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(1) Snowmobile sound pressure levels shall be in accordance with 23-2-634 , MCA.

(2) Sound pressure levels in decibels shall be measured on "A" scale of a sound level meter having characteristics defined by current American National Standards Association Sl, 4-1966 "general purpose sound meter." Measurements shall be made in accordance with applicable practices outlined in "Exterior Sound Levels for Snowmobiles -SAE J192" or the procedure set forth in exhibit "A" attached hereto and hereby made a part hereof.

(3) Manufacturer's certification required by 23-2-634 , MCA, shall be evidenced by a label permanently affixed to the exterior portion of the snowmobile chassis. The label shall be in the following form: "This vehicle was manufactured by (name of company), (address of company), and conforms to all applicable federal and state requirements in effect on the date of its manufacture VIN # , date manufactured .

(4) Exhibit "A" is entitled "Procedures for the Field Measurement of Snowmobile Noise Pursuant to 23-2-634 , MCA".

(a) A site suitable for making noise measurements for purposes of enforcing these regulations shall consist of a flat open space free of large reflecting surfaces such as signboards, buildings, or hillsides located within 50 feet of either the vehicle or the microphone.

(b) The surface of the ground within the measurement area shall be covered with snow.

(c) The ambient sound level (including wind effects) due to sources other than the vehicle being measured shall be at least ten dbA lower than the level of the tested vehicle.

(d) The sound level meter shall be set for "fast" response and for the "A" scale network. If the meter is equipped with "hold" it may be used. ("Impulse" may not be used.)

(e) The meter shall be observed while the vehicle is accelerating. The applicable reading shall be the highest sound level obtained for the run, ignoring unrelated peaks due to extraneous ambient noises.

(f) The meter shall be calibrated daily, using either internal or external calibration techniques as specified by instrument instructions.

(g) Instrument manufacturer's specifications for orientation of the microphone relative to the source of sound and the location of the observer relative to the meter should be adhered to.

(h) It is recommended that measurements be made only when wind velocity is below 12 mph.

(i) An additional five dbA allowance over the sound level limit is recommended to provide for variations in measurement site, vehicle operation temperature, humidity, and wind velocity.

(j) Technically trained personnel should be consulted in the selection of equipment and all measurements shall be conducted only by qualified persons trained in the current techniques of sound measurement.

History: Sec. 23-2-641 MCA; IMP, Sec. 23-2-634 MCA; Eff. 12/31/72; AMD, 10/5/73; AMD, Eff. 8/5/74.

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