Volume 11, Number 3 • Fall 2003 • Advanced Technologies

HHT Revolutionizes Signal Analysis

Since 1965, scientists have used Fast Fourier Transform (FFT) to analyze periodic signals generated by mechanical systems. However, when natural/physical phenomena are involved—from heartbeats to acoustic and earthquake vibrations to waves and sea-surface temperatures—FFT falls short, unable to analyze accurately the chaotic and transient signals.

In the mid-1990s, NASA Goddard Space Flight Center innovator Dr. Norden Huang began developing a better method for analyzing data for NASA’s Earth Science Enterprise. Dr. Huang’s new algorithms, which combined the empirical mode decomposition method with the Hilbert transform method, accurately analyzed the time, frequency and energy data of physical signals. These algorithms—officially called the Computer Implemented Empirical Mode Decomposition Method, but better known as the Hilbert-Huang Transform (HHT)—revolutionized signal processing.

The HHT technology is a highly efficient, adaptive and user-friendly general computational method for analyzing data from physical signals. HHT offers improved accuracy and yields more meaningful results than with previous analysis tools, which tended to obscure or discard valuable information. The method can be used to conduct spectrum analysis of any physical signal—signals that, by their very nature, are nonlinear and nonstationary. Such signals are found in communications, sonar, seismic analysis, acoustics, optics and other applications.

By transforming the nonlinear and nonstationary signals into accurate frequency information, HHT opens up a whole new world of understanding—a world that previously was inaccessible via standard methods. Applications can be found in medicine—sensors, imaging, drug discovery and instruments; acoustics/vibration—analysis of highway noise, speech/sound and machine vibration; and industry—machine monitoring/failure prediction and electrical circuits. HHT also can be used to perform numerical simulation of fluid flow, nondestructive testing and shock loading of structures, environmental analysis and even analysis of economic and market data.

The revolutionary HHT method has been recognized as “one of the most important discoveries in the field of applied mathematics in NASA history,” as stated by NASA’s Inventions and Contributions Board in bestowing the technology and Dr. Huang with an Exceptional Space Act Award. HHT also won the 2002 NASA Government Invention of the Year Award. The technology has received recognition from the Federal Laboratory Consortium—2001 Award for Excellence in Technology Transfer; R&D Magazine—2001 R&D 100 Award; and Government Executive Magazine—1999 Government Technology Leadership Award.

HHT is now on the fast track to commercial use. In addition to its use in other NASA programs and projects, the HHT algorithms and the software program that implements them are available outside of NASA. Qualified users can download a 60-day trial version for testing and evaluation. Upon seeing how successfully HHT performs, users can license the software for ongoing use.

Early responses to HHT have been extremely favorable, and NASA Goddard Space Flight Center expects many more potential users to register their interest. So far, the HHT trial software has been distributed to more than a dozen government agencies, universities and commercial companies for testing and use in a wide range of applications, including acoustical data analysis, nondestructive evaluation and medical data analysis.

The future for HHT in the commercial marketplace looks even brighter in the coming months. This fall, HHT will be featured at the 2003 National Association of Seed and Venture Funds conference, held November 2–5 at the Wyndham Inner Harbor Hotel in Baltimore, MD. In keeping with the conference theme of “Innovations in Early Stage Investing,” HHT will be presented and discussed during a panel focusing on investing in platform technologies. (See http://www.nasvf.org for more information on the conference.) *

More information on HHT, its benefits, its applications and how to license it is available at http://techtransfer.gsfc.nasa.gov/HHT/HHT.htm. Please mention you read about it in Innovation.

NASA Official: Jonathan Root • Web Design: Printing & Design Office, NASA Headquarters • Credits