Author Archives: timbrown

Group 2 Data: Lasers and Sound

For our project, we build a device to convert sound waves into patterns of laser light:


We recorded each member of the team saying a standard sentence into the device, and then took a video of the resulting pattern. We also took data regarding the volume (dB) and frequency (Hz) of each speaker.

Displayed here are three different voice recordings of one sentence, “the quick brown fox jumps over the lazy dog.” This sentence was chosen because it contains all the letters of the alphabet and would hopefully provide variation in the laser patterns produced. The patterns of one boy’s voice and two girls’ voices were measured. As seen in the video clips, deeper/lower voices/frequencies created a larger, circular laser pattern; higher pitched voices created a smaller ring-shaped pattern and also figure 8 shapes, as well.

Elizabeth’s Sentence:

Tim’s Sentence:

Becca’s Sentence:

The length of the sentence was about four seconds. The data recorded includes the video of the laser patterns, the audio recording, and the decibel recording, as well.

While further playing around with the device, we found that “P” noises (like the word “pop”) elicit a large circle, whistling into the cup and also playing music through an iPhone (classical and also bass/drum heavy) do not vibrate the balloon enough for much of a visible laser response.

Decibel levels of each speaker’s sentence:


Frequency plot of Elizabeth’s voice:



Frequency plot of Tim’s voice:



Frequency plot of Becca’s voice:



Looking at Tim’s frequency plot, there is a steep drop-off after 500Hz. This lines up with our observation that lower frequencies had more of an impact on the laser pattern, as his was much larger than the other two.

Decibel level did not have a discernible effect on the results. Much more important was the low frequencies.

We also recorded each member singing a set of three notes:

Elizabeth Singing:

Tim Singing:

Becca Singing:

Problems Encountered:

-The correct assembly of the device. For instance, less stretched balloon drum on top of the cup responded better to sounds. The application of the piece of mirror to the balloon drum was best executed using glue instead of tape, which buffered and absorbed some of the vibrations of the balloon, desensitizing the mirror and laser’s responses. The size of the mirror was also important–the heavier and larger the mirror piece, the less it would respond to vibrations. The material for the cup was also important and plastic works best (over paper). Mounting the laser onto the cup using a paperclip was best done by unfolding the clip to have two legs to tape to the cup, rather than one.

-The distance of the device and input source from the observation point, a black board. A distance of about 12.5 feet worked well for us; a longer distance increases the amount of the pattern seen.

-Playing music from a phone didn’t have enough low frequencies to move the laser a discernible amount.

Group Two Project Abstract

Our group will be constructing a device to translate sound waves into a visual representation. The device consists of a cup with a balloon stretched over one end, with a laser pointing at a mirror taped onto the outside of the balloon. As sound waves enter one end of the cup, this causes the balloon to vibrate, and reflects the light respectively.

Each person will test the device on one of three categories of sounds: differences in human voices, musical instruments, and live concerts.  We will gather the decibel level of the sound waves to see what effect this has on the size of the laser projection. We will also be filming the resulting laser projections to compare the visual data.

We plan to meet on Sundays to take data and conduct specific experiments. In addition, we will attend live concerts on campus to gather this data. We expect to find distinct patterns relating to differences in sound type and origin. We also expect that the decibel level will correspond to the size of the visuals.