How can I know  if  the people start to speak and stop speaking?

Posted on 1998-12-06
Last Modified: 2010-04-02
My prgoram need to record people's speech via microphone.
(only in one or two minutes)

And if he haven't speak,there is only backgroup noise.
at this time I didn't want to record the sound file,
I want is When he start to say,then I start record the file.
so how can i know if he starts to speak ,
and how can i kown if he stops?

another question: how can i filter the background noise?
Question by:jackton
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
LVL 22

Expert Comment

ID: 1179390
Just analize the signal in small slices and look for an intensity that is greater than some sort of threshhold value, if it is above the value start recording (starting with that segment, not the next one).

>> another question: how can i filter the background noise?
This sort of question is the focus of many PhD thesis, scientific papers and patents.  But one basic approach is to record a short segment of the background noise and perform a fourier transform on it to get its spectral components.  Then to filter out the noise from a recording, perform a transform on the recording (short segments of it) to get the spectral components, subtract off the components of the noise.   Then perform another transform to get the "cleaned" signal.

If that is unfamilair to you, your probably should take a trip to a library and do some research on waves, aucostic signals, fourier transforms and signal processing.  
LVL 86

Expert Comment

ID: 1179391
Just an additional comment: As a (discrete) Fourier transformation consumes lots of CPU time, you should concentrate on the frequency components of interest, e.g. up to 20 kHz.
And the 'treshold' can easily be evaluated by calculating the square of the area between the signal graph and the time axis (which corresponds directly to the signal energy and is the same in both Fourier and time domain).
Another pointer: When you're already heading to the library, be sure to also look for books on Z transformation ;-)
LVL 10

Accepted Solution

Lischke earned 150 total points
ID: 1179392

as you suggested I marked this comment as answer to get the points. I'd prefer, though, that we discuss further questions in public to let other people participate.

Ciao, Mike
What does it mean to be "Always On"?

Is your cloud always on? With an Always On cloud you won't have to worry about downtime for maintenance or software application code updates, ensuring that your bottom line isn't affected.


Author Comment

ID: 1179393
Thanks all.
LVL 86

Expert Comment

ID: 1179394
What is THIS??????
Well, i think any accepted solution should be visible here, in order to not waste the points of people that reqest a PAQ!!!
LVL 10

Expert Comment

ID: 1179395
Sorry for that. See for the solution.

Ciao, Mike
LVL 86

Expert Comment

ID: 1179396
Well, IMHO, this doesn't help - see, i am not interested in this particular solution (having done enough signal processing by myself), but: If sombody is interested in a solution, requsts this PAQ, spends his/her points on it and is just redirected to a Delphi PAQ (on which points also have to be spent), he/she must consider this a hoax...
LVL 10

Expert Comment

ID: 1179397
Hey jkr,

you're right and it'll not happen again. Let's close down this fruitless discussion.

Ciao, Mike

Featured Post

On Demand Webinar: Networking for the Cloud Era

Ready to improve network connectivity? Watch this webinar to learn how SD-WANs and a one-click instant connect tool can boost provisions, deployment, and management of your cloud connection.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Errors will happen. It is a fact of life for the programmer. How and when errors are detected have a great impact on quality and cost of a product. It is better to detect errors at compile time, when possible and practical. Errors that make their wa…
Basic understanding on "OO- Object Orientation" is needed for designing a logical solution to solve a problem. Basic OOAD is a prerequisite for a coder to ensure that they follow the basic design of OO. This would help developers to understand the b…
The goal of the tutorial is to teach the user how to use functions in C++. The video will cover how to define functions, how to call functions and how to create functions prototypes. Microsoft Visual C++ 2010 Express will be used as a text editor an…
The goal of the video will be to teach the user the difference and consequence of passing data by value vs passing data by reference in C++. An example of passing data by value as well as an example of passing data by reference will be be given. Bot…

627 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question