Originally Posted By: Max_Wander
Sure, while at it I can park my car on a soundstage before and after the oil change and pay the audio engineer $200/hr to do a 3D spectrum analysis on the resultant waveforms taken from various angles by expensive microphones...
I was thinking of something with a little precision. Like an electrical engineer taking readings through transducers bolted to various points on the engine block where they can't be affected by ambient sound.
Originally Posted By: Max_Wander
but apparently that's not nessecary given that people are noticing the sounds due to the existence of the different sounds themselves. Some people are quite perceptive and know their cars as demarpaint said, enough not to confuse it with a compressor cycing or injectors ticking.
I'm not assuming anyone here would be so naive as to confuse injectors ticking or a compressor cycling with engine noise. I'm saying that the human ear is at best uncalibrated and incapable of making a quantitative measurement, even when the noise is perfectly identifiable. I say this as an engineer who has worked in acoustics for 22 years. An engine produces a *symphony* of sounds all the time, and the relative intensities of the various sound components change radically with temperature, engine load, atmospheric conditions, and yes, even oil. Occasionally one sound will rise to preceptibility above the other sounds, that doesn't mean that the sound "didn't exist" before, it just means it was buried under other sounds. For example- EVERY engine has detectable (to instruments) piston slap, all the time every time its running. But we only notice it when it dominates over other sounds. such as a cold engine with short piston skirts. Every engine has wrist-pin noise... all the time. Every engine has valvetrain noise.... all the time. You can even hear some component of the actual combustion process, but you can't identify it except when it becomes detonation. Only under certain conditions does a sound stand out as being different, and its REALLY hard to correlate the change with the cause. To reduce an effect down to whether or not the oil caused it, you really need to be able to prove that the noise is there CONSISTENTLY with one oil versus the other. Sometimes you can do that, I don't disagree. But it really doesn't prove anything about wear anyway.
