The battle is on to cut traffic noise

Press, 29 July 1976, Page 17

The battle is on to cut traffic noise

Most of us, at one time or another, have cringed as a revving motor-cvcle or a heavv truck has roared and pounded past. But ROD DEW reports that our ears might soon get a reprieve through new regulations coming into force . . .

Noise is the subtle enemy of modem civilisation. It can irritate, cause permanent loss of hearing, seriously affect health — often without the sufferer being fully aware of what is happening. And if field studies made recently in Britain and the United States, as well as in New Zealand, can be taken as a reliable guide, noise levels are increasing at an alarming rate. For many people, the most obvious and widespread noise pollution of the environment comes from motor vehicles. According to the Board of Health’s “Report on Noise,” the external radiated noise from individual vehicles or traffic streams is unlikely to cause hearing problems or physiological harm to the mass of the population. But in certain situations it can be harmful. It causes annoyance in the urban setting and frequently reaches levels which impair efficiency in tasks involving communication.

It is accepted that noise levels from traffic are increasing at the rate of 0.4 decibels a year and that noise pollution levels at the road side in New Zealand often exceed 80 decibels and, in some cases, 100 decibels.

The safe limit accepted for industry is 90 decibels. This growing problem is not unrecognised. Amendments to the Transport Act 1962 are planned to control noise emission from vehicles and might become law during the present session of Parliament.

Possibly in anticipation of this, the Ministry of Transport had planned to appoint three noise control officers for New Zealand to lead the assault on noise pollution. Unfortunately, this proposal became one of the victims of re cent economy measures

within the ministry. However, a member of the automotive engineering section in Wellington

has a watching brief on noise, and a single noise control officer has been appointed — Mr R. W. Wright, who is based in Christchurch.

A thoughtful person with a keen interest in the environment, Mr Wright has been busy in the six months he has held his position, making an extensive study of methods being developed overseas to combat noise pollution. He has taken many measurements for his own information and has worked on a research project at the University of Canterbury.

At the same time he has been available to investigate complaints. “There have not been a great number of direct complaints,” he says.

“Most of them are of a general nature and these are very hard to pursue.” But Mr Wright’s official position is not yet widely known and he is likely to be much more in demand in future. At present, he has no enforcement power. In most cases so far he has been able to discuss problems with the parties concerned and a reasonable solution has been found.

He suggests that persons who have a complaint, such as about heavy trucks rumbling past their properties, should first speak to the operator. “In my experience a responsible firm will show concern. I am only one man — there is a limit to how much I can do.”

Under existing regulations, only a traffic officer or a vehicle inspector has the power to order a vehicle off the road if its condition causes unreasonable noise. Tiie advent of the internationally - accepted sound-level meter has strengthened their position in this regard. It is the most vital part of Mr Wright’s equipment. It measures noises ranging from 30 to 140 decibels and gives readings in what is known, technically, as dbA. The instrument has been weigh-

ted electronically so that it takes into account the sensitivity of the human ear to the noise being measured. In other words, the meter is less sensitive to low frequencies. “No-one claims it to be perfect,” says Mr Wright. “But for practical purposes, on the job, the dbA measurement has become internationally accepted.” The test which Mr Wright does on vehicles is that recommended by the International Standards Organisation and is known as the “pass by test.” A vehicle is accelerated at. maximum power in a middle gear from 50km/h over a strip 20 metres long. The reading is taken with the microphone 7.5 metres from the vehicle track. It is repeated with the vehicle travelling in the opposite direction and the average computed.

A drawback is that it needs to be done in an area where there is little out; side interference — such as on the causeway near Sumner. But it is possible that in the future such a test will be demanded by traffic officers who are concerned about the noise emission of any vehicle. The new regulations which are expected to be approved by Parliament shortly are likely to establish maximum noise levels for all classes of new vehicles. They will have to conform to this level before being allowed on the road and will then be expected to maintain a slightly less stringent “in use” level.

The maximum noise levels suggested by the Board of Health report are expected to provide the basis for the proposed law. Initially, these will not be difficult to conform to but they are likely to be tightened up at a later stage.

The suggested maximum noise levels for new vehicles, with the recommended maximum “in use” level in parentheses, are:—

Power-cycle up to 50 cu. cm, 77dbA (80dbA). Motor-cycle 51 to 125 cu. cm, 82 (85).

Motor-cycle over 125 cu. cm, 86 (89). Cars and derivatives, 84 (87).

Vehicles more than 2 Mg tare weight with gross power less than 150 kw, 89 (92). Vehicles of more than 2mg tare weight with gross power of 150 kw or more, 92 (95). Random samples will probably be taken of each new model imported and given the "pass by test.” Development work is also proceeding on a substitute method for measuring noise at the exhaust for roadside enforcement. This, of course, has the disadvantage of not measuring tyre and body noises.

With the “pass by test,” all noise involved with the vehicle —even wind noise — is taken into account. A couple of empty tins rolling around in the boot might result in an unfavourable reading. Eventually, it is expected that all vehicles, irrespective of age, will have to comply with noise regulations. Although most road traffic is cars, Mr Wright believes that noise from trucks and motor-cycles is the most irritating. “In some instances, better maintenance and better driving or riding habits — particularly in the case of motor-cyclists — would overcome this problem. Motor-cycles with a powerful sound, it would appear, are in some cases considered to have enhanced sales potential. They could be silenced much more effectively without great loss of power.”

A considerable amcunt of work has been done on truck noise levels in the United States and Britain and it is expected that trucks imported in future will be much quieter because of this investigation. Nevertheless, the responsibility for reducing traffic noise is not that of the vehicle manufacturers, alone. Traffic control, area planning, highway development, the interaction of tyres with road surfaces, all have a bearing on

noise. Faulty planning decisions by local authorities have aggravated the situation by allowing residential development on major traffic routes. Existing roads are being widened, thereby bringing vehicle noise closer to existing development. And so on . . .

Noise is one of the major problems of our time. It is a complicated subject because the danger from it is in relation to exposure time. And it is not only the innocent bystander who suffers. It is a scientific fact that noise levels inside some vehicles are so great that exposure to them for sustained periods can result in a serious impairment of hearing. In the last 20 years in New Zealand, vehicle numbers have increased by 185 per cent while the population growth has been 47 per cent. In terms of exposure to transport generated noise, the environment is deteriorating. The harnessing of the ordinary motorist with further regulations must be regretted. But it is obvious that the present noise trend cannot be allowed to continue.