Measurement of Exhaust Sound Levels of Stationary Snowmobiles
This SAE Recommended Practice establishes the test procedure, environment and instrumentation for determining the sound levels of snowmobiles in the stationary test mode. This test method is intended to provide an accurate measurement of exhaust and other engine noise and may be used to evaluate new and in-use snowmobiles to determine compliance with noise control regulations. Sound level measurements obtained with this test method are not intended as an engineering determination of overall machine noise. For this purpose, the use of SAE J192 is recommended.
This revision is proposed to address issues observed while conducting sound pressure level measurements using the current document. Those issues were reported to committee members by users of this document. In fact, snowmobile transmission calibrations have evolved over the years and because of different torque characteristics of newer engine designs, the snowmobile transmissions of a large number of models are fully engaged at 4000 rpm. This situation leads to the impossibility of conducting the test at 4000 rpm on those models without damaging the vehicle transmission component, especially the drive belt and drive pulley that are part of the CVT system. Tests were conducted by members of the committee and a new operating engine speed of 2500 rpm is proposed in this revision.
Some modifications are also proposed to the measurement section. Those modification are there for added clarity and are not intended to modify the measurement procedure.
A minimum SPL limit is also included in this revision. The limit used to enforce noise levels by snowmobile trail officers was 88 dB when performing the test at 4000 rpm. Tests conducted when decreasing operating engine speed from 4000 rpm to 2500 rpm showed an SPL decreasing by 5.3 dB on average. The SPL limit that is added to this document is 82 dB and was measured on very hard pack snow conditions typical of a snow covered parking lot in the winter. Therefore the ground condition section is also modifed to account for this ground condition. A similar SAE document (SAE J2825) includes minimum sound limits.