MSI-DFAT

The power of creative thinking lies in transforming the mundane into something extraordinary.

For Bob Goldstein, the founder of Maryland Sound International (MSI), this adage became a reality when NASA and Orbital Sciences Corporation approached him in 1998 to provide an alternative to traditional reverb chambers used for acoustic testing of spacecraft and satellites. The reason? These chambers were extremely expensive to build, run and maintain, and their distant locations from manufacturers often presents logistical challenges. Companies face substantial costs and risks when shipping expensive and mission-critical spacecraft or satellites to distant test facilities—or, even when handling and moving a sensitive and delicate spacecraft from one test bay to the room right next door.

MSI pioneered the solution to this predicament. Having designed sound systems for the entertainment industry, the company was already well-versed in the science of acoustics, as well as the complex logistics of running live sound systems. Leveraging this core expertise, MSI conducted an initial experiment to ensure that satellites housed in a rocket’s fairing could survive the extreme vibrations caused by launch noise, which can exceed 150 decibels (dB). The first few acoustic tests worked well enough with simple commercial loudspeakers and manual equalizers for Bob Goldstein to justify diving head-first into the business. Over the next decades—and after blowing up millions of dollars’ worth of commercial-off-the-shelf concert loudspeakers—the company focused into incrementally improving, designing, assembling, and manufacturing its own purpose-built Direct Field Acoustic Testing (DFAT^®) systems.

“Over the past two decades, we have now successfully acoustically tested nearly 230 spacecraft, a number that continues to steadily grow,” says Goldstein. “Our portable DFAT system enables troubleshooting and testing to be done right where the satellite is built, eliminating both the high costs and risks associated with any form of transportation,” he adds.

Recognizing the immense value this new approach could bring to space missions, MSI in 1999, invented DFAT (also known now as Direct Field Acoustic Noise Testing or ‘DFAN Testing’). MSI-DFAT is the world’s first company dedicated to providing state-of-the-art DFAT^® services and equipment.

MSI-DFAT: Incrementally Improving Acoustic Testing

The DFAT testing method overcomes many technical limitations of traditional reverberant chambers, such as creating both diffuse and non-diffuse sound fields. MSIDFAT’s purpose-built Noise Generation Systems (NGS) now makes DFAT even more efficient and effective—capable of replicating the specific acoustic signatures in a way that consistently amazes engineers and test specialists.

Through a massive tower of lightweight and structurally-stable loudspeakers, MSI-DFAT simulates the intense sound pressures and vibrations that satellites or spacecraft experience during launch. The signal produced by these loudspeakers is precisely generated and controlled by a narrowband multi input, multi-output Noise Control System (NCS), which acts similarly to an audio equalizer. The NCS monitors various microphone locations set around the loudspeakers and spacecraft, ensuring in real-time that the NGS generates sound pressure accurately matches the precise sound intensity and frequency profile the satellite encounters throughout the mission. During the test, the NCS continuously checks every 4-5 seconds and adjusts the loudspeaker signals in real time.

This approach helps in creating and controlling a wide range of acoustic fields within the test volume, unlike a reverb chamber where sound can only become uniform due to sound waves bouncing off of the walls.

A recent case study further highlights the benefits of MSI-DFAT’s modular and adaptable system that makes their acoustic testing seamlessly customizable and perform highly effectively. A spacecraft manufacturer once asked the company to conduct an acoustic test with very loud low-frequency sound. The test article was surrounded by 18 large subwoofer columns with only 6 smaller a whopping 140dB in the 100 Hertz (Hz) frequency band alone! By employing a design approach that separates loudspeakers according to their frequency ranges, the modularity and flexibility of MSI-DFAT’s NGS allowed the company to custom-tailor this setup, exactly meeting the client’s specific needs. This approach ensured optimal performance while avoiding any excess additional costs. In contrast, alternative design approaches of loudspeakers for DFAN testing instead cram all of the subwoofers and mid-to-high frequency speakers into the same cabinet box. This inferior design-approach results in excessively heavy, inflexible and non-modular loudspeaker setups where clients overpay for inferior results that under-deliver.

In another instance, a spacecraft’s hardware was responding very aggressively to the acoustic energy, shaking so intensely that MSI-DFAT had to halt the test with an emergency stop safety mechanism. However, MSI-DFAT used its proprietary ‘narrowband response limiting’ technology and processes to isolate and reduce the excessive excitation at only the specific harsh resonant frequency, preventing damage to the spacecraft while maintaining the overall required noise levels. The client was extremely grateful MSI-DFAT’s quick action and solution in addressing the issue, ensuring the spacecraft was safely prepared for launch while reducing physical testing risks.

The Pioneers of DFAT

A team of world-class specialists, now led by Dr. Alessandro “Alex” Carrella, is behind the scenes. The team at MSI-DFAT continually refines and advances DFAT technology and methods. Comprised of audio engineers and scientists with unrivaled decades of experience in spacecraft and satellite Assembly, Integration, and Testing (AI&T) they ease the burden of spacecraft manufacturers campaigns, while delivering exceptional, timely, and economically superior results. Beyond the company’s growth, they also are making significant strides in the scientific community through their continual dedication to R&D—innovating and improving upon the methods, theories and best practices for DFAT. For example, the MP™ series loudspeakers are specially-designed by Matthew Polk, founder of Polk Audio, who is a world-class electrodynamic loudspeaker designer and inventor. The first loudspeakers used by MSI-DFAT were high-end off-the-shelf loudspeakers and had extensive cabling, complex connections, and technical limitations (such as thermal compression) making the setup and operation complex. Over time, the company has since significantly improved upon the designs and performance of its loudspeakers, amplifiers, and related equipment to speed up, simplify, and improve the setup, operation and performance of their DFAT systems. MSI-DFAT’s system is now easy to use, simple to operate, and proven to be an effective alternative in terms of performance and economics, especially when compared to reverb chambers and other DFAN testing providers.

The MSI-DFAT team has launched over 230 acoustic tests since 1999, sharing knowledge both within the company and across the aerospace industry. With over 275 combined years of acoustic testing, the experience of the team at MSI-DFAT embodies Malcolm Gladwell’s ‘10,000 hours rule’, which asserts that it takes 10,000 hours to become world-class experts in a field.

“We have dedicated an immense amount of time doing one thing: DFAT. The commitment of our team is truly remarkable, and we have learned a lot ever since our first test in 1999.” says Goldstein.

“And the future is very bright. We are just getting started. It is only day one.” says Alex Carrella, CEO and VP of Strategy and Growth of MSI-DFAT.

Many team members have been with the company from the very beginning—an impressive accomplishment for MSIDFAT—while it continues to invest into its next generation of talented young engineers, technicians and business leaders. Through the combination of technical expertise, steady management and business stewardship, MSI-DFAT has evolved from building loudspeakers to becoming the backbone of many missions to outer space.

MSI-DFAT is a ray of hope for numerous spacecraft manufacturers who cannot afford any setbacks before launch. What was initiated as a means to amplify immersive experiences for entertainment has transformed the company into the go-to choice for safe, rapid, and economical acoustic qualification within Assembly, Integration and Testing (AI&T). MSI-DFAT is pushing the boundaries of technology and will continue to contribute to the overall safety and reliability of space missions far into the future.