Cell Phone Effect on Sounds

Caleb “Raising the Bar” __________

Max “The World’s Largest 3G Network” __________

Purpose To use Fourier Analysis to compare a real-life

sound to a sound filtered through a cell phone

Our Software: Audacity

A free, open-source digital audio editor

Tests0. Nothing (control)1. Caleb note2. Piano low3. Piano medium4. Piano high5. Tuba Mouthpiece6. “background noise”7. Background conversation8. Caleb voice9. Max voice10. 440Hz11. 3520Hz12. 4000Hz

Test #1: Caleb’s Voice

Cellphone

Real-life

Test #1: Caleb’s Voice

Cellphone

Real-life

Caleb’s Voice, Zoomed In (.04 second)

Cellphone

Real-life

Analyzing the Data

Caleb’s Note, Frequencies Spectrum

CellphoneReal-life

Cell phone

Real-Life

EverythingCell phone

Real-life

Our Findings Intermediate frequencies added Frequencies dropoff at 5000 Hz

Background Conversation

Real-Life

Cell phone

440Hz note

Real-Life

Cell phone

Max’s Voice

Real-Life

Cell phone

Audacity’s Fast Fourier Transform

#1 FFT uses condensed Fourier Series

So we know this:

And also this:

So we can do this:

So we know this:

And also this:

How Cell Phones Work Cell phones are radios!

Cell phones convert analog signal to digital signal and send the digital signal to the cell tower

picture credits: wikipedia

Converting from Analog to Digital The soundwave is sampled every fraction of a

second In this process, frequencies are lost

A lower-resolution sound is producedCourtesy of howstuffworks.com

440Hz note

Real-Life

Cell phone

Why? Human hearing range is 12Hz-20000Hz Humans hear best from 1000-5000Hz

Cell phoneReal-life

Conclusion Cell phone reduces sounds above 5000Hz Cell phone adds intermediate frequencies

The End

Audacity’s Fast Fourier Transform

Sample Size Does Not Matter

Audacity’s Fast Fourier Transform

Thanks UMich!

#2 “Fourier Transformation is a Linear Operation”

“The transform of a constant times a function is that same constant times the transform of the function”

Quoted from Numerical Recipes in C, p497