# 0.4 Implementation

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## High level design

The high level design of our project is as follows. We have a Behringer UCA222 that serves as the interface between the pickup in the guitar and the computer. The final output is played on the speaker that is connected to the UCA via a 3.5mm audio jack. The UCA222 takes the guitar input through dual channel RCA ports and forwards the signal to the computer through USB. We then do computation and analysis, in Python, on the sample signal to determine the frequency and the identity of the note being played, and depending on the note synthesis the correct harmony. The synthesized signal is fed back into the UCA222 and outputted on the speaker.

Figure 1: Block Diagram of our System

Figure 2: Picture of our Setup

## Sampling and frequency analysis

We sampled the analog signal of the pickup through the UCA222. The UCA222 is programmed to anti-alias and sample and forward the data into system audio. We can then access system audio via a Python library called PyAudio. PyAudio is able to give us vectors of the samples of a desired length. Compared the difference in latency to our system between different vector length and decide that 1024 was a good middle ground. We decided to further lowpass filter the sampled chunks to reduce high frequency noise introduced by the ‘fret-buzz’ and the initial attack of the guitar string.

```import numpy import pyaudioimport scipy import math# constants fs = 44100.0CHUNK = 1024 cutoff_hz = 8000.0nyq_rate = fs / 2. # for normalizing width = 1000.0/nyq_rateripple_db = 30.0 # open pyaudio streamp = pyaudio.PyAudio() stream = p.open(format=pyaudio.paFloat32,channels=1, rate=44100, input=True,output=True, frames_per_buffer=CHUNK)# build filter N, beta = scipy.signal.kaiserord(ripple_db, width)taps = scipy.signal.firwin(N, cutoff_hz/nyq_rate, window=('kaiser', beta)) delay = 0.5 * (N-1) / fswhile(True): data = stream.read(CHUNK)x = numpy.fromstring(data, dtype=numpy.float32) x_filtered = scipy.signal.lfilter(taps, 1.0, x)X = numpy.fft.fft(x_filtered) stream.close()p.terminate()```

From this, we are able to analysis each frame of 1024 samples and compute the frequency content of the frames. We played a few different notes and plotted the frequency content of notes in hopes of figuring out a good way to differentiate between notes. Below are plots of a note being struck in the time domain, and frequency spectrum plots of a high and low C note.

Figure 3: Time Domain Plot of a note being played

Figure 4: Frequency Spectrum of a High and Low C

## Note identification

After looking at the frequency domain, it is obvious that each note has one distinct peak at a particular frequency. So we decided to do note detection by finding the frequency with the largest magnitude. In other words, we are doing max-peak detection. In doing this, we took the absolute value of the frequency bins in the positive half of the spectrum and use the argmax function from the NumPy library obtain the frequency bin with the highest peak. However, in using this method we very quickly encountered a problem. When a certain note is played on the guitar, though the profile of the note in the frequency domain will not change very much, the maximum peak in fact moves around a little. Because other approach only looks at the highest peak, sometimes we will get errors when the neighboring peaks overtake the correct main peak in magnitude. When this happens our program will think the note is quickly changing, but actually it is just the same note reverberating through the guitar.

are nano particles real
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Joseph
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Lohitha
where we get a research paper on Nano chemistry....?
nanopartical of organic/inorganic / physical chemistry , pdf / thesis / review
Ali
what are the products of Nano chemistry?
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
learn
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
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da
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Bhagvanji
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Giriraj
Preparation and Applications of Nanomaterial for Drug Delivery
revolt
da
Application of nanotechnology in medicine
has a lot of application modern world
Kamaluddeen
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narayan
what is variations in raman spectra for nanomaterials
ya I also want to know the raman spectra
Bhagvanji
I only see partial conversation and what's the question here!
what about nanotechnology for water purification
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
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Professor
I think
Professor
Nasa has use it in the 60's, copper as water purification in the moon travel.
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Rafiq
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Damian
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What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
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Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
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Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
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Anam
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
Hafiz
what is Nano technology ?
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
what king of growth are you checking .?
Renato
how did you get the value of 2000N.What calculations are needed to arrive at it
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