CARL BRO MEASURES NOISE	06/12/2005
	Noise is an increasing annoyance for people living near roads with high traffic density. Removal of the traffic can only be done at very high costs. However, it is possible to remove much noise by laying out a new pavement on the road. Carl Bro can now measure the effects of low-noise pavements. Depending on the driving speed, approximately three thirds of the noise from a passing car comes from the tires. When air is pressed through the narrow channels and is squished between rubber and stones in the pavement, this produces a noise emission. A softer and more open pavement will allow the air to slip out. This is why asphalt companies offer pavements, which reduce the noise – the so-called low-noise pavements. These pavements have become more and more common and are often applied in areas where people are living very close to roads. »It can be very difficult to decide, whether the solution should be a new asphalt pavement or other measures such as anti-noise baffles or the like. Carl Bro Pavement Consultants can easily and rapidly measure the noise level generated by the present pavement, resulting in a far better basis for any decisions. After any remedial measures it is possible to have accurate documentation as to how much the noise was reduced, « explains project manager Troels Kragh, Carl Bro Group. Soundproof trailer The measurements are so-called CPX measurements carried out according to an ISO standard. Tires with very special capabilities are mounted in a closed soundproof trailer, where microphones record the sound without any disturbing external elements. The data are treated and the result is a so-called CPX noise level for a passenger car tire and a truck tire. »Normally, noise measuring is very difficult. In order to obtain the so-called SPB value (Statistical Pass By), more than a hundred cars must be measured in each measuring location. However, measuring the CPX noise level allows calculation of a SPB value on the basis of known reference measurements. This is far easier and less expensive,« Troels Kragh points out. In spite of the fact that this method is a rather new one, many road agencies have already had CPX measurements made by Carl Bro. Asphalt companies are also among the customers. They are applying the method in their low-noise pavement development work. Call Troels Kragh on +45 2723 1466 or mail him on ttk@carlbro.dk