Noise Cancellation Reduction Introduction Biology Essay

Ever wondered what sound is and how its created? Why hearing loss occurs? Or how noise cancellation earphones work? Even the ground for the concern you get from piercing noises? Every twenty-four hours we depend on our hearing to acquire us through day-to-day activities, leisure, communicating, work, and life itself. Although we are surrounded with sound and noise each twenty-four hours, most of us bury the unbelievable creative activity of these simple accesities. Sound is made up of quivers that travel in a longitudinal moving ridge where the atoms move in the way of the moving ridge in a parallel form. These atoms bump into each other as they transfer kinetic energy whilst the moving ridge makes its manner towards our ears. The sound moving ridge is collected by the outer ear, moves into the ear canal and bumps against the tympanum. This vibrates the tympanum that affects the bantam castanetss in our in-between ear. Vibrations of these castanetss hit a tubing called the cochlea ; these quivers are so changed to electrical urges which are called cilia that are attached to our audile nervousnesss. The cilia moves which in bend make the nervus cells react, directing signals to our encephalon through the auditory nervus. Our encephalon so interprets the sound as sounds or words we have heard before, but does non state you the significance of it ; this is what hearing is for.

Figure 1: How our ears interpret sound ( Ref: hypertext transfer protocol: //www.learningthroughlisteningHYPERLINK “ hypertext transfer protocol: // ” .org/Listening-A-Powerful-Skill/Listening-and-Learning/Benefits-of-Teaching-Listening/93/ )

Sound moving ridges can go through through solids, liquid, and gas. Sound transmits through solids the fastest as the atoms can knock into each other easy and faster because of its solid signifier, compared to a gas where atoms take longer to knock into another atom. This supports the fact that sounds moving ridges are sound energy a signifier of kinetic energy where with energy the atoms move faster reassigning that energy, so the sound will be transmitted quicker.

Examples of kinetic energy are things that move, such as a rollercoaster ‘s, a resiling ball, or a slug fired. If an object has kinetic energy, there are things within that object such as moving ridges, atoms, negatrons, and molecules that cause it to travel. There are 3 types of kinetic energy ; vibrational ( energy as a consequence of vibrational gesture ) , rotational ( energy because of rotational gesture ) , and in conclusion translational ( energy due to the motion from one topographic point to another ) . The sum of kinetic energy going faster depends on the weight and velocity of an object. The faster and heavier an object is, it has more kinetic energy, compared to another object that may be lighter and slower.

Figure 2: Kinetic energy illustration ( Ref: hypertext transfer protocol: // )

This is the equation used to mensurate kinetic energy KE = A? * m * v2. Here, thousand represents the mass of the object, and V represents the velocity of the object. The faster the velocity of the object goes, the more kinetic energy it will possess. This is the same for the denseness of an object. The denser an object is, the closer the atoms are formed together. When the energy passes through it is easier and faster through solids because the atoms are closely packed together in a manner that transfers this energy from one atom to another.

Figure 3: Mass ( denseness ) and velocity ( speed ) of the equation for kinetic energy ( Ref: hypertext transfer protocol: // )

Kinetic Energy Info ( Ref: hypertext transfer protocol: // )

Within a sound moving ridge you will be able to place a wavelength, frequence, and amplitude. The wavelength is used to mensurate how long a moving ridge is till its following indistinguishable moving ridge. The frequence tells us how many moving ridges there are per second, this is measured in Hz. Last the amplitude of a moving ridge will demo us the air force per unit area, the scope will get down on the line where the moving ridge comes up and halt on the highest graduated table mensurating up or down. The amplitude is related to the volume of the sound you are listening to, as the amplitude is measured in the likes of its force per unit area. The higher the force per unit area, the louder the sound will be. Amplitude is measured in micropascals, but existent sound is measured in dBs. Hearing AIDSs are made to magnify the noise of the milieus you face each twenty-four hours, so people with the disablement of hearing will be able to hear noises like other people usually with their hearing AIDSs on as the volume will be increased in the mechanical device. An illustration of this will be the usage of spectacless ; the lenses are particularly made to prescriptions that meet the normal measurings of sight.

