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  • LV Digital Comm display tagshide tags

    This module is included inLens: Analog / Digital Communications with National Instruments LabVIEW
    By: Sam ShearmanAs a part of collections:"SubVI Specifications for "Communication Systems Projects with LabVIEW"", "Communication Systems Projects with LabVIEW"

    Comments:

    ""Communication Systems Projects with LabVIEW" features ten projects that draw upon a library of over 40 subVIs constructed as part of the project activities. Each module in this manual completely […]"

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sam_GrabAudioDynamic.vi

Module by: Ed Doering. E-mail the author

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Summary: Build a LabVIEW subVI to wait for audio level to exceed a user-defined threshold, and then record audio until the audio level drops below the threshold again.

Table 1
LabVIEWtop.png 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

Note:

Visit LabVIEW Setup to learn how to adjust your own LabVIEW environment to match the settings used by the LabVIEW screencast video(s) in this module. Click the "Fullscreen" button at the lower right corner of the video player if the video does not fit properly within your browser window.

LabVIEW SubVI: sam_GrabAudioDynamic.vi

  • Description: Wait for audio level to exceed a user-defined threshold, and then record audio until the audio level drops below the threshold again or recording duration reaches a maximum value. This subVI depends on sam_ListenForAudio.vi. In addition, sam_GrabAudio.vi should be constructed before attempting the dynamic-stop version of this module.
  • Category: Speaker-air-microphone (SAM) channel ("sam" prefix)

Inputs (Controls)

  1. frame length [s] (0.1) -- DBL
  2. max duration [s] (10) -- DBL
  3. threshold level (0.1) -- DBL
  4. fs [Hz] (22050) -- DBL
  5. error in (no error) -- error cluster

Parentheses ( ) indicate default value; square brackets [ ] designate units.

Outputs (Indicators)

  1. signal out -- waveform
  2. error out -- error cluster

Required Behavior

  • Use sam_ListenForAudio.vi to continually acquire audio samples in blocks (frames) of size frame length. Once "sam_ListenForAudio" completes execution (i.e., when the audio level exceeds threshold level), record and store audio frames until either of two possible conditions occurs: (1) maximum audio level within a frame is lower than the threshold level, or (2) total number of stored audio frames would exceed max duration.
  • The audio output of sam_ListenForAudio.vi serves as the beginning of the audio signal signal out. The last audio frame containing silence must be excluded from signal out.
  • The sound-card must be cleaned up using "Graphics and Sound | Sound | Input | Sound Input Clear" once the audio has been recorded.

Free LabVIEW Code

LabVIEW.png This subVI is rather complex to build and debug, so feel free to download the finished subVI sam_GrabAudioDynamic.vi.

You may find it helpful to test the subVI with the demo sam_GrabAudioDynamic_demo.vi.

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