HONOURABLE MENTION

The movement of objects using sound (Acoustophoresis)

Experimentation on the movement of objects at specific frequencies of sound.
Ashanth Lingam Sahas Dissanayake
Grade 8

Hypothesis

We hypothesize that a lower frequency of sound will move an object farther from its original position than a higher frequency of sound because the research that we have acquired states that lower frequencies of sound create more vibrations than higher frequencies because they have a higher amplitude than the higher frequencies of sound. Therefore, the vibrations of the lower frequencies would hypothetically move an object farther from its original position than the vibrations of higher frequencies.

Research

  • Subwoofers require more electrical energy to create low frequencies of sound
  • Higher frequencies of sound have more energy
  • Lower frequencies of sound create vibrations because they have a greater amplitude than higher frequencies of sound
  • Infrasound is described as sound waves that are 20 hertz (lower than human audibility)
  • Acoustophoresis is the movement of objects using sound

Variables

Manipulated Variables:

  • Frequency of sound

Responding Variables:

  • Distance object travels from exposure to frequency from woofer (Type of speaker that can produce sounds from 50 to 800 Hz)

Controlled Variables:

  • Volume of frequency of sound
  • Object moved using sound
  • Weight of Object moved using sound
  • Location of experiment
  • Air pressure
  • Amount of volume and vibrations in surrounding area
  • Amount of time object is exposed to frequency transmitted from woofer

Procedure

  1. Setup experiment (Place woofer on flat surface and place object directly in front of woofer)
  2. Play 50 Hz tone for one minute on 65% volume and collect information on how far the object moved in that time period
  3. Repeat step 2 with 100 Hz, 200 Hz, 500 Hz tones and reset the location of the object being moved after every attempt

Observations

Frequency of sound in Hz 50 Hz 100 Hz 200 Hz 500 Hz
Distance object travels in CM: 2.0 CM 1.4 CM 1.1 CM 0.15 CM

 

Notes:

  • In a failed experiment, dropping an object in front of a woofer playing a low frequency of sound causes the object to fall faster than it normally would
  • The woofer used in the experiment is omni-directional

Analysis

With the observations we collected, we were able to analyze and see what happened. According to the observations Partner #1 collected, an object that was 34 grams moved 2.0 CM at 50 Hz, 1.4 CM at 100 Hz, 1.1 CM at 200 Hz and 0.15 CM at 500 Hz. With this information, we can conclude that this object moves more from exposure to lower frequencies than higher frequencies. This can also be confirmed using my sources. According to physics.stackexchange.com, "the lower the frequency the greater the amplitude of the movement... In general, all else being equal, a vibrating surface which has a fixed excursion (length of motion) will produce sound pressure levels (basically, loudness, although the perception of loudness gets complicated, and varies somewhat with frequency) which are proportional to the square of the frequency. That is, if you double the frequency you quadruple the pressure levels". This analyzed data will help us conclude this experiment.

Conclusion

During this experiment, we encountered many things that were unexpected such as the woofer not being able to move an object (this object was later replaced by a lighter object), a speaker popping loudly (causing a surprised teacher to come), and our woofer almost blowing a fuse in Partner #1's home theater setup, causing it to go into protection mode. In the end, we were able to complete our experiment and receive data that educated us and will hopefully educate other people such as the people that might read this lab. From the data that we collected during this experiment, we can conclude that our hypothesis was correct for many reasons. In our hypothesis, we had stated that, "a lower frequency of sound will move an object farther from its original position than a higher frequency of sound because the research that we have acquired states that lower frequencies of sound create more vibrations than higher frequencies because they have a higher amplitude than the higher frequencies of sound. Therefore, the vibrations of the lower frequencies would hypothetically move an object farther from its original position than the vibrations of higher frequencies". This hypothesis states all of our valid reasons and proves that our hypothesis is correct. If we were to attempt this again, we would probably use a much powerful speaker and would try more frequencies. After explaining all of our findings, we finally conclude this experiment on acoustophoresis.

Application

After collecting and processing this data, we can apply this to many things. We can inform speaker creating companies and inform them on how the enviroment and objects are affected by specific frequencies. This can help them because they can tune their speakers to play frequencies that stimulate the ears and eardrums causing speaker consumers to hear better quality and louder sound. We can also apply this to levitation machines that use acoustophoresis. This information can help reinforce the knowledge of the people who created this device and might help it become more efficient. The information might also help use these levitation machines have an actual purpose such as separating white blood cells from red blood cells. As shown, there are many purposes for this knowledge and we believe acoustophoresis can revolutionize and help the future.

Sources Of Error

Some errors that might have occured (but cannot be confirmed) include:

  • Inability to suppress all vibrations in surrounding area
  • Inability to direct all sound waves from woofer to object (woofer is omni-directional)
  • Volume of frequency tone might have not been 65% exactly during the experiment
  • The distance that the object travelled could have been incorrectly measured

Acknowledgement

We would like to acknowledge and thank our mentor Ms.Ontko for supporting us through the whole project and helping us whenever we needed it. And I would like to thank a person that I met on Discord for motivating me through this experiment.