Figure 3: Features of a sound moving ridge ( Ref: hypertext transfer protocol: // )

The opposite creative activity of hearing AIDSs would be noise cancellation devices such as earmuffs, ear buds, canal caps, earphones, etc. Nowadays we see the modern universe full of life, busy, exciting and noisy. So it was n’t a surprise when innovator Lawrence J. Fogel foremost came up with the construct of noise cancellation earphones to barricade out unwanted sound from the background and Dr. Amar Bose made the first set of earphones that advanced the engineering. ( Ref: hypertext transfer protocol: //en.wikipHYPERLINK “ hypertext transfer protocol: // ” & A ; hypertext transfer protocol: // )

There are 2 types of noise cancellation, active and inactive. Active noise cancellation is when you hear a sound and the device actively produces the same sound frequence 180A° at the same clip that is called anti-noise. When these 2 semen together the anti-noise naturals out the existent noise which will ensue in silence in the existent universe

Figure 4: Sum of moving ridge ‘s equal silence ( Ref: hypertext transfer protocol: // )

Some active noise cancellation earphones can non ever produce the anti-noise that precisely the same clip and frequence. If this happens the amount of the moving ridges will look slightly like this ;

Figure 5: Sound wave fraction of a 2nd excessively late ( Ref: hypertext transfer protocol: // )

Passive noise cancellation is when the device is created with stuff that creates a kind of defense mechanism against sound by either absorbing or reflecting it. High denseness stuffs are layered over each other to supply the best signifier of inactive noise call offing this is a fillip for music earphones. Passive noise cancelling is less preferable because the stuffs are normally rather heavy and if there is excessively much it is uncomfortable to utilize.

Figure 6 & A ; 7: Noise cancellation caput phones and how they work ( Ref: hypertext transfer protocol: // )

Apart from devices made for leisure, on the market there are now points being made and sold to forestall people from damaging their hearing particularly in working environments. These include ear muffs, ear buds and canal caps. The section of labor has late made new demands and reassessed their systems for work topographic points with noisy environments such as mills, machineries, building and edifice. A transcript of these alterations in appendix1 ( Ref: hypertext transfer protocol: // )

Most points suggested by the Department of Labour are 1s that passively cancel out noise, but which devices cancel out noise the most? Why do some stuffs merely barricade out some noises? How do the stuffs absorb or transmit sound? There are many anticipations and theories made to propose what stuffs block sound the most, to possibly support or formalize the theories of others and ourselves we will be replying these inquiry in an independent experiment that aims to happen out which stuffs cancels/reduces noise the most. We will make this by utilizing 10 stuffs ; wood, stone, sponge, metal, cotton wool, composition board, polystyrene, plastic, and insularity. These stuffs were chosen for the different signifiers of denseness and mass ; we set out to happen out if these stuffs provide the best defense mechanism against sound or increase the noises we hear.

I predict that out of the 10 stuffs brought in to utilize for our experiment, stuffs like the insularity, cotton wool, sponge and polystyrene will be rather effectual and successful in cut downing the unwanted noise we will be bring forthing. This is because these stuffs are of low denseness and the quivers will be absorbed passively instead than reflected or transmitted. Having a lower denseness in a stuff will decelerate down the kinetic energy going through the stuff. In this instance it will be the sound waves, the greater the mass of an object the faster or greater kinetic energy is being possessed or going. By absorbing the quivers, points like these are known for its comfort and sound-proofing. An illustration of this is the insularity put indoors walls whilst edifice or retracing a house, holding insularity inside walls will assist barricade sound moving ridges yet keep the place warm sufficiency with the energy absorbed by the sound waves.

Figure 8: Sound soaking up ( Ref: hypertext transfer protocol: // )

Figure 9: Home insularity block out sound moving ridges ( Ref: hypertext transfer protocol: // )

In this probe we got into groups and did one large experiment together due to the deficiency of equipment and clip. Our independent variable is the 10 different stuffs we are utilizing ; wood, stone, sponge, metal, cotton wool, composition board, polystyrene, plastic, and insularity. Our dependent variable is the different graphs of the sound moving ridges captured by the mike. The control variables that we kept the same in this experiment is the ice-cream container that holds the stuffs, the mike, the talker, the frequence, clip, amplitude, and wavelength of the sound produced, every bit good as the room we were proving in. By holding these factors the same we are able to vouch a just trial, and valid consequences. Like any other probe, we have tested each stuff 3 times ; to mensurate the moving ridges, calculate an norm, obtain accurate consequences, and do certain decisions.


