| 1. |
Xun Wang, Takayuki Satake, Yosuke Koba, Satoshi Ishikawa, Shinya Kijimoto, Active reduction of the two-way diffraction from a noise barrier by using feedforward control, 45th International Congress and Exposition on Noise Control Engineering: Towards a Quieter Future, INTER-NOISE 2016
Proceedings of the INTER-NOISE 2016 - 45th International Congress and Exposition on Noise Control Engineering: Towards a Quieter Future, 576-586, 2016.08, This paper develops a feedforward (FF) structure based active noise control (ANC) system that reduces the two-way diffraction from an office partition with the aim of actively creating isolated acoustic domains in open-plan offices. The FF-ANC system can only reduce the noise downstream of the reference sensor due to the causality requirement. Therefore, a coupled FF control structure is proposed to realize the reduction of two-way diffraction. This system applies a two-source loudspeaker array as the control source, and two microphones as the reference and error sensors. The directivity of the loudspeaker array is controlled to emit the control sound only into the corresponding control area. In comparison with the preceding active diffraction reducing systems, using a directivity controlled loudspeaker array can generate an absorptive acoustic boundary rather than a reflective boundary on the diffracting edge, which can isolate the acoustic environment without adding reverberation in a room. The effectiveness of the proposed system is verified by computer simulations.. |
| 2. |
Xun Wang, Yousuke Koba, Satoshi Ishikawa, Shinya Kijimoto, Hybrid active noise barrier with sound masking in open-plan offices, Noise Control Engineering Journal, 10.3397/1/376389, 64, 3, 403-415, 2016.05, This paper presents a small-typed active noise barrier (ANB) with sound masking techniques for alleviating the noise problem and protecting the speech privacy in open-plan offices. This soundproof system reduces and masks the undesired sound simultaneously so that lower level of the masker is required to achieve the sound masking effect, comparing with the conventional sound masking systems. First, a real-time experiment to verify the noise attenuation performance of the proposed system for practical application has been conducted in a real office room. In the experiment, the influence of background noise on the system performance has also been investigated. The experiment results show that 3-8 dB active noise attenuation can be achieved behind the ANB in an office room. Moreover, in order to select an appropriate masker for the sound masking part of the system, several maskers have been compared and investigated by listening experiments. The results suggest that the stationary maskers are more suitable for the sound masking in offices by considering the sound masking performance and the annoyance of the maskers comprehensively.. |
| 3. |
Noise barrier using hybrid ANC system (Proposal and application of an adaptive robust feedback ANC system)
In this paper, an adaptive robust feedback (FB) active noise control (ANC) system is proposed and applied to the previously developed active noise barrier (ANB) using a hybrid (HB) ANC system, which aims to relieve the indoor noise problem. The FB control is preferred for this small-typed ANB application because only error sensor is required for the FB control system so that a compact controller can be easily realized. In practice, however, the robust stability of the FB controller must be considered. Moreover, the waterbed effect of the FB control will cause noise enhancement at some frequencies out of the target band of control. In order to design a robust controller with limited noise enhancement in real-time control, a modified frequency domain block LMS (modified FDB-LMS, MFDB-LMS) algorithm, which has the reduced computation complexity and the same steady-state performance comparing with the conventional FDB-LMS algorithm, is proposed in this paper, firstly, owing to the easiness to verify the robust stability and the noise enhancement constraints in the frequency domain adaptive process. Then, an internal model control (IMC) typed FB-ANC system exploiting the MFDB-LMS algorithm, into which the constraints to guarantee the robust stability and limit the noise enhancement to within a given value has been integrated, is proposed and applied to the ANB. The effectiveness of the proposed FB-ANC system and the noise attenuation performance of the ANB using the proposed system have been validated by simulations.. |
| 4. |
Noise barrier using hybrid ANC system (Supression of the noise enhancement caused by the waterbed effect and investigation of the noise attenuation performace under various sound field configurations)
In this paper, the hybrid active noise control (HB-ANC) system applied in the active noise barrier (ANB) is improved, and the noise attenuation performace of the ANB is invetigated under four different sound field configurations. This hybird ANB reduces the diffraction noise from top of the ANB and the noise propagated to the head position of the target person behind the ANB simultaneously to achieve higher noise attenuation. However, the waterbed effect of the feedback control part of the HB-ANC system will cause noise enhancement at some frequencies in the control area. In order to solve this problem, the HB-ANC system is improved by adding a filter to cancel the noise enhancement caused by the waterbed effect. Then, the noise attenuation performance of the hybrid ANB under four sound field configurations is evaluated by simulations. The sound field configurations are set up to investigate how the diffraction from side of the ANB and the reflection influence the performance of the ANB. An experiment in the anechoic chamber is also conducted. The results indicate that the low frequency noise attenuation can be obtained in a wide area behind the ANB, and at the head position of the person, the noise attenuation can be ensured within a wider frequency range, even for the sound fields where the uncontrolled diffraction from side and the reflection exist.. |
