| 1. |
- Claesson, Ingvar, et al.
(author)
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Adaptive Active Control of Machine-Tool Vibration In a Lathe
- 1998
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In: International Journal of Acoustics and Vibration. - 1027-5851 .- 2415-1408. ; 3:4, s. 155-162
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Journal article (peer-reviewed)abstract
- In the turning operation the relative dynamic motion between cutting tool and workpiece, or vibration, is a frequent problem, which affects the result of the machining, and in particular, the surface finish. Tool life is also influenced by vibration. Noise in the working environment frequently occurs as a result of dynamic motion between the cutting tool and the workpiece. With proper machine design, i.e. improved stiffness of the machine structure, the problem of relative dynamic motion between cutting tool and workpiece may be partially solved. However, by active control of machine-tool vibration, a further reduction of the dynamic motion between cutting tool and workpiece can be achieved. It was found that adaptive feedback control of tool vibration in the cutting speed direction, based on the filtered-x LMS-algorithm, enables a reduction in vibration, by up to 40 dB at 1.5 kHz, and by approximately 40 dB at 3 kHz. It was also observed that the introduction of leakage in the filtered-x LMS-algorithm improved the stability properties of the feedback control system. A significant improvement in the workpiece surface was observed and a substantial improvement in the acoustic noise level was obtained with adaptive control.
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| 2. |
- Claesson, Ingvar, et al.
(author)
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GSM TDMA Frame Rate Internal Active Noise Cancellation
- 2003
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In: International Journal of Acoustics and Vibration. - : Int. Inst. Acoustics and Vibration, USA. - 1027-5851 .- 2415-1408. ; 8:3, s. 159-166
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Journal article (peer-reviewed)abstract
- A common problem in the world's most widely-used cellular telephone system, the GSM system, is the interfering signal generated by the switching nature of TDMA cellular telephony in handheld and other terminals. Signals are sent as chunks of data, speech frames, equivalent to 160 samples of data corresponding to 20 ms at sampling rate of 8 kHz. This paper describes a study of two different software solutions designed to suppress such interference internally in the mobile handset. The methods are 1) notch filtering, which is multiplicative in frequency, and 2) subtractive noise cancellation, which is an alternative method employing correlators. The latter solution is a straigtforward, although somewhat unorthodox, application of "in-wire" active noise control. Since subtraction is performed directly in the time domain, and we have access to the state of the mobile, it is also possible to consider a recurring pause in the interference caused by the idle frame in the transmission, when the mobile listens to other base stations communicating. More complex control algorithms, based on the state of the communication between the handset and the base station, can be utilised.
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| 3. |
- Feng, Leping, et al.
(author)
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On application of radiation loss factor in the prediction of sound transmission loss of a honeycomb panel
- 2012
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In: International Journal of Acoustics and Vibration. - 1027-5851 .- 2415-1408. ; 17:1, s. 47-51
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Journal article (peer-reviewed)abstract
- The application of the radiation loss factor in the prediction of sound transmission loss of a lightweight, orthotropic sandwich panel is investigated in this paper. Comparisons with measurements show that predictions often underestimate the sound transmission loss of the panel around the corresponding critical frequency when the measured loss factor, which in principle includes the radiation loss factor, is used. This is due to the measurement methods used for the loss factor and the band average. It is thus recommended to use the loss factor measured at low frequencies plus the theoretical radiation loss factor in order to improve the prediction of the sound transmission loss of a honeycomb panel around the critical frequency.
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| 4. |
- Frenne, Nicklas, et al.
(author)
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Sound Source Characterisation and Transfer Path Analysis with Time Histories
- 2003
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In: International Journal of Acoustics and Vibration. - : International Institute of Acoustics and Vibration (IIAV). - 1027-5851 .- 2415-1408. ; 8:3, s. 167-175
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Journal article (peer-reviewed)abstract
- The article describes a method to separate time histories of partial sound sources. The goal is to develop a noise control engineering tool for use in sound quality improvement applications. Contributions from partial sound sources are identified. The partial sound sources may be ranked for the purpose of creating a better mixture of sound in selected listening positions. The strategy is to reproduce time histories of sources of importance. The method described includes experimental and calculation parts. The experimental part consists of the recording of sound pressure time signals, reciprocal measurement of frequency response functions, and source strength esti- mation of partial sound sources. The calculation part comprises calculation of the cross-spectral matrix of source strength, calculation of filters, and filtered sound pressure recording to obtain time signals of the individual sources. Usually the contribution from partial sources is impossible to record directly. In this laboratory experi- ment, such control was possible. The laboratory experiment shows that the method described makes it possible to produce informative separation of time histories of partial sound sources. The effects of the errors in the cal- culated time histories are audible but not pronounced.
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| 5. |
- Henriksson, Mats
(author)
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Analysis of Gear Noise and Dynamic Transmission Error Using a Recursive Kalman Filter Algorithm
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In: International Journal of Acoustics and Vibration. - 1027-5851 .- 2415-1408.
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Journal article (other academic/artistic)abstract
- Measurements of dynamic transmission error (DTE) and gear noise have been usedto investigate the relation between DTE and noise. A Kalman filter order trackingmethod was used to calculate the amplitudes of the gear mesh orders. The DTE showsnon-linear behaviour with rotating speed , which decreases as the torque is increased.There seems to be a linear relationship between noise and DTE for the higher torquesmeasured. This indicates that for the higher torques measured, a linear model can beused to predict the dynamic behaviour of the gear system.
