AASHTO T 360:16(2020) Standard Method of Test for Measurement of Tire/Pavement Noise Using the On-Board Sound Intensity (OBSI) Method.
5.2. Using this method, measurements can be made to compare different pavements.
5.3. Complementing this test method are wayside methods including TP 98 for the determination of noise from isolated vehicle pass-by events, and TP 99 for the determination of continuous-flow traffic noise.
6. 1 . Selection of Test Section:
6.1.1. Pavement Surface—The test section shall have the same nominal material and surfacing for its length and width of the path to he tested. The test section shall he dry and free of debris to the extent practical.
6.1.2. Geometry and Grade—The test section should he a tangent (straight) section of the roadway. Horizontal curves should he avoided when possible, as should steep downgrades due to the potential for brake usage. Roadway geometry and approximate grade should he noted.
6.1.3. Wheel Path—Testing should he conducted with the test tire positioned in the normally trafficked wheel path. If testing is conducted outside of this path (for example, center of lane measurements), the location of the selected path shall be documented and reported.
6.1.4. Reflective Surfaces—There should be no acoustically reflective surfaces within 20 in. (0.5 rn) of’ the center of the wheel path along the length of the test section. If measurements must be made with an object(s) nearby, the location and nature of the object(s) should be documented.
6.2. Measurement Locations—Measurements shall be made alongside both the leading edge and trailing edge of the SRTT contact patch on the side of the vehicle opposite of the driver (see Annex A4 and Figure A4. 1). Figure A4. I includes the specified locations for the microphone probes during measurement.
6.3.1. Standard Test Speed—60 mph (97 kmlh) shall be uscd unless conditions do not permit, or the test purpose requires a different speed. If a speed other than the standard test speed of 60 mph (97 km/h) is used. the speed shall be clearly designated in the reporting of all sound intensity levels. Alternative standard test speeds shall be the highest achievable speed from one of the following: 45, 35, and 25 mph (72, 56. and 40 km/h, respectively). The length of the test section shall be that defined in Section 3.16. regardless of test speed. Corrections to sound levels as a function of test speed shall not be applied beyond the tolerance of the test speed. Data shall not be valid if brakes are applied during the measurement period.
6.3.2. Test Speed Variation—During the test, the vehicle shall travel with constant speed [±1 mph (±1.6 km/h)] over the test section in an appropriate gear setting.
Note 2—Use of cruise control is allowed to assist in maintaining constant vehicle speed.AASHTO T 360pdf download.