We found a room that would be soundless and vacant for a long period of clip, so we set up the talker system on one terminal of a tabular array.

On the other half of the tabular array we put in our 1st stuff into the ice-cream container.

Then placed the container precisely 15cm off from the talker, and had it standing like this ;

Figure 10: Ice-cream container construction

– We marked a line so we did non hold to mensurate each clip we moved the container to set in a new stuff.

Behind the container, we measured 3cm and used a clinch to keep the mike in topographic point. We had the detector confronting the container ‘s dorsum.

Then put the talker to… Throughout the experiment we kept this sound the same, to do it a just trial as one of our control variables.

We connected the mike to a laptop that has package called Logger Pro Version 3 downloaded and installed, so opened it up.

We were certain to hold a new graph ready. By snaping into scenes, ticked the box for repetition and preset the clip to 0.05 seconds.

When everything was set, we put the talker on, and so clicked the cod button on the screen of the laptop.

Patiently we waited about 3-5 seconds so clicked stop, we got a graph.

To do the graph larger, we clicked on a button called Auto graduated table, to enlarge the graph.

We saved it into a booklet, named it the object we were proving so we did non blend it with any other graphs from this experiment.

This was done 3 times for the same stuff.

After the 3rd clip, we took the ice-cream container and emptied the contents. Then inserted another stuff to prove, and placed the ice-cream container at the same grade we made for 15cm.

We did this for all 10 stuffs so in entire we collected 30 graph informations ‘s raw.

We understood that it was really of import that the room was rather at all times in this experiment as any other sound moving ridges could hold been collected by the mike.

When all informations had been collected, we packed up everything.

Subsequently on we printed out all the graphs to label and run off for the remainder of our squad members.

We were careful to maintain them separated from each other, if some graphs got assorted up with another stuff graph we would acquire consequences that would non be accurate, and the experiment will necessitate to be repeated. For illustration, if a metal graph got assorted with a plastic graph the norms we get form mensurating the moving ridges would non be valid so these can non be used for our consequences, experiment, or decision.

Last we measured the moving ridges on our graphs by pulling a line and calculating out the most lines in the highest amplitude and the lowest, subtracted them and got our reply. This was done with 3 graphs for each stuff, to happen our norm we added the values from all 3 graphs, and divided it by 3. This is done to convey in our consequences and conclude this experiment.

Figure 11: Experiment layout

Consequences: Graphs seen in Appendix 2

Out of the 10 stuffs we have chosen to experiment with to happen out which 1s can reduce/cancel resound the best, we have chosen 5 chief graph consequences to concentrate on ; plastic, polystyrene, metal, insularity, and sponge. All these stuffs have similar every bit good as different constructions, substances, denseness, mass and weight. This is ideal for our chief purpose to happen out what material naturals or reduces noise the best, and will either support or convey in new anticipations towards our hypothesis and the theories of other beginnings.

After carefully mensurating the different graphs, rounding them up to the nearest point, and happening out their norms. We have come to recognize that within the 5 stuffs we have chosen, plastic is the worst at cut downing sound with amplitude of 0.013, so comes metal with 0.011, after metal we see polystyrene and insularity non excessively far off both measured with amplitude of 0.010. Last our most successful stuff was sponge, merely somewhat exceeding both polystyrene and insularity with mean amplitude of 0.009.

In our consequences we see that all the amplitude norms were non excessively far out of range from each other, they are all seen one or two points off from one another ‘s material amplitude. This tells us that this is a valid experiment that was done in just conditions and came up with dependable consequences. If we were to hold consequences that are highly different to what we have now, such as 10 point difference these would non be consequences that can be relied on to derive an accurate decision as they do non fit any other norms and show no tendency. Our lone option would be to remake our experiment, and have recount where we might hold gone incorrect.

