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This module details the testing methods used to compare the three methods of encryption (frequency, phase, and echo) studied as part of the fall 2008 ELEC 301 class project.


Aural tests

As our primary objective was to make the changes inaudible, we tested all of our algorithms aurally.

We initially tested the algorithms on a 440 Hz tone to ensure that the algorithms were working as expected. (We did not test the FMAon the tone as doing so would have been silly because the tone only has a single frequency with no other frequencies to modify.)

We continued our aural testing with a suite of six songs from different genres: classical, hip-hop, oldies, pop, rock, and techno.We adjusted any thresholds and predefined constants to the point of aural imperceptibility. Working within these limits we were then able to modify theseconstants to maximize bitrate, accuracy, and noise resilience.

The following figure details the particular songs chosen and their overall frequency spectrums.

Frequency spectrums of test suite songs


Our test suite had a CD quality sampling frequency: 44100Hz, which amounts to 220500 samples for a 5 second long clip.Ideally with no noise it would be possible to use a segment length of 2 samples. This setup translates to 220500/2 = 110250 segments in 5 seconds and 110250/5 =22050bits/sec. I.e. at CD quality, we cannot get more than a 22Kbits/sec data rate.

In practice we found that Mat lab was unable to handle this amount of data. We were, however, able to successfully reach 4800segments, or 46 samples per segment. These values translate to 220500/46 = 4793 segments in 5 seconds and 958bits/sec. I.e. we reliably demonstrated a 1Kbit/secdata rate.

Power ratios

To measure how much we had changed each of the signals by encoding bits, we took a power ratio of the original signal to theoutput signal.

Formula for power ratio

Formula for Power Ratio

We found these ratios for two different input characters: ‘@’ and ‘w’. Because ‘@’ is encoded by 100 0000 in ASCII, thesepower ratios measure the minimum amount of change we make to our signals. Because ‘w’ is encoded by 111 0111 in ASCII, these power ratios measure themaximum amount of change we make to our signals.

Power Ratios
@ w @ w @ w
classical 1.0052 1.0362 1.0056 1.0352 0.9992 0.9955
hip/hop 1.0079 1.0507 1.0068 1.0413 0.997 0.9818
oldies 1.0133 1.0747 1.0069 1.0425 0.9986 0.9897
pop 1.0115 1.0776 1.0063 1.0388 0.9975 0.9842
rock 1.0131 1.0628 1.0072 1.0419 0.9975 0.9888
techno 1.0155 1.0897 1.0077 1.0463 0.9951 0.9723

Table 1. Power Ratios for each algorithm encoding one 1 per seven bits (“@”) and one 0 per seven bits (“w”)

Chart of Power Ratios

The most important feature of these results is that all of our power ratios are very close to one, indicating that we have notchanged the signal very much.

We also see some variation across the different songs because which values are changed and by how much depends on the song; forexample, with the PSA, the delay causes us to drop samples at the end of the segment, and the power in the dropped samples depends on the song.

As expected, for ‘w’, the power ratio is further from one as more one-bits are encoded. Because adding an echo can be variouslyconstructive or deconstructive, the power ratio does not reflect the number of one-bits as much as FMA and PSA. This fact also explains why the power ratiosfor the EA are generally lower than those for the FMA and PSA.

Finally for FMA and PSA the power of the marked signal was lower than the power of the original signal. For the FMA, thisdecline in power was expected because we scaled frequencies down, thus, deceasing the power in the frequency spectrum, which, as Parseval’s Theoremtells us, corresponds to decreasing the power of the signal. For the PSA, this decline in power was also expected because the PSA delays the signal in varioussegments, dropping samples in the marked signal. The EA was the only case in which the marked signal had greater power than the original signal because theechoes in this case were more constructive than destructive.

Questions & Answers

Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
characteristics of micro business
for teaching engĺish at school how nano technology help us
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
is Bucky paper clear?
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
what is biological synthesis of nanoparticles
Sanket Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Elec 301 projects fall 2008. OpenStax CNX. Jan 22, 2009 Download for free at http://cnx.org/content/col10633/1.1
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