Vibration Control of Joist Framed Floors Using Tuned Mass Dampers

vibration-controlDEICON was called upon to develop a tuned damping solution to mitigate floor vibrations across a variety of rooms inside an educational facility. The make-up of the impacted floors was concrete on metal deck, supported by open-web bar joists. The floors came in various sizes and shapes (rectangular, trapezoidal, and irregular), with the first resonant frequencies in the 6.5-7.5 Hz range.

DEICON designed and fabricated tuned mass dampers (TMDs) to address the vibration challenges with the floors. The TMDs were tuned to the natural frequencies of the first vibration modes of the floors they were designed for. The tuned mass dampers added substantial damping to the floors bringing their vibration to acceptable levels. More

 
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Combustion Instability Mitigation

The combustion instability (thermoacoustic instability) of a gas-fired combustor with a low-frequency instability occurring at 100 Hz, was successfully mitigated using DEICON’s passive acoustic radiation based tuned absorber (damping system). Contrary to the more traditional tuned acoustic absorbers (perforated liners, quarter wave tubes, etc.) that are objectionably large at such low frequencies, DEICON’s passive acoustic radiators are small in size and highly effective in providing tuned acoustic damping at low frequencies. In applications that the unstable frequency varies with time, depending on the operating conditions of the combustion system, DEICON promotes active acoustic damping solutions. More

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Balcony Floor Vibration Abatement Using Tuned Mass Dampers

Excessive vibration of three large balconies in a performing art center were dampened using tuned mass dampers (TMDs). Nine TMDs were designed and built for the three balconies (three/balcony) and appended to the vibrating structure at locations where they can most effectively couple with the target mode(s).

The TMDs, tuned to the balcony resonant frequencies of 6 Hz and 9 Hz, added the required damping to the balconies to bring their vibration to acceptable levels. More

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Active Feedback-Controlled Boom Noise Damping/Absorption in Large Vehicles

Large vehicles, such as SUVs (Sport Utility Vehicle) and minivans, exhibit body boom phenomena during multiple source excitation events including rough road/impact and powertrain induced events. The main cause of the boom is the low-frequency acoustic/vibro-acoustic modes of the cavity being excited via the high acoustic transfer functions at multiple paths, due to an inherently weak body structure and/or existence of popular features such as tailgates with their corresponding dynamics. Abating the boom noise by modifying the response is the more viable and less costly option than body changes.

DEICON’s active acoustic damping/absorption system has been used successfully to do such modification, cost-effectively. More

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Vibration Isolation of Large Transformers

In a recent application, DEICON was asked to further improve the structure-borne noise reduction of two large transformers (9000 pounds, each) installed in a multi-story residential building. The transformers were housed in sound proofed rooms and isolated from the floor via mounts (compressed fiberglass mounts for one transformer and cork/neoprene mats for the other). In a preliminary study including some laboratory tests it was concluded that the compressed fiberglass mounts had too much damping deteriorating their high frequency vibration isolation and the cork/neoprene mounts were too stiff to effectively isolate the transformer. It was decided to change the isolation schemes from compressed fiberglass and cork/neoprene to air. More

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