Transcript Cellphones Effect on Sounds

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
Tests
0. Nothing (control)
1.
Caleb note
2.
Piano low
3.
Piano medium
4.
Piano high
5.
Tuba Mouthpiece
6.
“background noise”
7.
Background conversation
8.
Caleb voice
9.
Max voice
10. 440Hz
11. 3520Hz
12. 4000Hz
Test #1: Caleb’s Voice
Real-life
Cellphone
Test #1: Caleb’s Voice
Real-life
Cellphone
Caleb’s Voice, Zoomed In (.04 second)
Real-life
Cellphone
Analyzing the Data
Caleb’s Note, Frequencies Spectrum
Real-life
Cellphone
Real-Life
Cell phone
Everything
Cell 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 know this:
And also this:
So we can do 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 produced

Courtesy of howstuffworks.com
440Hz note
Real-Life
Cell phone
Why?


Human hearing range is 12Hz-20000Hz
Humans hear best from 1000-5000Hz
Cell phone
Real-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