to polythene being an extremely useful substance. Ethene (C2H4), is a simple hydrocarbon molecule which consists of 2 carbon atoms and 4 hydrogen atoms. Polyethene is simply a set of ethene molecules bonded together to form a chain, these chains can often stretch up to many times longer than the original ethene molecule. Below is a diagram of polyethene: Although normally ethene monomers have little attraction for one another, yet the polyethene molecules have a strong attraction for one another. Therefore I deem that as the layers are simply added the amount of sound detected would reduce, however this polythene would not be the best insulator out of the four, I believe it may be the least best due to its properties of being less dense and being extremely thin.
Bubble wrap:
Bubble wrap is a superb insulator of heat due to the air bubbles which hold the air in like a cavity wall. This prevents heat from escaping and in the same way will prevent the sound escaping by insulating it. However the bubble wrap I am using does not consists of the silver foil in each side, as this is what would be a better sound insulator, but due to my experiment I do not want to make any amendments to any of
the materials. In this type of bubble wrap with the aluminium sides this insulation product consist of one or two layers of barrier bubble air cellular material laminated between layers aluminium foil to provide excellent thermal resistance. The air retention layer in the barrier bubble material provides increased strength and puncture resistance. Already we can say that the aluminium is shiny and would reflect the sound off, and would act like a barrier, however the bubble wrap which I will be using does not contain the aluminium therefore much of the sound particles would be able to travel through, but a large proportion would be stop by the air pockets which would retain much of the sound within the box as they would absorb the shock by the following sound waves.
In the above diagram, it is illustrated that some sound waves will hit the air pockets where they would absorb the sound and vibrate, however some sound waves will be able to travel through between the pockets and escape. Therefore I believe that bubble wrap would be moderately a good insulator of sound, which is superior to polythene however not as fine as polystyrene, as much of the sound waves will still be able to be detected by the decibel meter when using bubble wrap.
Corrugated cardboard:
I deem that a plain sheet of cardboard would not be the best insulator of sound, this is why I have chosen to use corrugated card, as this contains rigids along the plain of the cardboard, and the corrugated style in this cardboard is what is used to insulate sound. The rigids in the cardboard is what I think will insulate the sound, as the sound waves reach the corrugated card, the rigids is what cuts the sound waves and leads to the sound particles to loose energy as the rigids makes it harder for sound to travel through due to the shape and steepness of the rigids, therefore the sound particles looses energy and not all of the sound waves manage to travel through the card. This is illustrated in the below diagram:
OBSERVATIONS:
I had obtained inaccurate results from the preliminary results, this is where I had carried out the experiment, however I had used a CD player radio to produce the sound, and this is where I had inserted different insulating materials into the cardboard box layer by layer and measured the amount of sound produced through the box with the decibel meter. However looking at my preliminary results I believe that I could develop my experiment further, as the CD player radio does not produce a constant sound frequency therefore for my actual results experiment I used a sound generator and a loudspeaker.
I carried out my preliminary, as a practice test, to see whether everything had gone accordingly to plan.
- This is a table showing my preliminary results where I had inserted a CD player, into the cardboard box.
PRELIMINARY RESULTS
- This is a table of my actual developed experiment where I had used the sound generator along with the loud speaker to produce the constant sound frequency. This table shows my results from the first time I carried the experiment out:
Here are the three sets of result table; I have structured them in three simple tables showing the addition of three layers one by one for each material. Each table shows this all once, so it total from three table I have three results for each layer for each material.
ACTUAL RESULTS (FIRST SET)
SECOND SET
This is my second set of results; I had noticed that my results were similar to my first.
THIRD SET OF RESULTS
The above is a table of my final results, and they were also fairly the same as the results I had achieved before. Now that I have carried this experiment out three times fully, I can therefore conclude an average table which will average out the results from the above three tables and give overall values, this will therefore be plotted into a graph.
AVERAGE RESULTS TABLE
I consider that I had taken my measurements to the appropriate degree of accuracy, as I had rounded my number off to the nearest unit. Further I deem I had taken a large range of results, considering the time in which I had, as I obtained three results fro every layer of material which I had added on, therefore I achieved in total 36 results, before producing my average results table. Therefore I believe that I have obtained many results in order to indicate which material is the best insulator.
