Aero & Defense
Wing flutter is a nice example on how critical vibration can be to aircraft. It is well controlled today, in wing design and setting the limits on allowable maximum airspeed.
There is a range vibration and noise issues in- and around aircraft and flight defense. From aero engine unbalance, acoustic fatigue, over cabin ventilation noise, to precision guidance , the list is much longer.
With rigorous safety requirements any new standardized noise/vibration testing procedure on civilian aircraft takes a long time to reach acceptance. Today all major aircraft manufacturers in the world already have Qsources equipment In their research and development. Exciting landing gears, cabin acoustics, components, new carbon structures, etc. Because the measurements with the volume sound sources or with the self aligning and self suspending shakers, because they are more accurate on light weight structures, because of more reliable results with less dependence of the measurement technicians, or because the in no alternative that fits in the small space where excitation is needed.
The efficiency, accuracy and small size of the Qsources sound sources and shakers helps to ensure the safety, reliability, and performance of aeronautics and flight defense systems.
Some applications
Landing gear modal analysis
To control shimmy, tire and component wear the modes of landing gear are analyzed in detail. This is largely done using numerical using kinematics and FE models. But there is need for model correlation tests and measurement of bearings and other interfaces to improve the numerical models. The efficiency and accuracy of the measurements is much improved by the use of the self-supporting Qsources shakers. Some shakers for such application from high to lower force level:
Speech intelligibility
It is sometimes a miracle how flight personnel manages to understand what passengers are saying and the other way around too.
Noise controle in the medium and higher frequencies is the first objective to achieve comfort and speech intelligibility. Working on isolation of boundary layer noise across the fuselage panels, window build-up, but also sealing doors, and controlling the noise from bleed air used for ventilation. The Qsources volume sources for accurate meausrement of isolation/acoustic transfer functions:
To optimize in-cabin acoustics for better speech intelligibility and better performance of the audio system other sound sources can be used. To measure reverberation, impulse responses, STI, transfer etc:
Low frequency cabin noise
In-flight booming noise due to engine-rotor unbalance, or propeller blade passage can a mayor contributor to fatigue of flight personnel and passengers. It can even be level determining and influence delivery acceptance by airlines. This is not only about controlling for example the aero-engine unbalance, which has limits. The vibro-acoustic sensitivity of the engine consoles, fuselage structure and panels needs to be known and controlled. Using reciprocity allows non-intrusive testing on complete aircraft. No need for attachment of shakers near consoles or opening up of the cowlings to have access for shaker or instrumented hammers. With a double sided tape and small accelerometers near various critical locations of engine consoles or landing gear, APU mounting, etc. This way efficient and well reproducing measurements of vibro-acoustic sensitivity are possible.
Panels and other light weight components
Hatches, cowlings, nose cones, cabin luggage trays, instrument panels, everywhere some mass saving is possible. Numerical models indicate how to design the lighter structures, using carbon and more complex shapes to save weight and maintain critical stiffness/strength. And measurements verify the numerical models, and allow them to improve. Some shakers for light weight structures of smaller and medium size:
All described measurements also require software and sensors, of which several are available in the market. Depending on the exact application our partners,
Siemens, Polytec, Head acoustics
all propose leading full chain solution including the Qsources excitation sources and shakers
