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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

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, Virtual theremin. OpenStax CNX. Dec 18, 2013 Download for free at http://cnx.org/content/col11605/1.1
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