The above table illustrates my average results produced from the three results tables I had achieved. The average results table was used to give me more accurate results as the results extracted from the three tables are averaged out so that I achieve an average figure for each of the layers of each material.
After completing my experiment in my preliminary results I had realised that my results were not very accurate as I noticed that the frequency of the CD player radio was not constant, and this is evident through my results as they fluctuate in the case of the addition of layers of insulation, however from my scientific knowledge I am aware as the layers added are increased, the sound level measured should decrease as more sound is being insulated. I consider that a simple explanation can be derived from the preliminary results, which shows that as I had added an insulating material, once fitting this onto the cardboard box, the frequency of the CD player radio would have either increased and therefore changed, and this is when I may have measured this, and therefore my results extracted from this method are not reliable. However, I had used my preliminary results as a method to carry out before carrying out my actual experiment so if there were any problems I may incur I would not make the same mistake in the actual experiment procedure. When carrying out this experiment I had decided that an average was not needed to be taken as when I had placed the decibel meter 10cm away from the cardboard box I had realised that when using the decibel meter, the amplitude of sound detected does not tend to fluctuate by far, as the sound produced is detected after a few seconds the decibel meter produces the overall value for the sound detected. This is why in the results table there is only one reading shown for each of the layers I had added. Below is a copy of my preliminary results table showing how the results are unreliable when using the CD player radio:
Graph: From my graph I have hand drawn; we can observe that it illustrates the relationship between the amounts of layers of insulation in thickness added to the cardboard box which ranges from one to three layers, and also the amount of decibels which is detected by the decibel meter. The general interpretation of the graph is that as the amount of insulation material is increased, the amount of sound detected by the decibel meter decreases as more sound is insulated by the added insulating materials. I had drawn a line of best fit, which goes through the points, which I had obtained from my results. This is so that I could compare my readings with each material and distinguish which material is the best at insulating the sound overall. It is illustrated that on my graph I have drawn error bars to show the possible error which may be incurred, the error bars show by how inaccurate each point may be (the minimum and maximum possible value for each point). Also I had gone into more depth as I had analysed each of the lines of best fir which had represented each of the four materials, this is where I had taken the gradient of the four lines, so that I could observe the trend in the result from the gradient. I had found that as the gradient had increased the more sound which was lost. This is evident on the graph as the polythene line is extremely steep therefore is easily identified how this material is the worst insulator of sound as it firstly has the highest gradient rating of 8.5 and also detects a large value of 86 decibels on the first layer of insulation, and slowly decreases. However with Polystyrene, it is clearly evident from the graph that this is the best insulating material of sound as this firstly has the lowest gradient of 5 and secondly this is a very flat line, which is the least steepest out of the other three lines. This material is proven to be the best material as the decibel meter had only detected 76 decibel upon the first layer, 75 decibels upon the second and 74 decibels upon the third layer, which is the least amount of decibels detected. Therefore this material had retained the most sound.
From this graph, we can identify that I had achieved one anomalous result when recording the reading for the second layer of insulation for Polythene as this may been due to human error, as the sound generator produces a constant frequency, so it is not due to this factor. However, I had reduced uncertainties in this experiment by firstly carrying out this experiment three times so that I could work out an average which would be more accurate then carrying out this experiment just once. I too reduced uncertainties by making sure that I had used the same equipment and that this experiment was carried out under the same conditions so that there was no possibility that I would achieve unreliable and false results. I had made sure that all of my measurements were taken to the appropriate degree of accuracy as I had left the decibel meter for many seconds which then indicated the determined value for the sound detected. My graph indicates that the overall best insulating material is Polystyrene, which is followed by cardboard, bubble-wrap and finally polythene which I had predicted would be the worst insulating material of sound. I had used well chosen graphical plots as I had gone from 0 to 70, immediately through the symbol used, so that this had made my trend lines appear larger and had also shown more space sp that it is easy to recognise between the lines representing the different materials.
