Sound Barriers
Vivienne Skriver
Grade 6
Presentation
Hypothesis
If I put metal (tin/steel) between the speaker and the decibel meter, then the sound will be blocked more than with the other materials. This is because the molecules that make up metal are very close together.
Research
Sound
Sound is energy that travels in waves that can be heard. Sound is made when an object vibrates and that vibration bumps into the molecules around it. A vibration is when molecules moves back and forth really fast. This forms a wave that eventually hits your ear and vibrates your eardrum which sends a signal to your brain.
We measure sound in units called decibels or dB.
Amplitude is the height of a soundwave from the resting point. A loud sound will have higher amplitude and a quieter sound will have lower amplitude. The resting point is when the particles aren't moving and there is no sound. The lowest part of the wave is called the trough and the highest part is called the peak. “Wavelength” is the distance between two peaks or two troughs.
Soundproofing is a material used to either absorb or reflect sound thereby reducing sound in a space. Some of the materials used for soundproofing include felt, polyester fibre, silicone and epoxy. When a sound wave hits an object like a wall, the wall will vibrate. Some sound will be reflected, some will be absorbed and some will go through. But, if soundproofing material is added to the wall, the sound will be dampened.
The Eight Materials I Tested
Wood is a hard fibrous tissue that comes from a tree. The type of wood I used is called MDF. MDF is sawdust pounded into a firm board. It is often used in furniture such as cabinets and floors. The thickness of the wood I used was 3.1mm and was firm and smooth.
Glass is an inorganic material and is hard, brittle and solid. Sand, soda ash and limestone are mixed together and intense heat melts them forming glass. In my experiment, I used the glass from a picture frame and its thickness measured 1.2mm.
Tin/Steel was one of my testing materials. Tin is a white, silvery metal. Steel is strong and made of carbon, iron and other elements. In my experiment, I used the lid of a metal container that we identified as made of tin and steel. The thickness of this material was 0.3mm.
Plastic is a man-made substance, made from oil or can be plant-based. Plastic is used for many things including packaging, dishes, furniture and machine parts. The plastic I used was a small plate that was slightly rounded and its thickness was 1.8mm.
Aluminum foil is a very thin sheet of aluminum. It is silvery white and is often used to wrap food and other items in. Aluminum foil is often referred to as “tin foil”, but is actually a different product. The aluminum foil that I used was a single sheet of Alcan Plus and is considered “heavy duty” aluminum foil. The thickness of the aluminum foil was 0.02mm.
Interfacing is a thick fabric made from 100% polyester which is a synthetic material. Interfacing is commonly used to make things like hat brims more sturdy and firm. I used interfacing because it is thicker than other types of fabric. The thickness of the interfacing measured 2.2mm.
Styrofoam is a trademark name for polystyrene. Polystyrene is a type of air-filled plastic. The styrofoam I used was from a package and its thickness measures 19mm.
Cardboard is made of paper pulp. It is often used for boxes, packages and food transport. I used a piece of single-faced corrugated cardboard. This specific piece of cardboard had a thickness of 1.3mm.
Additional Important Information About My Project
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I used a Youtube video that played one consistent sound with 300 hertz and an amplitude of 1.
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The volume of my speaker was set to “16” for the duration of the experiment.
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To ensure I was measuring the level of sound passing through my testing material, I surrounded a tube with a foam material.
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I measured the thickness of each material I tested (wood = 3.1mm, interfacing = 2.2mm, tin-steel = 0.3mm, plastic = 1.8mm, aluminum foil = 0.02mm, styrofoam = 19mm, glass = 1.2mm, and cardboard = 1.3mm).
Hearing And Hearing Protection
Hearing is one of our five senses. It is particularly important in communication. There are many challenges if we are unable to hear, so it is important to protect your hearing. Hearing begins with the outer ear first collecting the sound wave and directing it through the ear canal. The sound wave then encounters the eardrum and the eardrum vibrates the three ear bones. These bones are called the malleus, incus, and stapes ear bones.The vibration makes the fluid in the cochlea ripple. The ripple causes the different hairs to move. Different hairs wave when the sound is either high or low and little hair-like particles are bent and create little holes for the electrical current to go to the brain.
Sound is measured in decibels (dB). Normal human breathing is approximately 10 dB and fireworks are approximately 140 dB.
A sound is too loud and can damage your hearing when the decibel measurement is over 120 dB. We can lose certain ranges of hearing when we are exposed to this level of noise daily or often. There are a few ways to lose your hearing:
Aging - Your inner ear starts to change and/or changes to the nerve pathway to your brain occur.
Conductive hearing loss - occurs when there is something blocking your outer or middle ear, preventing sound waves from going into your ear.
Sensorineural hearing loss - hearing decreases when your inner ear is slowly damaged over time.
Sudden Sensorineural hearing loss - hearing is lost at one time, meaning sudden deafness.
Hearing loss that occurs when you are exposed to loud sounds - you would become deaf if you are exposed to loud sounds for a long time because the hairs get overworked and die. Loud noises could also damage the membranes in the cochlea causing you to go deaf.
We can protect our hearing by lowering the volume on certain devices such as headphones, air pods, TV, computers and phones. Going to concerts and sporting events is another source of hearing loss as many people neglect to wear earplugs or noise canceling headphones. Wearing proper ear protection around loud machinery can also help to reduce risk of hearing loss. Giving your ears a break will prevent over exposure which is a very high source of middle aged hearing loss.
