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SAE J1169-2007: Measuring Light Vehicle Exhaust Sound Levels Under Stationary Conditions (Cancelled)
SAE J1169-2007 was a surface vehicle standard that established a test procedure, environment, and instrumentation for measuring the exhaust sound level of passenger cars, multipurpose vehicles, and light trucks under stationary conditions. Originally issued in 1977 and revised several times, it was officially cancelled in July 2007 due to technological advances that rendered its test conditions impractical. The standard has been superseded by SAE J1492, which provides a more modern approach using continuous measurements over a range of engine speeds.
🛠️ Overview and Scope
The standard was designed as a guide for governmental agencies to enforce in-service sound level regulations for light vehicles. It focused specifically on exhaust noise, not maximum vehicle sound levels. The procedure required steady-state measurements at 3/4 of the maximum rated engine speed (MRES) with the transmission in neutral or park and the engine at normal operating temperature. Accessories like air conditioning were turned off, and the hood was closed.
Key instrumentation included a Type 1 sound level meter set to slow exponential time-averaging and A-weighting, along with an acoustic calibrator meeting ANSI S1.4 and S1.40 requirements. Engine speed had to be measured with an accuracy of ±2% or better.
Test Environment and Microphone Positioning
The test site had to be an outdoor hard surface free from large reflecting surfaces within a 3 m radius. Ambient sound levels needed to be at least 10 dB below the test vehicle’s sound level. The microphone was positioned 0.5 m from the exhaust outlet reference point at a 45° angle (±0°, –10°) to the flow axis, at a height not less than 0.2 m from the ground. For under-vehicle outlets, special positioning rules applied to avoid interference.
The following table summarizes the key test parameters:
| Parameter | Requirement |
|---|---|
| Engine speed | 3/4 of maximum rated engine speed (MRES), held constant |
| Sound level meter | Type 1 per ANSI S1.4; slow exponential time-averaging; A-weighting |
| Microphone distance | 0.5 m from exhaust outlet reference point |
| Microphone angle | 45° (+0, –10°) to flow axis |
| Test site surface | Hard, reflective (concrete, asphalt) |
| Ambient noise | At least 10 dB below measured level |
| Measurement repetition | Two readings within 2 dB; average reported |
⚠️ Why Was SAE J1169 Cancelled?
The standard’s reliance on 3/4 MRES became a major limitation. As noted in the rationale section of the standard, many modern engines cannot reach 3/4 MRES in neutral because of fuel cut‑off software designed to prevent over‑revving. This made it impossible to conduct the test as specified. Additionally, the slow exponential time‑averaging characteristic (slow meter response) was considered outdated compared to the fast response used in newer standards.
Common Pitfall: Attempting to apply SAE J1169 to vehicles with electronic engine management often results in unstable engine operation or triggering of fuel cut‑off. Engineers must recognize that the procedure is no longer valid for modern light vehicles.
SAE J1169 was superseded by SAE J1492, which takes a continuous measurement over a range of engine speeds and uses fast time‑averaging. This modern approach better captures the exhaust sound characteristics and is compatible with today’s engine control systems.
Design Insight: The cancellation of J1169 highlights how standards must evolve with technology. The shift from a single‑speed steady‑state test to a continuous sweep reflects both advances in measurement capability and the need to adapt to modern engine management strategies.
Frequently Asked Questions
Q: What engine speed did SAE J1169 require?
A: The test was performed at 3/4 of the maximum rated engine speed (MRES) as specified by the vehicle manufacturer, held constant during measurement.
Q: Why was the standard cancelled?
A: It was cancelled in July 2007 because many modern engines cannot reach 3/4 MRES in neutral due to fuel cut‑off software, and the slow exponential time‑averaging metric was outdated. It was replaced by SAE J1492.
Q: What instrumentation was specified?
A: A Type 1 sound level meter per ANSI S1.4 with slow time‑averaging and A‑weighting, an acoustic calibrator per ANSI S1.40, and an engine speed measurement device accurate to ±2%.
Q: How does SAE J1492 differ from J1169?
A: SAE J1492 measures exhaust sound continuously over a range of engine speeds using fast exponential time‑averaging, rather than a single speed with slow averaging.
