The Single Event Level SEL Angelo Farina Dip

The Single Event Level SEL Angelo Farina Dip. di Ingegneria Industriale - Università di Parma Parco Area delle Scienze 181/A, 43100 Parma – Italy angelo. farina@unipr. it 30/11/2012 Single Event Level - SEL 1

The Equivalent Continuous Level (Leq): The continuous equivalent level Leq (d. B) is defined as: where T is the total measurement time, p(t) is the instantaneous pressure value and prif is the reference pressure 30/11/2012 • Leq, T d. B (linear frequency weighting) • LAeq, T d. B(A) (“A” weighting) Single Event Level - SEL 2

Definition of SEL (Single Event Level) the SEL is the equivalent level packed in one second 30/11/2012 Single Event Level - SEL 3

Definition of SEL (Single Event Level) the SEL is the equivalent level packed in one second SEL 30/11/2012 1 s Single Event Level - SEL 4

Example of SEL (Single Event Level) Time history of the passage of an aircraft 30/11/2012 Single Event Level - SEL 5

Noise from roads and railways Angelo Farina Dip. di Ingegneria Industriale - Università di Parma Parco Area delle Scienze 181/A, 43100 Parma – Italy angelo. farina@unipr. it 30/11/2012 Single Event Level - SEL 6

Contnuous Line Sources Many noise sources found outdoors can be considered line sources: roads, railways, airtracks, etc. Geometry for propagation from a line source to a receiver - in this case the total power is dispersed over a cylindrical surface: In which Lw’ is the sound power level per meter of line source 30/11/2012 Single Event Level - SEL 7

Coherent cylindrical field • The power is dispersed over an infinitely long, pulsating cylinder: L r In which Lw’ is the sound power level per meter of line source 30/11/2012 Single Event Level - SEL 8

“discrete” (and incoherent) linear sources Another common case is when a number of point sources are located along a line, each emitting sound mutually incoherent with the others: Geometry of propagation for a discrete line source and a receiver - We could compute the SPL at the receiver as the energetic (incoherent) summation of many spherical wavefronts. But at the end the result shows that SPL decays with the same cylindrical law as with a coherent source: Lw’ Note that the incoherent SPL is 2 d. B louder than the coherent one! 30/11/2012 Single Event Level - SEL 9

A road is a sequence of point sources d V (km/h) EXAMPLE: • V = 50 km/h • Q = 500 vehicles/h • Lw, 1 veic = 90 d. B(A) Hence: • d = V/Q = 50000/500 = 100 m • Lw’ = Lw, 1 vehicle – 10·log 10(d) = 90 – 10·log 10(100) = 70 d. B(A) Consequently, at a distance r = 50 m, we get: • Lp, 50 m = Lw’ – 10·log 10(r) – 6 = 70 – 10·log 10(50) – 6 = 47 d. B(A) 30/11/2012 Single Event Level - SEL 10

Definition of SEL (Single Event Level) The SEL is the equivalent level packed in one second SEL Leq 30/11/2012 Single Event Level - SEL 11

Relationship between SEL and Lw’ We did find that: SEL is measured at the standard distance r = 7. 5 m, and referes to just one of the Q vehicles passing each hour, packed in one second: When V=50 km/h, we get: SEL = Lw – 26. 19 d. B(A) 30/11/2012 For a constant value of Lw, SEL decreases with the speed of vehicles V Single Event Level - SEL 12

Computing the time profile 30/11/2012 Single Event Level - SEL 13

Effect of vehicle’s speed Sound Power Level Lw increases with speed above 30 km/h 30/11/2012 Single Event Level - SEL 14

Effect of vehicle’s speed 6 d. B / ra dd. Aerodynamics Rolling Engine Sound Power Level Lw increases with speed above 30 km/h 30/11/2012 Single Event Level - SEL 15

Time profile vs vehicle’s speed Increasing the speed the profile becomes shorter and higher 30/11/2012 Single Event Level - SEL 16

SEL vs vehicle’ speed -3 d. B /ra dd . d. d a r B/ 3 d SEL has a minimum around 70 km/h 30/11/2012 Single Event Level - SEL 17

SEL vs vehicle’ speed SEL has a minimum around 70 km/h 30/11/2012 Single Event Level - SEL 18

Definition of personal exposure level (Lep): Lep The personal exposure level Lep (d. B) is defined as: where 8 h is the standardised duration of a work day. Hence: 30/11/2012 Single Event Level - SEL 8 h 19

Example of Lep computation: 75 1 h 30/11/2012 80 1 h 84 75 2 h 75 3 h Single Event Level - SEL 1 h 78 2 h 20