There were merely 2 stuffs that were in the exact same scope as one another ; the insularity and polystyrene. This did non come as a surprise to me as I suspected that they would fall in the same graduated table because of the similarities in the facets of their stuffs. Both these stuffs have been known for their usage in energy preservation and thermic opposition. They are formed in a manner that protects something or person, blocks sound moving ridges to supply noise control, and warm its milieus. This is why nowadays we can see them combined together to bring forth the best sort of protection. Appendix 3

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Differences between Each Trial of All Materials Measured In Percentages Compared To Plastic ( Our Highest Value in Our Consequences )


1st Trial

2nd Trial

3rd Trial

Entire Graph Average

Entire Percentage Average


0.013-0.008×100= 50 %

0.013-0.011×100=20 %

0.013-0.012×100=10 %

30 %

26.6 %

Metallic element

0.013-0.012×100=10 %

0.013-0.010×100=30 %

0.013-0.012×100=10 %

20 %

16.6 %


0.013-0.006×100=70 %

0.013-0.011×100=20 %

0.013-0.013×100=0 %

30 %

30 %


0.013-0.008×100=50 %

0.013-0.008×100=50 %

0.013-0.013×100=0 %

40 %

33.3 %


0.013-0.010×100=30 %

0.013-0.010×100=30 %

0.013-0.009×100=40 %

40 %

33.3 %

In the tabular array above we can see that the differences of decrease between sponge and an empty container compared to the consequence of plastic have a great per centum of differences. Compared to plastic, sponges and a vacant ice-cream container cut down 36.65 % more noise than plastic can. This makes them about 1/3 more dependable so plastic in barricading out sound moving ridges. Next we have both polystyrene and insularity coming to a sum of 29.15 % in wining to cut down sound compared to plastic ( 26.6+30=56.6 /2=28.3 +30=58.2 /2=29.15 ) . This is about higher than 1/4 of plastic ‘s consequence on the sound waves collected. Last the stuff that does non hold a important alteration to the impact plastic made is metal, with merely an 18.3 % difference between plastic and metals decrease of sound ( metal about 1/6 better at cut downing sound so plastic ) these 2 stuffs are our worst at diminishing the noise we hear.

Between our best and worst sound cut downing stuffs, plastic and sponge has merely a.004 point difference but on the graduated table of strength there is a 30 % difference on the decrease of sound. This tells us that even though these two points have different visual aspects, textures, volume and mass. They have some indistinguishable qualities in the stuff that block sound moving ridges in a similar form.

In decision, I think that our worst sound cut downing stuffs like plastic and metal resulted last in our consequences because it relates back to the equation of kinetic energy. The denser our stuff the faster sound energy travels. Plastic and metal is our most heavy stuffs compared to insularity, sponge, and polystyrene ( polystyrene did non make full up the whole ice-cream container, my anticipation is that in entire plastic would hold been denser compared to the polystyrene ) . Therefore the sound waves base on ballss through these stuffs slower with barriers in the manner. With the metal and plastic it speeds up this procedure because of the atoms in these stuffs closely formed together.

Although metal is denser than plastic, plastic did a worst occupation at cut downing sound. This is because the metal we used in this independent experiment was from parts of a auto, bolts and nuts that were remarkable and little piled up together. A immense factor that influenced the consequences we collected was the fact that the single metals were sealed tightly in a glad wrap when put into the container. The overall sum of metal merely reached an approximative halfway grade in the ice-cream container and would hold weighed down when the container was prompted upwards as seen in figure 8: ice-cream container construction. The sound moving ridges had a batch of air infinite to go through through in between the different spots of metal, and kinetic energy travels slower in air so in solids, this is why I believe that metal came 2nd in our worst stuffs list. If a big ball of metal with no holes, or losing parts was used I strongly believe that metal would be our worst stuff to cut down sound as the sound wave have no barriers to decelerate it down or be absorbed, the atoms would be tightly held together and rub off energy from each other easy with velocity, and the denseness of the metal supports the velocity of sound with kinetic energy.

Associating back to our tabular array above, within our tests, our major differences are insularity and plastic ( 0.013-0.006 ) and insulation/sponge compared to plastic ( 0.013-0.013 ) . Our first test of insularity told us that compared to fictile insularity has a 70 % difference in the decrease of sound, this is a astonishing fraction of 5/7 better dependability. Another noteworthy alteration was insularity and sponge ‘s 3rd tests both measured 0.013 in exact with the value we are comparing it to which is the plastic. This means for these 2 tests they gain no differences in the public presentation of cut downing sound compared to plastic. I think these graph information ‘s collected was non accurate, because of the other tests ‘ consequences we can see that they vary in difference. For illustration ; insularity ‘s 1st test resulted in 0.006, 2nd test 0.011, and last test 0.013. Within these consequences the differences between each one collected range every bit high as 5. I believe that this is a mark of something we may hold done incorrect or different with each test. Such as mundane background noises could hold been collected by the mike analysed in the consequences. During the experiment, we had rather a few people in the room so other background sounds like person feeding, a door shutting or the sound of typing on a computing machine could hold easy been collected by the mike if the sound was in close scope.

