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Filtering and resampling

After the song data is imported, the signal is then resampled to 8000 samples per second in order to reduce the number of columns in the spectrogram. This will speed up later computations but still leaves enough resolution in the data for accurate results.

Then the data is high-pass filtered using a 30 th order filter with a cutoff frequency around 2KHz (half the bandwidth of the resampled signal). Filtering is used because the higher frequencies in songs are more unique to each individual song. The bass, however, tends to overshadow these frequencies, thus the filter is used make fingerprint include more high frequencies points. Testing has shown that the algorithm has a much easier time distinguishing songs after they are high-pass filtering.

The spectrogram

The spectrogram of the signal is then taken in order to view the frequencies present in each time slice. The spectrogram below is from a 10 second noisy recording.

The effect of the low-pass filter is clearly visible in the spectrogram. However, local maxima in the low frequencies still exist and will still show up in the fingerprint.

Each vertical time slice in the bin is then analyzed for prominent local maxima as described in the next section.

Finding the local maxima

In the first time slice, the five greatest local maxima are stored as points in the fingerprint. Then a threshold is created by convolving these five maxima with a Gaussian curve, creating a different value for the threshold at each frequency. An example threshold is shown in the figure below. The threshold is used to spread out the data stored in the fingerprint, since peaks that are close in time and frequency are stored as one point.

The initial threshold, formed by convolving the peaks in the first time slice with a Gaussian curve.

For each of the remaining time slices, up to five local maxima above the threshold are added to fingerprint. If there are more than five maxima, then the five greatest in amplitude are chosen. The threshold is then updated by adding new Gaussian curves centered at the frequencies of the newly found peaks. Finally the threshold is scaled down so that it decays exponentially over time. The following figure shows how the threshold changes over time.

The threshold increases whenever a new peak is formed around that peak’s frequency and decays exponentially over time.

The final list of the time and frequencies of the local maxima above the threshold are returned as the song’s fingerprint.

Questions & Answers

what is Nano technology ?
Bob Reply
write examples of Nano molecule?
The nanotechnology is as new science, to scale nanometric
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
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.
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Digital song analysis using frequency analysis. OpenStax CNX. Dec 19, 2009 Download for free at http://cnx.org/content/col11148/1.1
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