I had reduced uncertainties (errors) by making sure that the experiment was conducted in a fair test; I carried the whole experiment out three times, so that I was able to produce an average results table which gave me more accurate results then carrying this out only once. I made this a fair test by when measuring the sound level I kept the decibel meter a set distance away from the box which was 10cm. Additionally I used the same equipment so that this didn’t limit any anomalous results that I had obtained. I also carried my experiment out in the same conditions so that the temperature or any other factors didn’t affect my results from this experiment. I had used the same insulation materials and I did not alter the amount of cello tape I used to attach the insulation material to the cardboard box or onto each layer as this could have affected the layers density and reduce the sound, so I had used the same amount of cello tape to attach each of the layers together. Further I had also minimised the uncertainties by constantly checking that there was no noise in the room I had conducted this experiment in, as this would have affected my results, as the decibel meter is extremely sensitive, so to eliminate this possibly occurring I had after finishing the reading for three layers for one material, checked that the noise level was the same as before so I knew this was fair.
ANALYSIS:
From my graph it is clear that this shows the four different lines, representing the four materials I had used. As the lines generally decrease in the decibels, this is what the better sound insulator is. For example, the lines which are located towards the top of the graph are the worst insulators of sound, as the decibel; meter had detected much sound. This may simply be due to the atomic structure of the material generally allowing the sound waves to penetrate through the layers. And the worst insulator obviously would be allowing much of the sound waves to penetrate through. The results illustrate using the gradient which also helps explain the trend found within the results, as I had used the simple equation Y divided by X, and had worked out that gradient of all of the four lines on my graph. I found that as the gradient has increased resulting in a steeper gradient, this shows the more sound which escapes. Therefore using this explanation and applying it to the graph we can observe how the lines towards the bottom of the graph are more flatter and are the better insulators of sound, however the lines towards the to of the graph are extremely steep and have a larger gradient. The best insulator I had found was polystyrene as this material has the lowest gradient of 5 on the graph which I have hand drawn. The line for this material is extremely flat and not steep and this lies in the results obtained as the average results I had obtained for polystyrene for all three layers are: 76, 75 and 74 Decibels. These show the formation of the line of the graph as the readings fluctuates by one, and not by much as the sound does not seem to escape much and penetrate through this structure of polystyrene. However looking at my results, it is distinct how Polythene was the worst sound insulator and this is evident on the graph as this material had produced results of 85, 85, and 82 and this is even reflected upon the gradient which had given a result of 8.5. This had given the largest gradient therefore this also indicates how steep this line was, and looking at the graph it is clear that this is the steepest line drawn, indicating that this material had given out the most sound, as the explanation of the gradient explains how the steeper the line, the more sound which is lost. This links to the lines which are located towards the top end of the graph as, as you go up the graph you can find the instant trend, the lines become more and steeper, resulting in more sound lost. However towards the bottom of the graph, the line seems to be more flat, showing little sound loss results in the material retaining the sound. Establishing the general trend in the data is very simple as I had looked clearly at how the line of best fit was positioned, and how they were different to each other, further I had analysed the gradient and came out with the general trend which I found according to the steepest and how this links to the amount of sound which is lost. The gradient further had proved this as these positioning of the line of best fit and the gradient both can illustrate the sound loss. The relationships proposed I deem are consistent as they have evidence such as the gradient which supports my analysis of the results, and an in depth insight to the results which I had extracted for the various materials. I believe that the consistency is shown as my results follow the general trend which I had predicted, as my prediction seems to have matched correctly to the results which I have achieved. In addition in my predication I had mentioned that I thought that polystyrene would be the best insulator and polythene would be the least best insulator, according too my results this seems to be correct, as my physics knowledge had come into practice with my prediction leading me to a correct prediction. The discrepancy which I had noticed in my result lies in the material polythene where I had noticed after attaching the second layer onto the first the sound detected had remained the same at 85 Decibels; I can prove that this is an anomalous result as in my prediction I had stated that as the number of layers increase the sound waves will find it harder to penetrate through the walls of the material as they become two times more thicker if there is two layers attached. The sound molecules do not have enough energy to go through the many molecules in the material. This is even indicated on the graph where the general trend between materials as the layers is increased, the amount of sound is detected. Using the results for example looking at cardboard, the results had decreased from 80, 79 and to 77 Decibels on the third layer. I have used error bars in my graph to illustrate the possible error which may of occurred in my Decibel meter. The error bar clearly reflects my anomaly as this does not follow the pattern of decreasing as the number of layers increases. This error bar increases on the second layer, therefore the error bar indicate this anomaly clearly from this experiment. This is the only discrepancy which I had incurred throughout this experiment, I believe that I had incurred this because I deem this was down to human error when rounding off the result, I may of accidentally rounded this up, instead of rounding this down to 84 Decibels. Another reason why this is left as an anomaly is because I may of forgotten to add the extra second layer, therefore this may have jus given me the same result.