| 5. |
A noise barrier using hybrid ANC system
In this paper, in order to improve the low frequency noise insulation performance of a noise barrier, a new type of hybrid active noise control (ANC) system is proposed. The proposed system is a combination of feedforward and feedback controller. The reference signal for the feedforward controller is generated in the feedback part, so the reference microphone is not necessary. The feedback controller is used for controlling the acoustic boundary to insulate the diffraction noise, and the feedforward controller is used for reducing the noise at the error microphone which is set to be near the ears of people. As a preliminary work, this paper validated the effectiveness of the proposed ANC system both by simulations and by an experiment. The result shows that the active noise insulation provided by feedback controller and the noise attenuation provided by feedforward controller accumulated in the control area, so that the proposed ANC system has better control performance than individual feedforward or feedback ANC system.. |
| 6. |
Two-Dimensional Acoustic Analysis by Concentrated Mass Model
FDTD method and CIP method are used for an acoustic analysis in time domain. However, these methods do not take into account a sound attenuation from viscosity. In our study, we propose a concentrated mass model which consists of spring-mass-damper system to perform a two-dimensional acoustic analysis. The dampers of this model consider viscosity of air. In this paper, we derive mass, connecting springs, and connecting dampers. The characteristic of connecting spring is derived from the condition of adiabatic change of air, and the connecting damper is derived from the normal stress. To confirm the validity of the proposed model, the numerical results obtained by the concentrated mass model are compared with the theoretical value of a traveling wave, and with the theoretical value of the natural frequency. All numerical computational results agree very well with the theoretical values. Therefore, it is concluded that the proposed model is valid for the two-dimensional acoustic analysis.. |
| 7. |
Yoshiko Ohno, Yosuke Koba, ISHIKAWA Satoshi, Shinya Kijimoto, ACTIVE NOISE CONTROL FOR A MOVING EVALUATION POINT USING STEPSIZE VECTOR AND SECONDARY PATH INTERPOLATION, MJIIT-JUC Joint Symposium 2012, 2012.11. |
| 8. |
Active Noise Control for a Moving Evaluation Point Using Stepsize Vector
In three-dimension acoustic field, it is difficult to control in the whole room using active noise control (ANC) technique. Instead, around-head-control is investigated in this paper. By using around-head-control method, an object person can get the noise reduction effect without controlling in the whole space, because it makes around the head quiet locally. Therefore, to realize around-head-control, it is necessary for a controller to follow the head movement. However, there is a problem that the control effect under the movement is worse, and the recovery of control effect after movement is slow by conventional ANC. Against this problem, we propose the new method of improving the adaptation speed when an evaluation point moves. In the algorithm, the updating size appropriate to each coefficient of the adaptive filter is calculated by using a step size vector. The step size vector is calculated from the coefficient of adaptive filter before updating. The validity of the proposal method is shown by the numerical simulation and the experiment in an anechoic chamber.. |
| 9. |
Active Control against Impact Noise Using Frequency Domain Adaptive Algorithm
Noise control has been developed to establish the comfortable soundscape even if our house life. Floor impact noise such as the sound of footsteps or falling object becomes a problem in an apartment house. Floor impact noise has a peak at the low-frequency range. Passive noise control is not effective against low-frequency noise. Therefore, the purpose of this paper is to control the impact noise using active noise control. Since each impact noise is generated in a short period, LMS algorithm is difficult to use because of its slow convergence characteristics. On the other hand, frequency domain adaptive algorithm is known for fast convergence characteristics. In this paper, the effectiveness of active noise control using frequency domain adaptive algorithm is confirmed through simulations and experiments.. |
| 10. |
Xun WANG, Shinya KIJIMOTO, Yosuke KOBA and Koichi MATSUDA, Noise Barrier Using Feedback Active Noise Control, The 40th International Congress and Exposition on Noise Control Engineering (INTER-NOISE 2011), TS-6, SS33, 2011.09. |
| 11. |
Ikuma IKEDA, Shinya KIJIMOTO, Koichi MATSUDA, Yosuke KOBA and Keitaro KAGEYAMA, Active Noise Control Using Position of Evaluation Point, Journal of System Design and Dynamics, 4, 753, 1421--1427, Special Issue on D&D2008, Paper No. T2-08-0860, 2009.05. |
| 12. |
Ikuma IKEDA, Shinya KIJIMOTO, Koichi MATSUDA, Yosuke KOBA and Toshihiko HIGASHI, Active Noise Control Assuming Quiet Zone Movement, Journal of System Design and Dynamics, Vol.2，No.6，pp.1296-1305，2008, 2008.12. |
| 13. |
Ikuma IKEDA, Shinya KIJIMOTO, Koichi MATSUDA and Yosuke KOBA, Active Noise Control with a Moving Evaluation Point, Journal of System Design and Dynamics, Vol.2，No.1，pp.362-369，2008, 2008.03. |
| 14. |
Shinya Kijimoto, Yuichi SASAKI, Yoichi KANEMITSU, Koichi MATSUDA, Takashi YOSHIDA, Active Noise Control for Three-Dimensional Sound Field Using Fast Converging Algorithms, Journal of Environment and Engineering, vol.2, No.2, pp.257-265, 2007.03. |
| 15. |
Shinya KIJIMOTO, Hideo SUZUKI and Shun OGURO, Diffraction of Sound by Two Finite-Length Cascade Cylinders, The Journal of Acoustical Society of Japan(E), 19, 4, pp. 269- 273, 1998.01. |
