Washington Administrative Code
Title 173 - Ecology, Department of (See also Titles 197, 317, 372, and 508)
Chapter 173-58 - Sound level measurement procedures
Section 173-58-080 - Close proximity exhaust system sound level measurement procedure
Current through Register Vol. 24-06, March 15, 2024
This section establishes specific procedures for the measurement of sound levels from exhaust systems at a distance of 20 inches (0.5 meter) from the exhaust outlet. The procedures of subsections (3), (4) and (5) of this section shall not be used for exhaust systems which utilize the introduction of water to the exhaust gas flow for the purpose of muffling the exhaust noise levels, or systems which exhaust the gas flow directly into water.
(1) For the purposes of this section "vehicle" means any motor driven contrivance used as a means of transportation or recreation off of public highways.
(2) Initial inspection. An initial inspection of the vehicle exhaust system shall be conducted to determine if the following defects or modifications exist:
If the above defects are observed and are a violation of the muffler integrity standards established for the type of vehicle which is being inspected, then a citation shall be issued in accordance with the enforcement section of the applicable regulation.
An evaluation of the vehicle sound level shall also be made by the enforcement officer, using the human ear as a sensing device.
If the exhaust noise is discernibly louder than the engine noise, or if any of the defects or modifications described above exist but are not violations of applicable regulations, the enforcement officer shall request the vehicle operator to submit the vehicle to any measurement procedures described in this chapter which are applicable to the type of vehicle being inspected. If the operator refuses to submit the vehicle to these measurement procedures, he shall be in violation of this chapter.
(3) Test site and instrumentation set up. The test site and instrumentation shall be set up as follows:
For vehicles provided with exhaust outlets spaced more than 12 inches (0.3 meter) apart, measurements shall be made for each outlet as if it were the only one, and the highest level shall be recorded. If the exhaust outlets are less than twelve inches (0.3 meter) apart, a single measurement shall be made for any one of the outlets.
For vehicles with a vertical exhaust, the microphone shall be placed at a height of 48 +- 2 inches (1.2 meter). Its axis shall be vertical and oriented upwards. It shall be placed at a distance of 20 +- 1 inches (0.5 meter) from the side of the vehicle nearest the exhaust outlet.
For vehicles with the exhaust system outlet near the engine, the engine hood (if one exists) should be closed as much as possible to reduce engine noise.
If a measuring device is attached to the exhaust outlet and the microphone to maintain proper distance, insure that no vibrations from the vehicle shall be transmitted to the instrument.
(4) Vehicle operation. The vehicle shall be operated as follows:
(5) Measurement. The exhaust system sound level shall be measured as follows:
Statutory Authority: Chapter 70.107 RCW. 79-04-033 (Order DE 78-19), § 173-58-080, filed 3/22/79.