The limitations of methods, I was faced with many limitations as time was a limitation as I did not have much time to carry out my practical, as if more time was allocated I could have taken more results and also the apparatus which I had used could only be used to a certain extent, this had limited my experiment as I was not able to use more sophisticated apparatus to measure the sound produced. The cardboard box had limited my experiment as I deem if I used a larger box then I could have increased the amount of layers of insulation I had added, as I was only able to use a certain amount of layers in the box. Another limitation in this experiment was, the accuracy at which I had placed the decibel meter away from the box, as I may not have each time placed it at a set distance away, this would result in inaccurate results.
When I had carried out this experiment, I had taken extreme care over my apparatus set-up, as I had made sure that I had made this as accurate as I could possibly make it. I had ensured this because I had wanted my results to be extremely accurate as I could make them, since this is what would help me discover which material is the better insulator of sound. To achieve accurate results I had recorded my results three times, and repeated the whole process of adding the four different materials into the cardboard box and adding the layers of the insulation right up to three layers. So in total I had received 36 results for all layers and materials where the experiment was repeated three times and from this I concluded an average. I felt that this would help me to gather accurate results, which were averaged out because if I had just taken one set of results I would of experienced some errors in these results. Moreover, they would not be found and would simply give false indications of the best material for insulating sound. From my line graph which I had drawn, we can observe that as the amount of insulation material is increased, the amount of sound detected by the decibel meter decreases as more sound is insulated by the added insulating materials. The graph indicates that the overall best insulating material is Polystyrene, which is followed by cardboard, bubble-wrap and finally polythene which I had predicted would be the worst insulating material of sound. We can observe why the graph had turned out in this way leaving polystyrene to being the best insulator and polythene the worst insulator, due to the results which I had achieved as glancing at my average results table which I had calculated, it is simple to identify when adding one layer of each material and switching the loudspeaker to produce the 200 Hz signal, the sound detected for polystyrene was 76 Decibels (dB) whereas the other materials, when having one layer of insulation added achieved a higher sound rating as Polythene had achieved a result of 85 Decibels (dB) which was the highest rating for the first layer of insulation. Moving onto the results I had achieved, when the addition of the second layer it is again illustrated that Polystyrene had insulated the sound more then the other three materials therefore achieving the lowest sound reading which was 75 dB, whereas the Corrugated cardboard material had achieved the second lowest reading of 79 dB. The results indicate how well the materials can insulate the sound; however we distinguish how bubble-wrap became the third best insulator as this is illustrated on the graph which shows the results I had achieved in a graphical representation. Interpreting the graph is very simple, the curves which are drawn represent each individual material, and the curve which is nearest the lowest value for the decibel axis is what is the best insulator of sound, and as you go up the decibel axis you will find the worst insulator of sound located at the top of the graph which in this experiment is Polythene.
