Shimon,
The results are not surprising and have been observed elsewhere.
SMA has a rough surface-texture that prevents air entrapment between tyre
and pavement and therefore reduces noise generated. Reductions between 1
and 10 dBA are feasible.
Max Lay
----- Original Message -----
From: שמעון נסיכי
To: [log in to unmask]
Sent: Monday, December 27, 2004 7:03 PM
Subject: Acoustic Anomaly (?) of Asphalt Mixtures
Dear Friends,
I would like to have your comments on the following issue:
Acoustic Anomaly (?) of Asphalt Mixtures
We have recently constructed test sections of several types of asphalt
mixtures as follows:
Dense Asphalt Mix (reference) – 5.5 % air voids
Porous Asphalt Mix - 20 % air voids (GEOMETRIC MEASUREMENT)
SMA – 8% air voids
Acoustic measurements were conducted following construction and before the
road have been opened to traffic, in accordance with ISO 11819-1. These
measurements have revealed the following results):
MEAN DIFFERENCES- ACOUSTIC MEASUREMENTS
(note – ΔLis the reduction in noise compared with the
reference mix - the dense graded asphalt)
VEHICLE
TYPESPEED
Km/rΔLMAXΔLEQ
SMA 0/8POROUS
ASPHALTSMA 0/8POROUS
ASPHALT
PRIVATE
CAR50
3.83.95.63.7
80
4.33.35.85.1
100
4.54.78.26.6
TRUCK50
3.02.76.76.3
80
--4.14.1
These measurements demonstrate the superiority of the SMA vs. the POROUS
MIX in terms of acoustic performance – an anomaly contradictory to common
engineering belief.
In this respect I have the following questions:
Have you ever encountered similar phenomena?
Could the acoustic performance be reversed (i.e. the [Porous Asphalt will
outperform the SMA ) after the road will be opened to traffic?
Thanks for your answer
Shimon Nesichi, M.Sc.,
Managing Director,
Materials and Research Division,
Public Works Department,
Ben Zvi Rd. 55, POB 49057
Tel Aviv, 61940
Israel
