Unit of measurement

Noise level shall be measured in dB with A-weighting, expressed as dB (A).

Measuring apparatus

Driver-perceived noise level shall be measured by means of a sound-level meter as described in the first edition of publication 179/1965 of the International Electrotechnical Commission.

In the case of variable readings, the average of the maximum values must be taken.

the tractor must be unladen, i.e. without optional accessories, but must include coolant, lubricant; full fuel tank, tools and driver. The latter may not wear any abnormally thick clothing, scarf or hat. There may be no object on the tractor likely to distort the noise level;

the tyres must be inflated to the pressure recommended by the tractor manufacturer, the engine, transmission and drive axles must be at normal running temperature and, if the engine has cooling louvres, these must remain completely open;

if it is liable to affect the noise level, extra equipment powered by the engine or self-powered such as windscreen wipers, warm air fan or power take-off, for example, may not be in operation when measurements are being made; parts which normally operate at the same time as the engine, such as the engine cooling fan, for example, must be in operation when measurements are being made;

the test area must be in an open and sufficiently silent location: it may take the form, for instance, of an open space of 50-metre radius, having a central part with a radius of at least 20 m which is practically level, or of a level section having a solid track with as flat a surface and as few gullies as possible. The track must be as clean and dry as possible (e.g. free of gravel, leaves, snow, etc.). Slopes and irregularities are acceptable only if the variations in noise level caused by them lie within the error tolerances of the measuring equipment;

the surface of the track must be such as not to cause excessive tyre noise;

the weather must be fine and dry with little or no wind.

The driver-perceived ambient noise level due to the wind or other sources of noise must be at least 10 dB (A) below the noise level of the tractor;

if a vehicle is used for measurements, it must be towed or driven at sufficient distance from the tractor to avoid all interference. During measurements no object interfering with the measurements or reflective surfaces may he located within 20 m of each side of the test track and less than 20 m to the front or rear of the tractor. This condition can be considered fulfilled if the variations in noise level thus caused remain within the error tolerances; if not, the measurements must be discontinued for the duration of the intereference;

all measurements in a given series must be carried out on the same track.

The microphone must be located 250 mm to the side of the central plane of the seat, the side being that on which the higher noise level is encountered.

The microphone diaphragm must face forward and the centre of the microphone shall be 790 mm above and 150 mm forward of the seat reference point described in Annex III. Excessive vibration of the microphone must be avoided.