The simple relationship we can conclude is as the number of layers increases with any material the amount of sound detected will decrease and this is what is shown in my results table, as each of the three tables show that for any material the values decrease as the layers added increase, but to determine which is the best insulator you have to examine the lowest value detected. I have shown the relationship in the form of a diagram:
Another simple relationship I had found was in the property of the material as there are more molecules per unit then this will absorb the sound more and be a better insulator of sound. If there are fewer molecules in one material then the sound will easily be able to travel because it does not loose energy while it passes through the material as there are not many molecules to make it loose its energy. Polystyrene was the best insulator of sound due to its properties and this material has long molecules with lots of atoms joined to one another like links in a chain each molecule is composed of a string of carbon atoms joined by covalent bonds. Other atoms join on to the carbon atoms, but each carbon atom is always linked to two other carbon atoms. Covalent bonds are very strong and there is a large amount in a piece of polystyrene. This means that polystyrene is strong and durable because it takes a large amount of energy to break the covalent bonds. Polystyrene absorbed the sound waves, because of its softness and flexibility, which enabled the sound not to travel through fully. This is due to the structure of the polymer as the molecules which make up this, are very close together, therefore this means the sound waves were not able to easily travel through the material. Corrugated card had been the second best insulator of sound, which did not match my prediction as in this prediction I thought that bubble wrap would come second, however I found out it was the corrugated card simply because of the rigids along the plain of the cardboard, and the corrugated style in this cardboard is what is used to insulate sound. The rigids in the cardboard is what insulated the sound, as the sound waves reached the corrugated card, the rigids is had cut the sound waves and lead to the sound particles to loose energy as the rigids made it harder for sound to travel through due to the shape and steepness of the rigids, therefore the sound particles lost energy and not all of the sound waves managed to travel through the card. The third best insulator was the bubble wrap and I had thought that this would have been second best, however realised why the corrugated card was the better insulator as the card had the rigids which was a far better property in insulating the sound, however bubble wrap had come third best insulator due to the air bubbles which holds the air in like a cavity wall. This prevents heat from escaping and in the same way prevented the sound escaping by insulating it. However the bubble wrap I used did not consist of the silver foil in each side, as this is what would be a better sound insulator. I also learnt that bubble-wrap is more of a heat insulator then sound insulator as it is used to retain the heat in houses. Finally the worst insulating material for sound corresponded with my prediction was Polythene. This was because Polythene contains very thin walls of molecules therefore this is why the sound could easily travel through as there was not many molecules to stop the sound loosing energy therefore would lead to less escaping. However in this case the sound waves can easily pass through the thin walls of molecules, as there is not a great characteristic Polythene contains to prevent sound from travelling through. Moreover, I can conclude polythene is not a sound insulator.
The physics principle which lies in my results which I have received from this experiment, clearly matches my predication. The reason why the best insulating material which was Polystyrene had retained much of the sound was because of its structure, as this material has many molecules which are located next to each other, and they are not spread out. The molecules form a strong atomic structure and this is what prevents the sound from penetrating through. This is shown in the diagram below:
This is a typical diagram of the polystyrene structure. You can identify how the molecules seem to be positioned next to each other.
Looking at the results which I had achieved, the average results for polystyrene are 76, 75 and 74 Decibels. The results clearly show how this material sound detected had decreased each time by 1 Decibel. At the point of when the first layer was added, the result which was detected was 76 Decibels, these results immediately shows how the decibel had detected a very low sound wave, as on the graph polystyrene even when one layer is added detects the lowest sound wave. As the second layer id added, again the results show that this drops by one Decibel to 75 Decibels. The molecules in the second layer had obviously stopped and prevent further the sound waves which were trying to penetrate through. The results which I had extracted relate to the physics clearly, as in this material the results had decreased by one, as the layer increased by one. This shows that the additionally layer had provided an extra layer of molecules which the sound waves tried to go through but would not have had even energy to. The results which I had achieved for the worst insulating material which was Polythene had also related to my predication. The results which I received were: 85, 85 and 82 Decibels on the third layer. In my results it is apparent that I can distinguish that this is the worst insulating materials, this is due to the physical properties of the material as it is extremely thin, and would not contain many layers of molecules thus this had caused the sound waves to easily penetrate through. Looking and analysing my first result which I had achieved which was 85 Decibels is according to my results in the average table, the highest reading detected by the decibel meter, this instantly shows that even with one layer the sound can penetrate extremely easily, as this material does not contain many layers of molecules therefore the sound waves has enough energy to pass through the weak molecules. As this developed the results indicate once another layer was added onto the fist the reading achieved was the same of 85 Decibels; however this was an anomalous result and was due to human error. As this developed and the result of 82 Decibels was achieved this result shows that when the third layer was added the amount of sound retained had increased, however the amount of sound which was still detected was extremely large, as the molecule had easily been allowed to escape due to the high amount of energy which the sound waves contain. They can burst through the molecular structure of polythene very easily as there are not many molecules within this material. This is why the best insulating material had appeared being the best, due to the amount of Decibels which were first detected as this indicates how much sound the material can instantly retain. This all came down to the molecular structure and how the material responded to the sound waves.
