Portable Laboratory for Capture, Analysis, and Playback of Infrasonic Animal Vocalizations

Author(s):
Bart Craft - MicroCraft Corporation

Industry:
Research

Products:
Signal Conditioning, LabVIEW

The Challenge:
Creating a portable, flexible, easy-to-use data acquisition system to facilitate research in the field of animal bioacoustics.

The Solution:
Using the waveform datatype and analysis functions of LabVIEW 6i and the LabVIEW Sound and Vibration and Signal Processing toolsets to create the bioacoustics research system.

Background
On March 2, 2000, MicroCraft Corporation received an excited call from Elizabeth von Muggenthaler of the Fauna Communications Research Institute (FCRI) in Hillsborough, North Carolina. She had just received a graciously donated copy of National Instruments LabVIEW 5.1 and a DAQCard 1200 from National Instruments and was hoping to have it up and running during an important interview the following day. The Arts and Entertainment Television Network (A&E) was going to highlight her research on infrasonic animal communication in a segment of a documentary they were filming. National Instruments referred her to its Select Integrator in the area, MicroCraft. MicroCraft helped her fashion a breakout assembly for her microphones and gave her a quick tour of the many pre -built solutions that are included in LabVIEW. She settled on a spectrum analyzer, took a swipe at it with the coloring tool, and went home relieved. The interview was a success, and the documentary aired the following August.

The Program
The FCRI bioacoustics research system user interface is divided into three general areas. One is dedicated to live monitoring of the microphone input. The other two are concerned with the capture and analysis of events within the live data stream. Tip strips are used throughout the interface to assist the user.

The top of the LabVIEW screen contains the menu bar and two real-time data displays - a time domain chart and a frequency domain graph. The primary menu functions select which input or output to use and control the sample rate of the input. The chart displays scrolling amplitude data versus time, and the graph is a continuously updated auto power spectrum of the amplitude data.

The middle of the screen contains a control used to take a snapshot of the live data and a graph to display that data. This graph has two vertical cursors that are used to mark the beginning and end of significant events to analyze or copy to the manipulation area of the screen. In practice the researcher watches the real-time time domain chart for an event then clicks the snapshot control while the event is scrolling through the display. This action transfers the contents of the time domain chart buffer into the snapshot graph. The researcher then uses the graph cursors to further isolate the event.

The bottom of the LabVIEW screen is implemented as a tabbed control to conserve screen real estate and to provide logical grouping of the analysis and manipulation functions. The first tab, labeled 1D, performs a fast Fourier transform (FFT) power spectrum on the data between the snapshot graph cursors. The second tab, 2D, performs a short-time Fourier transform (STFT) on the data between the snapshot graph cursors. The display of this spectrograph is an intensity graph where time is in X, frequency in Y, and magnitude in Z. The data is represented visually as color variations through a predefined color palette. The STFT is rather processor intensive, so live data acquisition and display is suspended for a few seconds during this operation.

The third and final LabVIEW tab, misc, contains another graph, called the workspace, with two cursors and a number of buttons used to manipulate the data in the workspace. The researcher can copy data from the snapshot graph, copy and paste data within the workspace, delete portions of the workspace data, or clear the graph entirely. A filter can be applied to the workspace data. This filter is configured in a pop-up window and an FFT can be perfo rmed to observe the results. This FFT is displayed in the graph on the 1D tab. The workspace data can be saved to a standard WAV file. Finally, the data can be played back through the PC sound card or routed to an amplifier through one of the analog outputs of the data acquisition device. The playback speed can be manipulated to enhance low frequencies.

Current Research
The A&E documentary "When Animals Talk" highlighted the Institute’s research with giraffes. Since then, the program has been used in studies involving the nearly extinct Sumatran Rhinoceros, elephants, tigers, and a number of other big cats. Another researcher plans to use it in the summer of 2002 off the coast of Newfoundland in a study of the Beluga Whale.

Summary
The program has recently been named Polynesia in honor of the parrot that taught Dr. Dolittle to talk to the animals. Currently work is being done to make the entire application based on the configuration capabilities of NI Measurement & Automation Explorer. This will provide the flexibility required by the various microphones and other transducers used in this type of research. Work with FCRI has been and continues to be very rewarding. It is well on its way to becoming a world -class tool for bioacoustics research. Polynesia will be made available to other research efforts some time in 2002.

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