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Overview

As the webcam theremin is purely digital, the creation of real-time audio is dependent on digital structures and processes rather than circuitry. In the implementation of the webcam theremin, we have optimized the responsivity of output and sensitivity to input of the instrument by working with effective structures and toolkits. The audio is implemented through a foundation of classes that are part of the Synthesis Toolkit package (herein referred to as STK).

Our audio input and output schematic consists of a synthesized instrument, a circular buffer, and an output stream. The instrument and its wave table can be thought of as the alphabet to be written to the buffer; the buffer then is what continuously feeds the output stream. The buffer in this case allows audio output even without a new input, so that if one holds the object controlling the theremin still, the buffer will not empty and stop the audio.

The synthesis toolkit

The Synthesis Toolkit is a digital audio development package that provides functionality to create a variety of instruments using several techniques. Classes in the STK model the clarinet, flute, mandolin, saxophone, and many other instruments. These instruments all work well with the theremin, as they have been designed by the STK to perform in real time. With the exception of the interface between the toolkit and the host's audio hardware, the entire package is platform independent and could be implemented in a variety of different settings. We decided it was important to synthesize our own sounds so we did so by a version of wavetable synthesis using a file looping class in the STK. This technique is highly flexible and could be used to re-pitch just about any sound.

Ring buffer

The ring buffer is an efficient method for storing old audio samples and queueing in new samples while maintaining continuous audio playback. A ring buffer can be thought of as an array of memory spaces where the last one points back to the first. The buffer is filled with samples by the running theremin program and after it is filled, it is constantly and quickly overwritten with new input data when it comes available. The samples are periodically written from the buffer to the host computer's audio hardware. One of the most important considerations when developing a real-time system is maintaining low latency. If the audio were to lag behind the user’s command input, the delay between input and response would be disorienting and would render the instrument unplayable. This is an area where a ring buffer excels; for a ring buffer with a fixed maximum size that will not be modified, all commands are completed in constant time. This technique of storing an array of samples is popular because these memory accesses are faster than computing new values for each sample and therefore, the ring buffer is an important part of fast audio synthesis.

Ring Buffer
Illustration of a Ring Buffer

Instrument models

The synthesis toolkit uses digital waveguide models to synthesize nearly all of its physical instruments. The underlying principles of this method are digital delay lines that represent the physical geometry of the instrument, as well as filters that model frequency-dependent losses and dispersion in the medium. Sophisticated digital waveguides may also attempt to include non-linearities specific to that instrument. A great discussion of waveguide models can be found here .

Wavetable synthesis

The audio we used most often in the theremin was not synthesized by the STK but rather in Ableton software, and read into the STK using a technique called wavetable synthesis. This approach is a very popular method of making more complex audio because it re-pitches sounds that may have complicated spectral and temporal behavior. The principle behind this technique is to vary the "speed" at which values are read from a table of samples. Strictly speaking, the signal must be periodic and the table usually contains only a single cycle of the waveform. Given the length of the table, the fundamental frequency desired, and the sampling period, one can easily compute the rate at which the data pointer must be advanced through the buffer. This is a highly flexible technique that gives our theremin a range of sound profiles.

Questions & Answers

can someone help me with some logarithmic and exponential equations.
Jeffrey Reply
sure. what is your question?
ninjadapaul
20/(×-6^2)
Salomon
okay, so you have 6 raised to the power of 2. what is that part of your answer
ninjadapaul
I don't understand what the A with approx sign and the boxed x mean
ninjadapaul
it think it's written 20/(X-6)^2 so it's 20 divided by X-6 squared
Salomon
I'm not sure why it wrote it the other way
Salomon
I got X =-6
Salomon
ok. so take the square root of both sides, now you have plus or minus the square root of 20= x-6
ninjadapaul
oops. ignore that.
ninjadapaul
so you not have an equal sign anywhere in the original equation?
ninjadapaul
Commplementary angles
Idrissa Reply
hello
Sherica
im all ears I need to learn
Sherica
right! what he said ⤴⤴⤴
Tamia
what is a good calculator for all algebra; would a Casio fx 260 work with all algebra equations? please name the cheapest, thanks.
Kevin Reply
a perfect square v²+2v+_
Dearan Reply
kkk nice
Abdirahman Reply
algebra 2 Inequalities:If equation 2 = 0 it is an open set?
Kim Reply
or infinite solutions?
Kim
The answer is neither. The function, 2 = 0 cannot exist. Hence, the function is undefined.
Al
y=10×
Embra Reply
if |A| not equal to 0 and order of A is n prove that adj (adj A = |A|
Nancy Reply
rolling four fair dice and getting an even number an all four dice
ramon Reply
Kristine 2*2*2=8
Bridget Reply
Differences Between Laspeyres and Paasche Indices
Emedobi Reply
No. 7x -4y is simplified from 4x + (3y + 3x) -7y
Mary Reply
is it 3×y ?
Joan Reply
J, combine like terms 7x-4y
Bridget Reply
im not good at math so would this help me
Rachael Reply
yes
Asali
I'm not good at math so would you help me
Samantha
what is the problem that i will help you to self with?
Asali
how do you translate this in Algebraic Expressions
linda Reply
Need to simplify the expresin. 3/7 (x+y)-1/7 (x-1)=
Crystal Reply
. After 3 months on a diet, Lisa had lost 12% of her original weight. She lost 21 pounds. What was Lisa's original weight?
Chris Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
China
Cied
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
Porter
many many of nanotubes
Porter
what is the k.e before it land
Yasmin
what is the function of carbon nanotubes?
Cesar
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
AMJAD
preparation of nanomaterial
Victor Reply
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
Himanshu Reply
good afternoon madam
AMJAD
what is system testing
AMJAD
what is the application of nanotechnology?
Stotaw
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
Azam
anybody can imagine what will be happen after 100 years from now in nano tech world
Prasenjit
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
Azam
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
Prasenjit
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
Damian
silver nanoparticles could handle the job?
Damian
not now but maybe in future only AgNP maybe any other nanomaterials
Azam
can nanotechnology change the direction of the face of the world
Prasenjit Reply
At high concentrations (>0.01 M), the relation between absorptivity coefficient and absorbance is no longer linear. This is due to the electrostatic interactions between the quantum dots in close proximity. If the concentration of the solution is high, another effect that is seen is the scattering of light from the large number of quantum dots. This assumption only works at low concentrations of the analyte. Presence of stray light.
Ali Reply
the Beer law works very well for dilute solutions but fails for very high concentrations. why?
bamidele 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 2013. OpenStax CNX. Sep 14, 2014 Download for free at http://legacy.cnx.org/content/col11709/1.1
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