EVALUATION:
I perceive that this experiment was completed under fair conditions as this was kept a fair test at all times. I consider that repeating the experiment three times, had made this fair and given the accuracy which was needed. I had ensured that I had carried this experiment out in the same day and that I had used the same apparatus. Moreover, I had carried this out in the same conditions and the same room so that I would not change the area of which the experiment is conducted in. The discrepancies I had achieved were one of my results, when taking the second layer reading of Polythene, as this result did not fluctuate from the first result at all and had remained the same. However, this is an anomaly due to the fact that as the layers are increased the result achieved should decrease, as the principles in physics supports this. So this anomaly may have been caused firstly due to a number of factors like the sensitivity of the decibel meter as this may not have deflected properly to change the reading to a different result. Further this could be due to human error, where I may not have noticed the difference in reading with minute change in the decibel meter. Further I may not have inserted the insulation properly, as this may have given the same result as I may have forgotten to cellotape it to the previous first layer. Another possibility of achieving this error may be due to the fact that I might not have sealed the box properly with cellotape therefore when recording this reading I may have been given an inaccurate result. However every precaution had been taken to ensure for the accuracy for my results, as I had made sure the same equipment was used, same conditions, apparatus and this was carried out in the same day. This anomaly is reflected in my graph as on the Polythene curve it can be identified that on the second point this remains at 85 dB, which is the same as the first reading so the line is a clear horizontal line from these two points. The uncertainty which I had achieved inherent in the data is reflected by my conclusion as I deem that this was achieved by human error, as I may have forgotten to add the second layer of insulation or may have been inaccurate when rounding off the digit to the nearest number accordingly. I believe that Polystyrene was the best sound insulator due to the large amount of molecules which it contains compared to other materials and the fact that it was reasonably thick. However I believe that the gradient had also reflected the status of the material in ranking as the steeper the gradient then the more sound it had lost, as this was illustrated on my graph and clearly shows the correlation of the materials. The first Decibel reading of each material had determined how much of a good sound insulator it had appeared to be. As in Polystyrene this had achieved a result of 76 Decibels and this appeared to be the lowest Decibel which was measured whereas Polythene had given a Decibel rating of 85 Decibels which was the highest measurement for the first layer of insulation. This was due to the fact that this material was extremely thin and contained very little molecules.
The limitations I incurred in my experimental procedure was that there was a limited availability of the materials which I had used therefore if there were more materials available this would have enabled me to expand my experiment by looking at properties of many materials. Further the apparatus were limited as they were extremely hard to get hold of there were not many available when carrying out this experiment. I deem that another limitation of the experimental procedure is that I could not have placed the decibel meter precisely 10cm away from the cardboard box every time, as the precision needed would be extremely high to do this, and as I carried this experiment out by myself this would be hard to achieve great precision this is why I carried the whole experiment out three times. From this experiment I can conclude that I had achieved minimal uncertainties as I had only achieved one uncertainty which I perceive was due to human error. I believe that my results were extremely reliable as I had carried out my experiment three times then producing an average which I had plotted on the graph, however I found that I did not plot many points, but there was a general trend which is easily noticed, as the number of layers increases, the amount of sound detected deceases. The fact that I did not have many points scattered on the graph does not make it inaccurate as I consider they should the general trend extremely obviously. The uncertainty within the data is all due to human error, and this is strongly reflected in my results table which illustrates this. The fact that I may not have inserted the second layer properly or read the decibel reader incorrectly may all be possible why I had received an anomalous result. Overall I consider that my experiment had gone according to plan with the aid of the preliminary results, as I believe this helped me carry out my experiment correctly as I encountered problems in my preliminary such as using the CD player radio which did not produce a constant frequency therefore in my actual experiment I had used a sound generator and a loud speaker. If I were to improve this experiment I would probably investigate a wider range of materials, including lead, metals and wood as I deem that this would give me a wider source of material to observe and see how well each behaves when insulating sound.
BIBLIOGRAPHY:
I had achieved information required for this coursework from the following:
- Advancing Physics AS
- Britannica Encyclopaedia
- Encarta encyclopaedia on the internet
I found that the information from these sources seemed very reliable and information I had gained, helped me understand the complex issues with the relation of physics to insulation of sound. I had obtained the various information I have included on the background information on the properties of the materials I have used from the following Internet sites:
