We chose this topic because we both love music. Sebastian has been drumming since he was 6 years old, and Erik has been playing guitar since he was 6 years old.  

We are both spectacular musicians and practice our instruments a lot. We want to preserve our hearing so that we can keep enjoying music. People who would be interested in our research are musicians who play loud instruments such as the drums and electric guitar.

Musicians suffer hearing loss from the music that they play. Some factors contributing to this include loud volumes and prolonged periods of exposure time. We would like to preserve our hearing so we are going to test different types of hearing protection. We will determine what type of hearing protection is most effective at different tones. We will be testing 3 different tones that will simulate what you hear in rock or classical music (100 hz, 500 hz, 2000 hz ).

We are designing and building an ear simulation hearing model to test different types of hearing protection at different frequencies.

We hypothesize that Bose noise cancelling headphones will be the most effective at decreasing the decibels of sound passing through our ear model because they use both physical and electronic methods.

We hypothesize that higher pitched tones will have less noise reduction than lower pitched tones at the same volume because when we have been exposed to higher tones such as a fire alarm or cymbal it causes ringing in our ears which is sign of hearing damage.

 

What is sound?

-Sound is an vibrational energy that is created by air molecules vibrating at a certain frequency and sending waves of energy at the same frequency to our ears. For sound to be produced an object needs to vibrate or be moved by a force creating a chain reaction that produces waves of energy. Sound needs molecules to move so it is impossible for sound to move in space. 

-There are also different frequencies of sound, an example of this is a dog whistle. Dogs can hear the whistle but humans can not because the sound of the whistle is a higher frequency than the human ear can hear. Humans can typically hear sound ranging from 16 Hz to 20 kHz. 

How do we measure sound?

-Sound is measured in bels, but we more commonly measure sound in decibels (1/10 of a bel). Bels are named in honor of Alexander Graham Bell (the inventor of the telephone).

How do we measure frequency?

-We measure frequency in a unit called Hertz (Hz). 1 Hz means that 1 soundwave passes any point in 1 second. Humans can usually hear frequencies from 20 to 20,000 Hz. 

How do humans hear sound?

-We hear sound by the vibrations in the air entering our outer ear causing our eardrums to vibrate. 

-Attached to the eardrum are three tiny bones that also vibrate. These bones are called the anvil, the hammer and the stirrup. The job of these bones is to amplify the incoming vibrations and project them further into the ear to the cochlea. 

-The cochlea is a snail shaped structure filled with fluid and tiny hairs called stereocilia. The sound vibrations create waves in the fluid. As the waves peak, they cause the stereocilia to bend, which converts the vibrations into electrical signals that run up to the brain.

What types of musicians get hearing loss and why?

-Musicians suffer from hearing loss because they are exposed to loud noise in performances: the average decibel level at rock concerts is 100 to 130 Decibel.

-Professional jazz and rock musicians using amplification have significant hearing loss based on the number of hours they play per week as we saw in this study. (Exposure to music and noise-induced hearing loss (NIHL) among professional pop/rock/jazz musicians, Noise Health 2015)

-This study that we found states that classical musicians are at high risk of hearing loss because most of their instruments play sounds above 85 decibels. For reference anything above 85 decibel can cause damage to your ears over time. Another reason that classical musicians are at a high risk of hearing loss is because they all sit either behind, beside or in front of one another meaning that their instruments are all very close to the other members of the group. (International Horn Society 2010 meeting, Journal of Occupational and Environmental Hygiene 2013)

What types of musicians get hearing loss and why?

The research we did showed most professional musicians get hearing loss. Some famous musicians with hearing loss include Dave Grohl, Ozzy Osbourne, Neil Young and Beethoven. 

What is pitch?

-Frequency is the number of vibrations per second when talking about a sound. 

-Pitch is the same as frequency just used in musical terms. Each note name in pitch corresponds to a specific frequency. For example middle C on a piano is 261 Hz.

-Tone is the combination of the pitch and intensity which describes the quality of a sound. 

What pitches are used in different music styles?

-Classical music has a typical range of pitches from 40 Hz (a pipe organ) to 5,000 Hz (a piccolo)

-Rock music has a range from 60 Hz (a kick drum or bass guitar) to 4,000 Hz (an electric guitar).

-A systematic review just published in February 2025 showed rock, pop, and jazz musicians had an increased risk of hearing loss >20 dB in the frequency range of 3,000–8,000 Hz versus classical musicians had higher risk of hearing loss >20 dB in the frequency range of 4,000–6,000 Hz. (A scoping review of the prevalence of musicians’ hearing loss, Front. Public Health 2025)

How do types of hearing protection work? 

1. Passive noise reduction (mechanical)

-Passive noise reduction is a method used to block out sound waves from the environment by creating a barrier between your ear and the outside sounds. 

2. Active noise reduction (electronic)

-Noise cancelling works by a built in microphone that examines sound waves coming into the microphone and generates the opposite sound wave to counter it. 

-Although noise cancelling blocks out a lot of noise, it does not block out all noise. This is actually a good thing because you can be more aware of your surroundings for safety.

3. Transparency mode

-Transparency mode works by outward facing microphones that trap ambient noise and mix it in with the music that you are hearing. 

-This allows you to hear both audio from the music that you are listening to and sounds from the outside world.

Variables: Manipulated

Different hearing protection devices

• Foam earplugs
  • Mechanical - foam
• Christmas tree silicone earplugs
  • Mechanical - silicone
• Airpod Pro (noise cancelling mode)
  • Mechanical & Electronic
• Overhead ear protection
  • Mechanical
• Bose Headphones (noise cancelling)
  • Mechanical & Electronic

Variables: Controlled

• The soundproof box used
• Volume of the pure tone played
• Frequency of tone played for each trial
• Length of each trial
• Decibel app & device used to record the decibel level
• Position of phone inside the box (distance from phone microphone to inner ear)
• Distance of the outer ear to the speaker
• Distance of the phone recording the outside sound to the speaker  
• The 3D printed ear used
• The hearing protection used for each trial (the same set of foamies used each time) 
• Soundproofing chamber and room tested in

​​​​​​​Variables: Responding 

• Number of decibels decreased by each type of hearing protection for each pure tone.

1. -scan our ears using a 3D laser scanner
2. -use a 3D printer to print the model 3D ears 
3. -create a soundproof chamber using Crazy fort, blankets and pillows. Use a carpeted quiet room. Place a foam mat inside and cover with a thick blanket or towel.
4. -trace the sides of the box onto a foam mat then cut out the pieces of the foam mats to use as an extra layer for soundproofing the box. glue the foam mat to the inside and outside of the box. drill a hole in the box the same diameter as our ear canal on the model (1 cm diameter) and mount our ear onto the box with double sided tape. Seal the ear edges with clay. 
5. -create a platform inside the box with foam blocks to mount the phone. Tape a cut bubble tea straw to the phone microphone at the bottom and cover the other 2 microphones with tape. place the phone inside the box with the microphone facing the ear canal and screen record the decibel app. Fill the box with felt and seal the lid. Cover with thick fabric.
6. -set the speaker instead cardboard box with speaker end outward. Turn on to 100% volument. Place box 3cm high on foam, 4cm from the ear canal perpendicular to the box. 
7. -place the 2nd phone on the table on foam blocks so that it is 8cm from the ground (same height as the ear canal) with the microphone end 4cm from the ear canal and 12 cm from the speaker box end. Turn on the DecibelX app on the phone.
8. -open the pure tone generator on the computer and connect the computer to a bluetooth speaker
9. -gather the different types of hearing protection
10. -turn the tone generator at 4% and keep the volume the same for all the trials
11. -play a 100 hz tone, 500 hz tone and a 2,000 hz tone - for 10 seconds each
12. -in a table record the decibel reading from outside the box for each tone and type of ear protection
13. -do a controlled trial to know how much sound the box cancelled without any hearing protection - record that data
14. -repeat the test with each ear protection type by doing the 3 tones with each ear protection in a row. 
15. -remove the phone from the box, stop the screen recording and watch the video. record the hz for each tone and hearing protection on the table
16. -Then go back and repeat the whole test again at least 2 more times so that you have done it at least 3 times. 
17. -subtract the decibel level outside the box by the decibel level inside to determine the noise reduction from each type of hearing protection. Then subtract that from the cancelling of just the box alone to determine the difference between each type of hearing protection.

