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Linear prediction coding (LPC) models a speech signal as a time-varying filter driven by an excitation signal. The time-varying filter coefficients model the vocal tract spectral envelope. “Cross synthesis” is an interesting special effect in which a musical instrument signal drives the digital filter (or vocal tract model), producing the sound of a “singing instrument.” The theory and implementation of linear prediction are presented in this module.
This module refers to LabVIEW, a software development environment that features a graphical programming language. Please see the LabVIEW QuickStart Guide module for tutorials and documentation that will help you:
•Apply LabVIEW to Audio Signal Processing
•Get started with LabVIEW
•Obtain a fully-functional evaluation edition of LabVIEW


Subtractive synthesis methods are characterized by a wideband excitation source followed by a time-varying filter. Linear prediction provides an effective way to estimate the time-varying filter coefficients by analyzing an existing music or speech signal. Linear predictive coding ( LPC ) is one of the first applications of linear prediction to the problem of speech compression. In this application, a speech signal is modelled asa time-varying digital filter driven by an innovations sequence . The LPC method identifies the filter coefficients by minimizing the prediction error between the filter output and the originalsignal. Significant compression is possible because the innovations sequence and filter coefficients require less space than the original signal.

Cross synthesis is a musical adaptation of the speech compression technique. A musical instrument or speech signal serves as the original signal to be analyzed. Once the filter coefficientshave been estimated, the innovations sequence is discarded and another signal is used as the filter excitation. For example, a "singing guitar" effect is created by deriving the filter coefficients froma speech signal and driving the filter with the sound of an electric guitar; listen to the audio clips below:

  • speech.wav -- Speech signal for digital filter coefficients (audio courtesy of the Open Speech Repository, www.voiptroubleshooter.com/open_speech ; the sentences are two of the many phonetically balanced Harvard Sentences , an important standard for the speech processing community)
  • eguitar.wav -- Electric guitar signal for filter input
  • speech_eguitar.wav -- Cross-synthesized result (filter output)

Linear prediction theory

The screencast video develops the theory behind linear prediction and describes how the technique is applied to musical signals. Practical issues such as choosing the filter block size and filter orderare also discussed.

[video] Theory of linear prediction and cross synthesis

Linear prediction implementation

The previous section explains how you can use the all-pole filter model to implement cross synthesis. But how are the all-pole filter coefficients actually created?

The LabVIEW MathScript feature includes the function lpc , which accepts a signal (1-D vector or array) and the desired filter order and returns an array of filter coefficients.For details, select "Tools | MathScript Window" and type help lpc .

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, Musical signal processing with labview -- subtractive synthesis. OpenStax CNX. Nov 07, 2007 Download for free at http://cnx.org/content/col10484/1.2
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