1/17 Transmitted by the expert from the Netherlands Development of the SPERoN hybrid tyre/road noise model: Informal document No. GRB-48-7 (48th GRB, 1-3 September 2008, agenda item 8) Test track sections A short overview for GRB Sept 2008 Erik de Graaff, M+P consulting engineers
2/17 Optimisation of road surfaces, the history First phase (in the past): observation of the spread and selection of the most silent (top-top variation 5 db(a)) Second phase (current practice): optimisation by educated guess Example 1: single layer absorbing road surface was copied from airport runways (reduced splash and spray) Example 2: double layer absorbing road surface was optimisation of single layer both in absorption and in texture, but appeared to be too thick in its first trials (second optimisation necessary) Top-top variation 10 db(a) Third phase (in preparation): structured optimisation Well structured variation in test fields Computer programmes to optimise Fundamental knowledge Top top variation 15 db(a)?
3/17 SPERoN= Statistical Physical Explanation of Rolling Noise Computer model of tyre/road noise First goal Tyre: black box (the average tyre) Road surface: to be optimized Development by Chalmers university, M+P and Müller-BBM SPERoN v2.0 tyre response road texture load, speed contact model contact forces vibration related noise airflow related noise contributions statistical model sound energies multipole radiation model source strengths propagation model sound immission @ nearfield @ farfield
4/17 Data requirement for development Input to physical model: Surface properties; 2-1/2 D texture profile, acoustic impedance, mechanical impedance, flow resistance, micro-texture. Tyre properties: 3D tyre profile, tyre mobility, tread hardness, load and speed Input to statistical model: Spectral sound power levels of all tyre/road/speed combinations Input to propagation model: Source geometry, horn amplification, acoustic impedance, propagation geometry
5/17 44 different test sections where build on deserted road
6/17 Choice of test sections to allow maximal spread in relevant surface properties Frequency of absorption max [khz] 2 1.5 DAC / SMA ISO TSL 25-35 PAC 25 50 45-25 DPAC 65-25 Porosity [%] 25 10 3 TSL- DPAC 6-8 ISO 6 TSL 8 8 DAC 16 PAC 8-11-16 8 SMA 16SMA low Absorption high smooth Texture rough
7/17 Instrumentation for determination of surface properties
8/17 Measurement systems for determination of tyre properties Shown profile scanner for C1 tyres, also used scanner for C3 tyres Tyre mobility measured by Chalmers University
9/17 Rolling noise measurement system (shown far car (C1) tyres), similar system for truck (C3) tyres. 9 8 7 6 5 4 3 10 11 2 1 297.5 mm 147.5 mm 200 mm 1,11 2,10 3-9 100 mm
10/17 Sound absorption (extended surface method) (2) 90 mm 70 mm 50 mm
11/17 Air flow resistance log axis 100,000 10,000 Air Flow Resistance [R*s, Pa s/m] 1,000 100 10 1 19 20 21 22 23 2 3 4 5 6 7 8 9 15 24 31 10 11 12 13 14 16 25 26 27 28 29 30 17 18 ISO stone mastic asphalt DAC 0/16 thin porous asphalt layer porous asphalt concrete double layer porous asphalt concrete rubber DPAC
12/17 Surface texture
13/17 Micro Texture: skid resistance (British Pendulum Test)
14/17 Examples of near field rolling noise Effect of road surface texture on slicks and profiled tyres CPX spectra on SMA
15/17 Examples of near field rolling noise low texture fields, with varying acoustic absorption
16/17 Phase II additions (among others) Testing of Japanese Poro Elastic Rubber Surfaces (with support from Dr. Meierashi PWRI) Decoupling of texture, mechanical impedance and acoustic impedance by application of PERS surface with modifications: Sealed (no acoustic absorption) Standard (limited acoustic absorption) On porous layer (high acoustic absorption)
17/17 Results phase II surfaces Japanese Poro Elastic Road Surface shows high reduction potential 10 to 15 db over the entire frequency range compared to surface dressing 10 db at higher frequency range compared to ISO surface 95 90 CPX cars level [db] 85 80 75 70 65 ISO PERS1 SD 8/11 60 315 400 500 630 800 1000 1250 1600 2000 2500 3150 4000 5000 frequency [Hz]
18/17 Conclusions and outlook 44 Test sections represent wide variation in relevant acoustic surface properties (texture, absorption and mechanical impedance) Top-top differences in noise emission up to 15 db(a) Computer model is reliable and can be used to further optimize the noise emission of road surfaces Other parameters of elastic road surfaces have to be checked Rolling resistance Resistance to emergency braking Durability Etc Next goals for computer model Extend with Grip and Rolling Resistance Extend to optimize tyre/road combinations Further information can be found on www.silentroads.nl