-We used foam for our box because we know musicians use acoustic foam for soundproofing in their studios so we thought foam would be helpful to ensure we weren’t just measuring the difference in sound from the transmission through the box alone. Also, Erik’s mom talked to Long & MacQuade music store who suggested thick felt is another way to block sound so we added that as well.                         

-In our initial trials we didn’t have a lot of noise reduction with the different hearing protection. We did 20 sample trials in different ways trying to find the best way to get consistent results and a change in sound inside the box. Each of these below was a trial before getting to our final setup.

-We started on a table, with the box, phone and speaker all in a row. 

-We covered the outside in foam as well as inside. 

-We thought it might be because the ear was perpendicular to the speaker so we checked the decibel level inside the box with moving the ear and saw that at a 45 degree angle it was the loudest. 

-We experimented with different angles other than 45 degrees.

-We found out where the 3 microphones on the phone are so we could cover the other 2 and we used a straw to direct the sound from the ear canal to 1 speaker on the phone. 

-We experimented with different loudness of the tones.

-We put the whole setup on a foam and a thick towel to block sound transmission through the table.

-We sealed around the edge of the ear where it attaches to the box with modelling clay. 

-We put the speaker on a chair instead of the table. 

-We wrapped the whole box in a bunch of extra thick fabric and filled the box with felt so there was less airspace.

-We put the speaker in a cardboard box to direct the sound coming from the speaker into one direction.

-We built a chamber and covered it all in blankets and pillows to try to decrease background noise when we ran the experiment inside the chamber. 

-We ran these trials with the hard orange ear but we kept getting varied results so we reran 7 trials with a more flexible red ear and we got cleaner results with many of the hearing protection devices.

Subjective Results

-Airpods did not work in noise cancelling mode in our initial hard ear model because they cannot seal to the plastic like they can to the softness of the human ear. We re-did the trials with the soft red ear which let the airpods seal to the ear so we could use noise cancelling.

-Our control test was louder inside the box in comparison to outside on our 100Hz tests and our 2000Hz tests while it was quieter inside the box during the 500Hz tests.

-Based on the data we collected: 

-at low frequency (100 Hz), Bose headphones in transparency and noise cancelling were most effective. However there was not a significant difference between any types at this frequency; they were all minimally effective.

-at mid frequency (500 Hz), foam earplugs then silicone earplugs were most effective.

-at high frequency (2000 Hz), foam earplugs were significantly most effective. 

 

-Our hypothesis was incorrect because the Bose noise cancelling were not the most effective at all frequencies. At higher frequencies, the foam was most effective by a lot. We also hypothesized that the lower frequencies would be have more noise reduction than higher frequencies but we were incorrect.

 

-Our results can be explained with the following factors: 

-We think the foam were most effective because they provided the best seal in the ear canal out of all the types we tested in our model. 

-Also foam is a squishy material with air cells in it. The sound wave has to transition through the air pockets and the material which decreases the energy so that it is less powerful in energy by the time it reaches your eardrum.

-We thought the active noise cancelling should be most effective but our experiment didn’t show that. We think this because we couldn’t get the headphones to seal perfectly on the model. Our data did show the Bose were more effective in noise cancelling mode versus transparency mode because there was a reduction in decibels when we compared those two results which makes sense based on what we know about how active noise reduction works. 

