Microstar Laboratories PR - High-Resolution 1/3 Octave Analysis


Bellevue, WA, -- Microstar Laboratories, Inc., maker of Data Acquisition Processor (DAP) systems for PC-based high-performance measurement applications, has released a software package for audio analysis, for use with its xDAP systems. Using this package with just two extra lines of configuration script adds high-precision 1/3 octave analysis to your measurement application. In effect, your general-purpose xDAP system is transformed into a specialized audio analyzer instrument. This package is available for free download from the company's web site. It includes a technical note explaining how to customize the software to optimize individual applications. You can send the octave analysis results to the PC application environment of your choice.

A 1/3 octave analysis partitions a power spectrum into logarithmically-spaced frequency bands, corresponding to the manner that audio tones are perceived. There are alternative solutions for doing this, with various tradeoffs in capability and price. Single-purpose dedicated instruments do an excellent analysis, but building a good instrument is very challenging, and costs are high. GUI-based analytical software systems offer signal processing toolkits that can perform a similar analysis, but this too is very expensive, and ties the application inextricably to a high-overhead software environment. The solution of using an xDAP system and this free configuration software results in a streamlined system with high performance, low net cost, and compatibility with any software environment you want.

The embedded 1/3 octave analysis uses the MIXRFFT processing command - part of the DAPL 3000 operating system - for its frequency analysis. Processing the full audio range, ANSI band 10 (from 8.7 Hz) to ANSI band 44 (to 22.7 kHz), requires very large data sets. The MIXRFFT command supports this processing, with high precision. The special THIRDOCT analysis then does the "bookkeeping" to identify and summarize the logarithmically-spaced 1/3 octave bands. The technical note explains how to coordinate the data capture, classic frequency analysis, and 1/3 octave analysis activities.

The resolution of the 1/3 octave analysis is extremely high. This differs from behaviors you would get from typical "reference implementation" instruments using 6th-order bandpass filters (or their digital equivalents). This means that a signal registering as a crisp single band in the high-precision analysis would appear as a "multi-band smear" in a traditional instrument. If it is necessary to match such traditional behaviors, supplemental processing to distribute the high resolution spectrum results into neighboring bands is possible. Other supplemental processing could convert the results to RMS amplitude, dB gain, or physical power units.

DAPL Environment

The DAPL 3000 operating system and an xDAP measurement system provide the environment where embedded 1/3 octave preprocessing can run. Within that environment, the special processing operates much the same as ordinary data acquisition or control processing. When offloaded from the host system, complex number crunching operations do not burden orderly processing within host applications, making the applications easier to build.

Though multiple DAP boards can work together for large scale applications, octave analysis applications will seldom need that much processing power, and one xDAP system working alone can provide audio spectrum analysis on eight or more full-range audio channels simultaneously. The xDAP configuration is assisted by DAPstudio software. DAPstudio can display spectrum data "in real time," while simultaneously logging results. This alone might be sufficient for data recording and display applications.

Conclusion

A new THIRDOCT processing command, working in conjunction with MIXRFFT processing provided in the DAPL 3000 system, can add rigorous 1/3 octave analysis measurements to your applications - and it is almost as easy as capturing raw signal data. You need to add only one supplementary module with the special THIRDOCT processing command. No additional "software toolkits" are required. No redistribution or deployment charges. With the intensive numerical preprocessing offloaded to the Data Acquisition Processor system, just the required spectrum results are returned - minimal overhead, no logged raw data sets to manage, and results that are ready-to-use in automated test software.
The THIRDOCT processing command is a no-charge add-on for an xDAP system. Contact Microstar Laboratories for more information and to ask about the availability of evaluation hardware.

Additional Resources
  • The special module containing the THIRDOCT command is available for download from the Microstar Laboratories Web site. The download includes full documentation for the command.

    http://www.mstarlabs.com/ftp/modules.html
  • The download also contains documentation describing how to configure the processing of the MIXRFFT and THIRDOCT commands, with background information on methodology and customization. Or read the documentation online.
    www.mstarlabs.com/docs/tn257.html
  • Review full details about using the MIXRFFT command for general-purpose FFT processing in DAPL 3000 Command Supplement for xDAP.
    www.mstarlabs.com/docs/manuals/SUPPXDAP.PDF
  • Learn more about xDAP measurement systems.

    http://www.mstarlabs.com/daq-usb/xdap.html

    Editorial Overview

    New audio analysis software, available for download, can configure an xDAP measurement system to perform a rigorous and cost-effective 1/3 octave analysis. Adding this capability to a measurement configuration requires two lines of configuration script, lines that coordinate the DAPL 3000 system MIXRFFT command that performs the frequency analysis and the special THIRDOCT command that analyzes standard-defined 1/3 octave bands. Using the generic capabilities of high-performance Data Acquisition Processor systems rather than specialized instrument electronics or complicated software toolkits keeps costs low, and software applications simple. The high-resolution band separation and direct displays of signal power might be unfamiliar, but supplemental processing can be configured to further adapt the results to a more familiar form. The configured xDAP system can serve as a simple input device, with embedded smart processing, or as an interconnected device for complete audio testing.

    Microstar Laboratories, Inc. claims Microstar Laboratories, Data Acquisition Processor, DAP, xDAP, xDAP 7400, DAPL, DAPL 2000, DAPL 3000 and DAPstudio as trademarks. Microsoft has registered Windows as a trademark. Other organizations may claim - or may have registered as trademarks - other trade names, logos, and service marks that appear in this document but not in the list above.

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