Visualization Techniques to Identify and Quantify Sources and Paths of Exterior Noise Radiated from Stationary and Nonstationary Vehicles

Transcription

1 Purdue University Purdue e-pubs Publications of the ay W. Herrick Laboratories School of Mechanical Engineering 6-2 Visualization Techniques to Identify and Quantify Sources and Paths of Exterior Noise adiated fro Stationary and Nonstationary Vehicles Hiroshi Stuart Takata Purdue University, Follow this and additional works at: Takata, Hiroshi Stuart, "Visualization Techniques to Identify and Quantify Sources and Paths of Exterior Noise adiated fro Stationary and Nonstationary Vehicles" (2). Publications of the ay W. Herrick Laboratories. Paper This docuent has been ade available through Purdue e-pubs, a service of the Purdue University Libraries. Please contact epubs@purdue.edu for additional inforation.

2 Visualization techniques to identify and quantify sources and paths of exterior noise radiated fro stationary and nonstationary vehicles Hiroshi Takata, Takuo Nishi Isuzu Motors Ltd. Hyungseok Kook Kookin University Gregory Moebs Caterpillar Inc. Patricia Davies and J. Stuart Bolton Purdue University

3 Visualization Technique of Stationary Vehicles Location of hidden sources. Source ranking of hidden sources. Transission path of hidden sources. Contribution of hidden sources. Currently no ethod exist which can provide these inforation easily.

4 Location of Hidden Sources MISO syste u u2 u K g g2 gn g2 g22 g2n gk gk2 gkn Selection procedures which have been developed to-date are of two kinds: Exhaustive search by using SVD Sequential search by using Partial coherence analysis However these procedures can not be used to localize sources. x x2 xn hy h2y hny Two new kind of algorith is developed. Partial SVD ethod (PSVD). + y

5 Partial SVD ethod (PSVD) eove one signal fro the other signals by using a partial coherence procedure. The singular values of the conditioned cross spectral atrix are less than or equal to those of original atrix. ; 2 2 ; ; n- n-. The ore significant the signal that is reoved, the ore the singular values of the conditioned cross spectral atrix will be reduced.

6 Experiental Setup 6 input icrophones output icrophone 3 incoherent sources (loudspeakers) u 3 u u 2 s 3 s s 2 x 6 x 3 x x 4 x 2 x 5 y

7 Experiental esults The singular values of cross spectral atrices of: (a) All 6 transducers (b) Transducer group (x, x2, x3) Singular Values 4 5 Singular Values Frequency (Hz) Frequency (Hz) (c) Transducer group (x, x2, x6) (d) Transducer group (x2, x4, x5) Singular Values 4 5 Singular Values Frequency (Hz) Frequency (Hz)

8 Integrated Nearfield Acoustical Holography (INAH) Source ranking of hidden sources Transission path of hidden sources Contribution of hidden sources By using NAH and partial field decoposition

9 Decoposition of the Sound Field The partial field deterination proble has been approached in two ways: Partial coherence analysis Singular value decoposition Experiental Setup

10 esults: Partial field Partial coherence SVD procedure

11 esults: Partial field 2 Partial coherence SVD procedure

12 esults: Partial field 3 Partial coherence SVD procedure

13 Exterior Noise Field of a Vehicle - Experiental Setup Twelve candidate icrophones. Sound pressures were easured on a plane 5c away fro the left side panel on a 48 x 9 grid, with a inter-icrophone spacing of 5c, by using a 4 x 9 planar icrophone array. Idle (stationary).

14 esults: Localize sources Singular values of input signal cross spectral atrix based on: (a) All 2 icrophones (b) Microphone group (2, ) Singular Values 2 Singular Values Frequency(Hz) Frequency (Hz) (c) Microphone group (2,, 8) (d) Microphone group (2,, 8, 9) Singular Values Singular Values Frequency (Hz) Frequency (Hz)

15 esults: Transission path Partial sound field associated with reference Partial sound field associated with reference 2

16 esults: anking, Contribution Two utually incoherent sources at 37 Hz: Source location and ranking by integrating AI over the hologra plane. Engine head (77 % of total sound power) 2. Oil pan (23 % of total sound power) Source contribution at the center point fro the side panel by reconstruction of AI at the observation point. Engine head (95 %) 2. Oil pan (5 %)

17 Visualization Techniques of Nonstationary Vehicles Standard Vehicle Passby Tests De-Dopplerization (propagation distance calculation) backward propagation procedure forward propagation procedure Aplitude Correction (copensating for spherical spreading) intuitive ethod axiu likelihood estiation Array Design Experiental esults