Variables
Manipulated/Independent Variables:
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Wood
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Interfacing
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Tin/steel
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Plastic
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Aluminum foil
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Styrofoam
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Cardboard
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Glass
Responding/Dependent Variable: The volume of sound that passes through each material.
Controlled/Constant Variables:
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The input volume and the tone of the sound
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The box
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The sound tube
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The foam surrounding the sound tube
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The speaker
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The decibel meter
Procedure
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Gather your materials (you can add or change any of the testing materials).
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Measure the thickness of the testing materials and record it.
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Sound tube - taking two pieces of cardboard tubing, add a “gasket” onto one end of each tube. The gasket is made by cutting out two pieces of foam sheet and trace the tube, make it a little smaller so it just sits on your tube and cut out the circles so you have a square with a hole. Glue onto one of each tube ends (each tube should have one gasket).
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Cut a hole in your cardboard box and insert one tube, gasket down. Inside the box place the speaker on the ground and place the other tube, gasket up on the speaker.
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Cut out a square (make sure it's bigger than your tube) and cut a hole to stick your decimeter through so you can put your decimeter on your tube and it doesn’t fall through.
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Now insert your material so it rests on one gasket and the other is pressed on to it (make sure the tubes are lined up) cover your tubes with the sound proofing foam, place your decimeter on top of the tube that is sticking out of your box.
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Turn on the sound player and record the decibel amount that shows up on the decibel meter. Do this for each material. You will want to test each material at least 3 times so you know that one of your tests wasn’t a fluke.
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To analyze data, collect the decibel measurement for Material 1, add up the measurements and divide by 3 (or the number of trials you performed). This will be the average decibel measurement for Material 1.
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Repeat this for each material you tested.
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The material with the smallest average is the most soundproof
Observations
Qualitative Observations
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Some materials, like aluminum foil, vibrated if I didn’t push the tube down to hold the material firmly.
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I could clearly hear the tone when there was no material between the tubes.
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It was audible that different amounts of sound passed through the different materials. I could hear which materials were better at soundproofing.
Quantitative Observations
Type of Material |
Trial 1 |
Trial 2 |
Trial 3 |
Trial 4 |
Trial 5 |
open (dB) |
93.7 |
94 |
94.1 |
92.9 |
92.9 |
fabric/interfacing (dB) |
91.3 |
92.5 |
92.6 |
92.4 |
91.9 |
wood (dB) |
69.7 |
57.6 |
61.2 |
56.7 |
57.5 |
tin/steel (dB) |
88 |
77.8 |
80.5 |
83.2 |
73.8 |
plastic (dB) |
63.8 |
69.2 |
70.1 |
65.2 |
68 |
aluminum foil (dB) |
93.7 |
89.9 |
94 |
91.5 |
94 |
styrofoam (dB) |
83.4 |
86.9 |
68.6 |
58.8 |
58.9 |
glass (dB) |
84.9 |
60.8 |
52.9 |
59.5 |
57.1 |
cardboard (dB) |
91.1 |
87.6 |
90.4 |
83.1 |
82.3 |
Analysis
During my experiment, I tested the soundproofing of eight different materials with a speaker and decibel meter. My data shows that glass did the best at minimizing the amount of sound passing through. Wood was a close second. Aluminum foil and interfacing did the worst at minimizing the amount of sound, compared to the other materials. Compared to the data I got when I measured the sound without any material (93.52dB), the aluminum foil and interfacing only improved it by 1.125 dB. The data shows that my hypothesis, which stated that I thought the tin/steel would win, was wrong.
Conclusion
In conclusion, of the materials I tested, glass or wood would be your best household option to soundproof something. I made a couple of errors but I tried to control them as much as possible. In my hypothesis, I said that metal would be the most soundproof because it was dense, solid and the molecules were close together. But glass blocked the sound better because it was good at reflecting the sound.
I would like to retest this experiment focusing only on wood, glass and soundproofing foam so I can learn how glass and wood compare to materials actually designed for soundproofing.
Application
This experiment can help in the real world in many ways. For example, if you have a loud appliance like a pump or an air compressor, you can make a box using glass, put the appliance inside the box and the noise will be significantly dampened. In the real world, glass can be expensive and easily broken. The data from my experiment suggests that wood was a close second so it may be a better option for soundproofing in terms of cost and availability of materials.
Another application is if you wanted to improve soundproofing in a room. You could use some glass (or wood) on the walls, floor and/or ceiling rather than spending a lot of money for other soundproofing materials.
The reason I did this experiment was to learn which common household materials are the best for soundproofing and hopefully help people reduce sounds that are a nuisance or may damage hearing.
Sources Of Error
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One of my sources of error was that each material wasn’t the same thickness. This affected my testing because I don‘t know how much the thickness affected my results versus the type of material. An example of this is the styrofoam I used was relatively thick (19mm). If I had used thinner styrofoam, it may not have performed as well.
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Another potential source of error could be different pressure placed on the tube. My hand, placing downward pressure on the tube, is what seals it so the sound is forced to go through and not just go around the material. If I didn’t apply enough pressure, some sound could have escaped.
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The metal I tested had minor dents and the plastic material (a plate) was a bit rounded so the sound could have escaped even when we put pressure on it.
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It was challenging to put the surrounding foam into the box in the exact same way each time, potentially affecting design consistency.