| 1. |
- Johansson, Sven, et al.
(författare)
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ACTIVE CONTROL OF PROPELLER-INDUCED NOISE IN AN AIRCRAFT MOCK-UP
- 1999
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Konferensbidrag (refereegranskat)abstract
- A noisy environment dominated by low frequency noise can often be improved through the use of active noise control. This situation arises naturally in propeller aircraft where the propellers induce periodic low frequency noise inside the cabin. The overall interior sound pressure level inside a turboprop aircraft is typically rather high, and the passenger flight comfort could be improved considerably if this level was significantly reduced. This paper discusses the behaviour and robustness of a narrowband twin--reference feedforward active noise and vibration control system in a SAAB 340 mock-up. The resulting sound pressure level were recorded and is presented as the narrowband attenuation versus time. The spatial distribution of the sound pressure level is also presented. The results show that the twin-reference controller exhibits good performance with respect to attenuation and robustness for both stationary and non-stationary conditions.
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| 2. |
- Lagö, Thomas L, et al.
(författare)
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Active vibration reduction in a light high speed train bogie
- 1998
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Konferensbidrag (refereegranskat)abstract
- Vibration induced sound in the car of a light high speed train is of great interest since the light structure makes it more resonant. Low weight is important and and the aim is to decrease the weight of future trains significantly, compared to the X2000. Classical sound attenuation techniques are good for higher frequencies but active techniques are more suitable when lowering the low frequency induced noise in the car. This work therefore addresses a problem that is likely to occur in future trains, due to the decreased weight. The sleepers are a dominant excitation source for this case, and this implies a periodic excitation of 85 Hz when the train is running at 200 km/h. The sleeper frequency excitation will be an even larger problem when the car has a lower weight as well. This paper describes an active vibration isolation, or damping, where the goal is to reduce the sound inside the car due to the sleeper frequency excitation not the vibrations levels. Four actuators have been used and both an AVC as well as an ASAC control strategy has been tested and the results are presented. Tests have been performed on a full scale train in a lab as well as on track at approximately 200 km/h.
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| 3. |
- Persson, Per, et al.
(författare)
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Active Control of Sleeper-induced Sound in a High Speed Train
- 1999
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Konferensbidrag (refereegranskat)abstract
- Vibration-induced noise in train cars is an area that receives a great deal of interest at the moment. Due to economical and environmental issues, manufacturers are cutting the weight-budget for future trains to achieve a lower total life-cycle cost. This has a negative impact on the interior noise and passenger comfort and to be competitive new methods to reduce the negative side effect are sought. This paper describes an active control approach to isolating the car from bogie vibrations in such a way that the noise inside the car is reduced. An active control system with four inertial mass actuators fitted to an experimental light weight bogie were used to control bogie vibrations and noise inside the car. Several tests were performed in both a lab environment and on track at full speed.
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| 4. |
- Persson, Per, et al.
(författare)
-
Active vibration reduction in a light weight high speed train bogie
- 1999
-
Konferensbidrag (refereegranskat)abstract
- Vibration-induced noise in the car of train is of great interest since low weight is important, but makes the structure more resonant. One excitation source is the sleeper frequency which gives rise to a periodic excitation. This paper describes an approach to isolate the vibrations caused by the sleepers in such a way that the noise inside the cabin is reduced. An LMS algorithm with four inertial mass actuators fitted to the bogie with control microphones placed in the cabin. The tests were performed on an experimental light weight bogie fitted to a test car, in both lab environment and in full scale tests on track at full speed (200 km/h).
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