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| 6. |
- Henriksson, Mats, et al.
(author)
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On Transmission Error, Shuttling Forces and Friction Forces as Gear Noise Excitation
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In: International Journal of Acoustics and Vibration. - 1027-5851 .- 2415-1408.
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Journal article (other academic/artistic)abstract
- Traditionally, transmission error (TE) has been used to asses the noise propertiesof gears. Measurements of gear noise for a complete truck gearbox have been used tocorrelate noise from a gear pair with calculated static transmission error, shuttling forceand friction forces. Two gear pairs with very similar macro geometry but differentmicro geometry was used. The measurement results show that there is a limitationif transmission error is considered as the only excitation mechanism when designingquiet gears. Often TE is multiplied with the gear mesh stiffness in order to calculatean excitation force. For gear not operating above the critical gear mesh resonance,this often overestimates the importance of TE, thus underestimating the importance ofother sources such as shuttling and friction forces.
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| 7. |
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| 8. |
- Johansson, Sven, et al.
(author)
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Active Control of Lateral Vibrations in a Railway Carriage
- 2002
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In: International Journal of Acoustics and Vibration. - : Int.Inst. of Acoustics and Vibration(IIAV). - 1027-5851 .- 2415-1408. ; 7:4, s. 195-210
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Journal article (peer-reviewed)abstract
- As trains are continually designed for higher and higher speeds the problems of railway carriage vibration are on the increase. Lateral vibrations in a railway carriage are noticeable to passengers if the vibration frequencies are lower than approximately 20 Hz. Below this frequency discomfort is a common problem for the passengers and below approximately 1 Hz motion sickness is a problem. The passive solution of stiffening the carriage chassis to shift the vibrational frequencies higher up results in inflated manufacturing and running costs, and opposes higher travel speeds due to increased weight. Semi-passive solutions such as modifying the structural dynamics of the carriage body by decoupling heavy underfloor equipment do not reduce the vibrations sufficiently. However, by appending a multi-reference feedforward active vibration control system, one way expect a substantial reduction in the lateral vibration level. Using a dynamic computer model of a railway carriage simulating the lateral vibration, and using as input bogie acceleration data measured on a running train, multiple-input/single-output coherence spectra were shown to constitute a suitable set of reference signals for an active control system. Control simulations based on the Feedforward Multiple-Input/Single-Output Filtered-x LMS Algorithm are carried out using different reference signal combinations. The control results indicate lateral vibration attenuation on the order of 15dB at the objective frequency of 10Hz.
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| 9. |
- Johansson, Sven, et al.
(author)
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Comparison of Multiple- and Single-Reference MIMO Active Noise Control Approaches Using Data Measured in a Dornier 328 Aircraft
- 2000
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In: International Journal of Acoustics and Vibration. - : Int. Inst. of Acoustics and Vibration (IIAV). - 1027-5851 .- 2415-1408. ; 5:4, s. 77-88
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Journal article (peer-reviewed)abstract
- In many applications of noise control, the greatest annoyance is caused by periodic low frequency noise. Successful reduction of such noise can often be achieved by using an active noise control system with narrowband feedforward control. If several noise sources contribute to the sound field, a multiple-reference control system is usually required. This type of system allows the reference signals from each noise source to be processed individually within the controller, thereby enabling individual control of the sound field from each noise source. The present paper addresses the problem of controlling noise from two sources that are more or less synchronized. A typical application is the control of propeller-generated noise within a twin propeller aircraft. To find out whether a multiple-reference controller is necessary, or if a single-reference controller is sufficient, the performance of a single- versus twin-reference control algorithm is evaluated in a comparative study. The study is performed as a computer simulation (off-line evaluation) using real-life data recorded in a Dornier 328 under different flight conditions. The results demonstrate that the twin-reference controller performs better than the single-reference whenever there is a slight deviation in the rotational speed of the two propellers. The paper also treats the generation of reference signals. The approach presented is based on a fixed sampling rate and uses a sliding FFT filtering technique.
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| 10. |
- Larsson, Martin, et al.
(author)
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A Module Based Active Noise Control System for Ventilation Systems, Part I : Influence of Measurement Noise on the Performance and Convergence of the Filtered-x LMS Algorithm
- 2009
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In: International Journal of Acoustics and Vibration. - : International Institute of Acoustics and Vibration. - 1027-5851 .- 2415-1408. ; 14:4, s. 188-195
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Journal article (peer-reviewed)abstract
- Low noise level is an essential feature when installing ventilation systems today. To achieve attenuation over a broad frequency range, the passive silencers traditionally used to attenuate ventilation noise can be combined with an active noise control (ANC) system. To insure reliable operation and desirable levels of attenuation when applying ANC to duct noise, it is highly important to be able to suppress the contamination of the microphone signals due to the turbulent pressure fluctuations arising as the microphones are exposed to the airflow in the duct. This paper is the first in a series of two, that treats the problem of turbulence induced noise originating from the airflow inside the ducts. Part I is concerned with theoretical and experimental investigations of the influence of the turbulence induced noise on the adaptive algorithm in the ANC system. Part II is concerned with design and investigations of microphone installations for turbulence suppression and results concerning the performance of an ANC system with the different microphone installations are presented. Some of the results were obtained at an acoustic laboratory according to an ISO-standard. The attenuation achieved with ANC was approximately 15-25 dB between 50-315 Hz even for airflow speeds up to 20 m/s.
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