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  • LabVIEW Digital Communications 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"

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sam_ListenForAudio.vi

Module by: Ed Doering. E-mail the authorEdited By: Brett Hern, Erik Luther, Sam Shearman

Summary: Build a LabVIEW subVI to monitor an audio input and detect when the audio level exceeds a user-defined threshold.

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_ListenForAudio.vi

  • Description: Monitor an audio input and detect when the audio level exceeds a user-defined threshold. Execution flow remains within the VI until the threshold is exceeded, at which time the subVI exits and returns the most recent block of audio.
  • Category: Speaker-air-microphone (SAM) channel ("sam" prefix)

Inputs (Controls)

  1. task ID -- U32
  2. threshold (0.1) -- DBL
  3. number of samples/ch (1024) -- I32
  4. error in (no error) -- error cluster

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

Outputs (Indicators)

  1. task ID out -- U32
  2. first block -- waveform
  3. error out -- error cluster

Required Behavior

  • Continually acquire audio samples (as in a while-loop structure) in blocks of size number of samples/ch for each of the two stereo channels. The subVI exits when the maximum value of an audio block exceeds the value of threshold.
  • The output first block contains the most recent block of audio, i.e., the block containing the audio sample that exceeds the threshold. The output is provided to subsequent subVIs that would consider this waveform to be the first block of useful (non-silent) audio.
  • The value of task ID out is identical to task ID in and facilitates clean block diagram layout for sound-related subVIs.

LabVIEW Coding Tips

View the screencast video in Create a SubVI in LabVIEW to learn the mechanics of subVIs.

Refer to the Figure 1 screencast video for LabVIEW coding tips and techniques specific to this subVI.

Figure 1: [video] LabVIEW coding tips and techniques for sam_ListenForAudio.vi
Figure 1 (subVI_sam_ListenForAudio-vi.htm)

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Definition of a lens

Lenses

A lens is a custom view of the content in the repository. You can think of it as a fancy kind of list that will let you see content through the eyes of organizations and people you trust.

What is in a lens?

Lens makers point to materials (modules and collections), creating a guide that includes their own comments and descriptive tags about the content.

Who can create a lens?

Any individual member, a community, or a respected organization.

What are tags? tag icon

Tags are descriptors added by lens makers to help label content, attaching a vocabulary that is meaningful in the context of the lens.

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