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Document Type: Example Program
NI Supported: Yes
Publish Date: Sep 6, 2006

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Echo Detection Using Hilbert Transform

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Filename: echo_detector.llb
Requirements: View

This program shows a simulated acoustical response in a room with an echo. The echo signal arrives at a time that overlaps with the excitation signal, so that it is very difficult to see in the traditional "oscilloscope" type display. The Hilbert transform is used to computed the analytic signal (i.e. a signal with the same frequency content, but with all frequencies shifted 90 degrees). By squaring the original "real" signal as well as the "analytic" signal, it is possible to compute the vector length (envelope) as the square root of the sum of these two signals.

Notice the very clear bump on the Echogram and notice how it coincides with a zero crossing of the original signal, where the echo signal is "overshadowed" by the very rapid change of the signal as it passes through zero.

Requirements


Filename: echo_detector.llb

Software Requirements


Application Software: LabVIEW Full Development System 6.0
Language(s): LabVIEW

 
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This example program (this "program") was developed by a National Instruments ("NI") Applications Engineer. Although technical support of this program may be made available by National Instruments, this program may not be completely tested and verified, and NI does not guarantee its quality in any way or that NI will continue to support this program with each new revision of related products and drivers. THIS EXAMPLE PROGRAM IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND AND SUBJECT TO CERTAIN RESTRICTIONS AS MORE SPECIFICALLY SET FORTH IN NI.COM'S TERMS OF USE (http://ni.com/legal/termsofuse/unitedstates/us/).