Acoustic noise contains valuable geophysical information

Dec 07, 2006

The proper processing of acoustic noise can provide a wealth of information. Geophysicists for example have used seismic background noise measurements to reconstruct the crustal structure under Southern California. The advantage of using existing acoustic noise is that signals only need to be recorded and not produced.

Researchers at TU Delft and the Colorado School of Mines have generalised the underlying theory and found that acoustic noise can be used for a much wider scale of physical applications than was previously thought possible. The researchers will publish their findings in Physical Review Letters on 8 December 2006.

As acoustic noise travels through a medium, such as the earth's crust, it compiles information. In recent years it was discovered that only a few simple processes (cross-correlation) were needed to extract a meaningful signal from acoustic noise. Geophysicists Kees Wapenaar and Evert Slob of TU Delft, and Roel Snieder of the Colorado School of Mines, have now developed a unified theory that extends the extraction of impulse responses from background noise for more general situations.

This theory includes electromagnetic noise in conducting media, acoustic noise in flowing and viscous media, and even diffusive transport phenomena. Moreover, the theory predicts that coupled processes, such as seismo-electric effect and the associated electrokinetic reflections, can also be retrieved from the background noise measurements.

It appears that background noise contains more information than one could possibly dream of several years ago. The theory can be used for 'remote sensing without a source' for a wide range of physical applications that include the determination of parameters of flowing media, viscous media, as well as the electrokinetic coupling parameters of porous reservoir rock. In partnership with Shell, the researchers have since created seismic reflection data from background noise that was recorded in a desert in the Middle East. Moreover, they expect their research methods to be applied in, for example, the LOFAR-project.

Source: Delft University of Technology

Explore further: What is Nothing?

add to favorites email to friend print save as pdf

Related Stories

The science of stadium sound

Sep 04, 2013

Football fans attending BYU home games the last two seasons may have noticed a few students roving through the crowd, giving their full attention to hand-held scientific instruments instead of the game.

Founder of US-based Bose audio firm dies at 83

Jul 12, 2013

Acoustics pioneer Amar Bose, founder and chairman of the audio technology company Bose Corp., known for the rich sound of its small tabletop radios and its noise-canceling headphones popular among frequent ...

Hearing the telltale sounds of dangerous chemicals

Aug 14, 2012

To warn of chemical attacks and help save lives, it's vital to quickly determine if even trace levels of potentially deadly chemicals—such as the nerve gas sarin and other odorless, colorless agents—are ...

Recommended for you

What is Nothing?

13 hours ago

Is there any place in the Universe where there's truly nothing? Consider the gaps between stars and galaxies? Or the gaps between atoms? What are the properties of nothing?

On the hunt for dark matter

15 hours ago

New University of Adelaide Future Fellow Dr Martin White is starting a research project that has the potential to redirect the experiments of thousands of physicists around the world who are trying to identify the nature ...

Water window imaging opportunity

Aug 21, 2014

Ever heard of the water window? It consists of radiations in the 3.3 to 4.4 nanometre range, which are not absorbed by the water in biological tissues. New theoretical findings show that it is possible to ...

User comments : 0