18 Kineatics of Moving Noise Sources Source signals : eceived signals : [ ( )] ( ) [ ] [ ( )] = x x t + y y t + z z t s e s e s e p s y ( t) = Aexp ( jωt) ( A t ) = j t exp ω c M Delay-and-su beaforer : zt () w y ( t ) = = c(t-t e ) (Mach nuber effects on aplitude neglected) = / c O(x,y,z,t) = (for constant velocity V) M( x Vt) + ( x Vt) + ( M )( y + z ) M 2 y x Source θ x s = V t e x s = V t V(t-t e )= V/c (x - V t) cos θ = x - Vt + M

19 Beaforing on a econstruction Plane Attached to and Moving with the Vehicle y reconstruction plane oving with vehicle z x y s stationary icrophone array x s

20 Backward Propagation p(t) t r (a) p(t) t r =t e +D(t e )/c (b) p(t) t e (c) (a) Calculate the propagation distance, (t r ), for the saples received at t r (receiver tie) (b) Generate the eission tie vector corresponding to the receiver ties t e = t r -(t r )/c (c) The resulting non-equi-spaced tie history is resapled to obtain an equally-spaced tie history in the source (i.e., eission) tie frae

21 Forward Propagation p(t) t r (a) p(t) t e =t r (t r )/c (b) p(t) t e (c) (a) Calculate the instantaneous distance, D(t e ), between the assued source position and the icrophone for an assued signal eitted at t e (b) Generate the corresponding receiver tie vector by using the forula, t r = t e +D(t e )/c (c) The easured icrophone outputs sapled at equally-spaced saple ties in the receiver tie frae are resapled using the unevenly-spaced receiver tie vector obtained in (b)

22 Forward vs. Backward Calculations siulated results for 35 k/h cruise test. denotes siulated loudspeaker location; loudspeaker at 295 Hz, front hub at x = -.24, 5 Hz analysis bandwidth. results fro backward propagation procedure results fro forward propagation procedure The calculation tie was reduced by a factor of three by using the forward propagation procedure when copared to the backward propagation procedure.

23 Aplitude Estiation Aplitude Estiation = c t j A t y exp ) ( ω ( ) = ) ( M t y w t z = + = exp M c c t j A w ω ( ) t j A ω exp = = M w = ( with and ) Spherical spreading in near field Weighting factor /M (intuitive weighting factor)

24 Maxiu Likelihood Estiation assuptions : source wavefor unknown, source position known source signals : a(t) tie shifted easured signals : in vector for : noise : y n () t y = a(t) s + n c c + ( ) t + c = a t + n t + c where y = { ( t + c) y ( t + c) y ( t c) } T y,,..., M + M s =,,..., M T n = { n } T n,,..., n M

25 Maxiu Likelihood Estiation (cont.) p y a( t) denotes the joint probability density function of the vector y being observed when the signal source aplitude was a(t) at tie t ln p = ln det 2 [ 2πK ] [ y as] K [ y a ] y a( t ) n n s 2 where K n noise covariance atrix Then s K s K - n aˆ ML = - n â ML s y = s s y s M y = aˆ ML() t = M axiizes the pdf ( t + c) = 2 p y a( t) (for spatially white background noise) w = M = 2 new weighting factor

26 esults (D-siulation, intersensor space 5 c) (a) (b) 5 5 elative Power (db) 5 elative Power (db) x () 6-icrophone array (f = 5 Hz, x = ) x () 64-icrophone array (f = 5 Hz, x = ) w w = = M = M 2 Sidelobe levels decreased by ore than 5dB as either the nuber of icrophone or array aperture size is increased.

27 Array Design z().2.8 y j,rss / N r z () x () x() positions of icrophones 4 2 x () 2 4 z () array pattern at 2 Hz ando array was randoly generated and snapped to an underlying grid. ando array reduces the nuber of redundancies in the co-array.

28 Experiental Setup On-board vehicle: to HP: ch. 8 Photocell Transducer AC Inverter 2 V Car Battery Signal Generator FM Transitter Power Ap Loudspeaker adar eceiver adar Eitter to HP: ch. 9 Mic Mic 2 Mic 6 ibbon Connector Signal Conditioner Patch Panel FM eceiver Coputer PC-IB HP Model 3565 fro: photocell fro: radar

29 Experiental esults Source localization results for 5 k/h cruise test, loudspeaker at 5 Hz, x =.29, 5 Hz band AP2_5

30 Experiental esults (cont.) Visualization results for acceleration test, loudspeaker at 85 Hz, x = 2.34

31 Conclusions The partial SVD ethod associates the reference signals ore directly with the physical sources than does the partial SVD ethod. The partial coherence technique is applicable to the decoposition of the sound field fro hidden sources. Noise source visualization successful for nonconstant velocity (capable of resolving loudspeaker and tire noise). Iproved coputation tie by using forward propagation procedure. educed sidelobe levels by using axiu likelihood estiation for aplitude of the source strength.