-At the low and mid frequencies all the types we tested did not cancel out very much noise. 

-At higher frequencies we had very interesting results. Our passive noise reduction methods worked significantly better than any of our active noise reduction methods. Our passive noise reduction methods were also much more effective when comparing their use at higher frequencies than lower frequencies. We found that in transparency mode there was a significant increase in the decibel level at high frequency. This is important because we know that hearing loss is more common with high frequency exposures. Therefore if you use passive noise reduction devices then you are protecting your hearing more if exposed to high frequency sound.

 

-Our study is important because if musicians have hearing loss then they won’t be able to hear pitch and tone as well which can jeopardize their musical career. 

-Our study is also important because it demonstrated that the outer ear is a powerful amplifier of sound: our high frequency testing was louder in the box versus outside the box with control testing. This shows that it is very important to wear hearing protection especially when exposed to high frequency sounds. 

-Also we had incomplete sound reduction if the hearing protection did not fit properly which is important because if the person isn’t wearing or fitting their hearing protection properly then they may be damaging their hearing by amplifying the sound. 

-In transparency mode we saw that at high frequencies the decibels increased by a lot so it is dangerous to have transparency mode on while being exposed to high frequencies.

 

FUTURE IDEAS

-One future idea is to create a different type of box that is shaped like a human head. This would reduce one of our sources of error because we wouldn’t need to hold the hearing protection on the ear model and would be a more accurate representation of how hearing protection works.

-We want to test Loop earplug hearing protection as they are popular and are mechanical with a filter but they would not fit in the model ear as the plastic is too hard. 

-We would look at in-ear-monitors used by professionals but these are custom and expensive and use a different type of technology (passive noise reduction with microphones like hearing aids).

-We will add a table with the costs of the different hearing protection.

-We would like to interview an audiologist and have our hearing tested so we can better understand why there are such differences in results between the different tones.

-We would like to create our own type of hearing protection device based on the data we collected from this project.

 

 

 

-We had to try many different ways to have there be any difference between the sound outside and inside the box because our numbers were too close between them when we were first experimenting. 

-We think the biggest source of error was holding the ear protection onto the model could change the results based on how tightly it was held on and how it seals to the model.

-Some of equipment may have moved between our trials (the speaker and ear model) which could affect our data. 

-There could be variability in our readings of the decibels off the app (because we reading them with our eye). The decibel reading moved around a bit (but only by at most 0.4 decibels) during the tone being played. That is why we did more trials.

-There could be background noise which can affect our results. 

 

-The outliers in our data could be explained by any of the above variables.

 

 

https://www.mayoclinic.org/diseases-conditions/hearing-loss/symptoms-causes/syc-20373072

https://www.twinkl.ca/teaching-wiki/sound

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https://pubmed.ncbi.nlm.nih.gov/25913555/

https://sandiegohearing.com/which-musicians-are-most-at-risk-of-hearing-loss/

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https://www.masterclass.com/articles/pitch-in-music-explained

https://www.masterclass.com/articles/pitch-in-music-explained

https://www.physicsclassroom.com/class/sound/lesson-2/pitch-and-frequency

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https://ohmspeaker.com/news/different-music-different-speakers/?srsltid=AfmBOoo-t2fzetR-8Y4XRAgch-pScGVcIFgW68va911iWvWPgYXzCEcQ

https://www.hopkinsmedicine.org/health/conditions-and-diseases/hearing-loss/types-of-hearing-loss

https://www.tinnitusjournal.com/articles/response-of-human-skull-to-boneconducted-sound-in-the-audiometricultrasonic-range.pdf

 

Thank you

-Mitayo for teaching us how to use his 3D scanner so we could scan each others ears for the model.

-Our parents and brothers for helping us with materials for the project and helping us run some of the trials.  

-Mrs Saunders for signing our school up for CYSF and for paper cutting for us.