Visual Sound Wave Speaker

Melde’s Experiment

A string attached to a vibration generator on one side, and a weight on the other, will create different standing wave patterns when different amounts of weight and frequency are applied.

Nodes on a String

When a string that has tension is vibrated at certain frequencies, it will produce standing waves on a string. The amount of waves, or nodes, depends on the combination of the length of the string, the type of material the string is made of, the frequency of vibration, and the tension of the string.

Waveform Function of a Song

The waveform function of an audio sample can be visualized as seen above. Where the waveform is the graph of the amplitude versus time. The goal of this project was to recreate this waveform function in the physical world.

Cost

In order to recreate Melde’s experiment, a vibration generator and a function generator are needed. However, these components are meant for scientific purposes and therefore are very expensive. We needed to come up with a solution to perform the same function as these components but at a much cheaper price range.

Current costs of these components:

Signal Generator: $840

• https://www.amazon.com/3B-Scientific-Function-Generator-Length/dp/B008N3H7J8/ref=sr_1_1?dchild=1&keywords=Power+Function+Generator+U8533600-115&qid=1601257437&sr=8-1

Vibration Generator: $228

• https://www.amazon.com/3B-Scientific-U56001-Vibration-Generator/dp/B005LY474U/ref=sr_1_3?dchild=1&keywords=vibration+generator&qid=1601257403&sr=8-3

Function

The function generator sends signals to the vibration generator to oscillate in the up and down motion several dozens to hundreds of times a second. We needed to come up with a solution which recreated this movement without the need for these expensive and bulky components.

Efficiency

While these components perform the required job, they are incredibly bulky, require a lot of power, and are not able to be programmed for the specific needs of the project.

Slider Crank

• Pros:

  • Provides desired function

  • Cheap

• Cons:

  • Not elegant.

  • Did not fit into design and vision of project.

Eccentric Cam and Follower

• Pros:

  • Provides desired function

  • Cheap

  • Fit into design and vision of project.

• Cons:

  • Hard to incorporate into base of model due to required horizontal rotary motion.

Cylindrical Cam

• Pros:

  • Provides desired function

  • Cheap

  • Fit into design and vision of project.

  • Easier to incorporate into base of model since it can be oriented different ways.

• Cons:

  • Requires precision parts

Cylindrical Cam Design #1

I created a cylindrical cam design from scratch in SolidWorks to meet the needs of our project. The cam rotates and oscillates the follower with displacement in the y-axis. The problem with this design was the narrow and shallow path in its surface as well as not being very visually appealing.

Final Cam Design

To solve the issues from the design #1, I recreated the design to feature a conical cam instead of a cylindrical cam. I also increased the depth of the path and increased the width of the path. These changes also allowed the follower to be thicker which increased its durability.

Follower

The follower is made from a single piece of material and is placed inside the path of the conical cam to create the vertical oscillation movement as the cam rotates.

Design Package

After discussing the needs of our project with team member Alberto Esses, we concluded that we needed to have speakers, a DC motor, a Raspberri Pi 4, the cam and follower design, and a power source (featured inside the base). I then created this design package including all of the components in a SolidWorks assembly for further development. The speaker, DC motor, and Raspberri Pi 4 3D models were taken from GrabCad and were not designed by me.

Design #1

After receiving a new design for the base from Alberto, I modeled it in SolidWorks and created a new assembly featuring a speaker on each of the four sides of the base, a motor, a Raspberri Pi 4 (not pictured in this assembly) and the power source (featured inside the base).

Final Design

We decided that in order to create a better auditory experience, we needed to include 8 more speakers, two on each side of the base, so that we could produce a better range of audio. We also refined the guide for the follower to be more elegant and added the conical cam design.

Creating a Physical Prototype

Using my 3D printer, I attempted to make a functional prototype. I began by preparing the model of the conical cam and follower for 3D printing using Cura. Once it had printed, I created a small structure in which a DC motor was attached to the conical cam and follower. However, this posed a new challenge as the repetitive movement of the follower on the cam started to destroy the PLA cam due to high friction forces. I am currently in the process of sourcing services to produce metal precision parts.