Integration of the efficiency of noise barrier caps in a 3D ray tracing method. Case of a T-shaped diffracting device

Road barrier diffracting caps have shown a renewed interest for several years since they give the opportunity of increasing the barrier efficiency without changing its overall height. First investigations on the efficiency of road barrier caps calculated with a boundary element method (BEM) have shown that the efficiency obtained with coherent line sources is underestimated compared to that with incoherent line sources, more representative of road traffic noise. The present work deals with the characterisation of the real performance of a T -shaped absorbing cap with road traffic noise conditions. Two different approaches are compared: on one hand calculations with the help of a BEM program able to achieve 2D and 2D and a half simulations are made; on the other hand outdoor measurements on a test-wall using a maximum length sequence technique are carried out. The goal in the two approaches is to isolate the top edge diffracted sound field in order to determine an extrinsic value of octave band efficiency of the cap for many source-receiver pairs. These results integrated in a ray tracing prediction method enable the integration of air absorption along each ray path and give the real efficiency of such a device in the case of complex and realistic configurations for barriers of finite length. (A)

[1]  Elden F. Ray,et al.  Applications of Attenuations and Reflections in ISO 9613-2, Acoustics – Attenuation of Sound During Propagation Outdoors – Part 2: General Method of Calculation , 2004 .

[2]  G. R. Watts.  ACOUSTIC PERFORMANCE OF NEW DESIGNS OF TRAFFIC NOISE BARRIERS , 1993 .

[3]  山本 貢平,et al.  inter-noise 97 , 1998 .

[4]  Louis F. Cohn.  HIGHWAY NOISE BARRIERS , 1981 .

[5]  E. N. Bazley,et al.  Acoustical properties of fibrous absorbent materials , 1970 .

[6]  Garai,et al.  European methodology for testing the airborne sound insulation characteristics of noise barriers in situ: experimental verification and comparison with laboratory data , 2000, The Journal of the Acoustical Society of America.

[7]  R. Volz,et al.  Improvement of sound barriers using headpieces with finite acoustic impedance , 1999 .

[8]  J. Defrance,et al.  A new analytical method for the calculation of outdoor noise propagation , 1999 .

[9]  M. Hasebe.  Sound reduction by a T-profile noise barrier. , 1995 .

[10]  P. Jean,et al.  THE IMPORTANCE OF SOURCE TYPE ON THE ASSESSMENT OF NOISE BARRIERS , 1999 .

[11]  S. Chandler-Wilde,et al.  EFFICIENCY OF SINGLE NOISE BARRIERS , 1991 .

[12]  D. N. May,et al.  The performance of sound absorptive, reflective, and T-profile noise barriers in Toronto , 1980 .

[13]  P. Jean.  A VARIATIONAL APPROACH FOR THE STUDY OF OUTDOOR SOUND PROPAGATION AND APPLICATION TO RAILWAY NOISE , 1998 .

[14]  Massimo Garai,et al.  Measurement of the sound-absorption coefficient in situ: The reflection method using periodic pseudo-random sequences of maximum length , 1993 .

[15]  Sabih I. Hayek,et al.  Mathematical modeling of absorbent highway noise barriers , 1990 .

[16]  H. W. Jones,et al.  Model studies of barrier performance in the presence of ground surfaces. Part II—Different shapes , 1984 .

[17]  D. Duhamel,et al.  SOUND PROPAGATION OVER NOISE BARRIERS WITH ABSORBING GROUND , 1998 .

[18]  D. Duhamel.  EFFICIENT CALCULATION OF THE THREE-DIMENSIONAL SOUND PRESSURE FIELD AROUND A NOISE BARRIER , 1996 .

[19]  Masaki Hasebe,et al.  A study on the sound reduction by T-profile noise barrier. , 1993 .

[20]  Simon N. Chandler-Wilde,et al.  THE PERFORMANCE OF T-PROFILE AND ASSOCIATED NOISE BARRIERS , 1991 .

[21]  Jorge P. Arenas,et al.  Modification of the Diffracted Sound Field by Some Noise Barrier Edge Designs , 2001 .

[22]  J. E. Piercy.  The draft international standard method (ISO/DIS 9613-2) for calculating the attenuation of sound during propagation outdoors , 1994 .

[23]  G R Watts.  ACOUSTIC PERFORMANCE OF TRAFFIC NOISE BARRIERS. A STATE OF THE ART REVIEW , 1992 .

[24]  D. N. May,et al.  Highway noise barriers: new shapes , 1980 .

[25]  J Tonndorf,et al.  Cochlear prostheses. A state-of-the-art review. , 1977, The Annals of otology, rhinology & laryngology. Supplement.

[26]  Simon N. Chandler-Wilde,et al.  Multiple-edge noise barriers , 1995 .

[27]  G. R. Watts.  Acoustic Performance of a Multiple Edge Noise Barrier Profile at Motorway Sites , 1996 .

[28]  Kyoji Fujiwara,et al.  EFFICIENCY OF A NOISE BARRIER ON THE GROUND WITH AN ACOUSTICALLY SOFT CYLINDRICAL EDGE , 1998 .

[29]  J. Beaumont,et al.  A new in situ method for the acoustic performance of road traffic noise reducing devices , 1998 .