An active boom noise control solution which can be viewed as a low-frequency ‘active tuned acoustic damper’ is developed to add acoustic damping to the low-frequency standing waves inside the cabin of a large SUV to quiet its tonal persistent boom noise. The existing stock 8 inch subwoofer as well as one of the […]
Read MoreProblem: Most rooms/cabins have dimensions that favor standing waves (resonant modes) which are in the range of vibration frequencies of the propulsion engines, gensets, or other machinery on board watercraft. undesirable and unfortunate coupling of the room acoustic modes with the machinery vibration frequencies results in boom/rumble in the room. such low-frequency noise, which is […]
Read MoreThe airframes of some airplanes are equipped with a number of tuned vibration absorbers tuned the propeller blade passage frequency, to cancel out the noise and vibration and keep the cabin quiet and comfortable. A number of the DVAs in a private airplane were removed from the airframe, disassembled and their leaf springs refurbished. Following […]
Read MoreThe performance of modern combustion systems including fuel efficiency, emissions, pattern factor, and lean flammability limit depend on the mixing process between the combustion air and the fuel. For proper mixing, modern combustors rely on a combination of large and small scale turbulent eddies and vortices to control mixing, fuel droplet dispersion (for liquid fuel), […]
Read MoreIn many noise control applications, the offending noise occurs only in a narrow range of frequencies or even at a single frequency. Noise generated by industrial machines/equipment mostly falls in this category. For such situations, it is possible to design a sound absorption system that is “tuned” to those target frequencies. One of the most […]
Read MoreIn some sound absorption applications, it is necessary to use more than one reactive absorbers (such as quarter-wave tubes or Helmholtz resonators) all tuned to the same frequency. Close placement of these resonators can have an adverse impact on their effectiveness. When such devices are placed along the direction of variation in the shape of […]
Read MoreLarge 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 […]
Read MoreReactive absorbers, such as Helmholtz resonators (HR) or quarter-wave tubes, are commonly used as the most effective solution for abating the low-frequency tonal noise in many applications including the quieting of air intake induction system noise in internal combustion engines. The problem with these low-frequency absorbers is their large size. In addition, reactive absorbers can […]
Read MoreA small room is used to evaluate how DEICON’s patented, active acoustic damping technology, ‘electronic bass trap’, enhances low-frequency musical articulation in that room The rectangular room has a dominant coloration due to the 32 Hz standing wave that shapes up along its length. Electronic bass trap is used to add damping to the first […]
Read MoreDEICON’s patented, feedback-controlled, electronic acoustic absorber is highly effective in reducing the boominess of sound at frequencies corresponding to offending (coloring) standing waves of an enclosed space. The controller which can be realized by a tunable, analog circuit or a high-speed micro-controller can be tuned to one or multiple low frequencies either to dampen the […]
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