Furthermore our mean sound force per unit area for an empty ice-cream container is 0.009 ; all our other consequences we have collected show us that these stuffs really increased the amplitude of the sound we produced. There are no stuffs that reduced the sound, alternatively we see that sponge has the same sound force per unit area as our empty container, as for the remainder they steadily increased the volume of our sound doing it louder than earlier after traveling through the stuffs in the container. Our best stake on a noise decrease stuff ( within the scope of the stuffs we tested ) will be the sponge. Even though our norm from all 3 tests shows us that sponge did non increase or diminish our amplitude of sound, it has the lowest sound force per unit area with a difference of.001 out of the 5 stuffs we tested. Sponge ‘s minimal mass/volume could be the ground for this ; we had about 5 sponges in the ice-cream container this left infinite for air between each sponge, so even if the sponge absorbs some of the sound moving ridges and converts them to heat energy there are air infinites in the container that transmits the sound through the container and into the mike. Refraction of sound moving ridges could besides be another ground.

Refraction of sound moving ridges is the alteration of way these sound waves travel at when go throughing through one medium to another, this changes the speed/velocity of the sound waves. In our experiment when the sound waves reach the container, they pass through but at a different velocity I predict it will be faster. With this new velocity the way bit by bit changes excessively, the new velocity of sound moving ridges in air is determined by the temperature on the surface, with this equation ( c=331 + 0.6 T ) where T is the temperature in grades. For illustration if the air is cooler down on the land sound moving ridges travel slower here compared to a temperature incorporating heat above the land providing velocity to the sound waves produced. This is called a temperature inversion, and supports our beginnings for kinetic energy. In our instance, when the sound was being collected by the mike the sound moving ridges could hold turned a new way and gained a new velocity due to the temperature of the room and the transition of captive sound moving ridges to heat energy.

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Apart from refraction and air infinites, other facets of our probe could hold influenced the consequences we attained and the overall decision towards this experiment. We can non be certain about the truth of this experiment ; even if we have tried to add a fraction of dependability towards this experiment by holding collected 3 different graph informations ‘s for each stuff. The manner we measured our graphs, calculated our norms and noted our alterations are all done independently, so our consequences may change from the same experiment. Possible ways to better our overall probe would be to roll up more readings of our graph informations ‘s for each stuff so we can be certain that our consequences can be relied on. Repeat our experiment a twosome of times, to derive a higher degree of truth and to meet any mistakes or new sets of informations different to the 1s we have collected now. By reiterating our experiment we can besides back up, back-up or alter our current information to suitable address our consequences. Equally good as compare the new graphs to the 1s we current have now, to place any new leads or unobtrusive breaks in our first experiment. We could besides do certain the quality and measure of our stuffs are within just variables, all the same sum ( make full up the whole ice-cream container ) , no air infinites, etc. By making this we might really derive consequences that cut down, absorb and reflect sound.

Weak countries of our experiment include our set up, the measurings of the mike, and the arrangement of the ice-cream container off from the talkers. We merely allowed a 3cm spread between the dorsum of the ice-cream container and the detector of the mike. This is non ideal if possibilities of refraction occur as the mike would non be able to travel in waies the sound moving ridges are going in. We could put the mike farther off from the container around 10-15cm to extinguish opportunities of refraction. The ice-cream container we used was besides a confining factor to this experiment, alternatively of utilizing an ice-cream container to keep the stuffs we are proving we could hold measured the sound waves straight on or a few inches off from the stuff itself to better our truth when mensurating our amplitudes, norms, alterations, and composing up our decisions. Having the ice-cream container placed in the place and distance it was in this experiment, gives us less accountable consequences and arises inquiry as to why a peculiar stuff does better/worst than expected. In overall rating, the method we used in this experiment has seen success in conveying the consequences we were anticipating every bit good as those we did non. With the limited clip, resources and planning we had I can confidently state that this probe have been completed to the best of our abilities.

-Alice Ao