Greg Lake - Still You Turn Me On

"RamblinRover Luxury-Yacht" (ramblininexile) 10/17/2016 at 18:32 • Filed to: musiclopnik

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It’s been alleged that “pretentious” is spelled “ELP”, but my response to anyone who doesn’t like a clean, meticulously-picked 12-string is spelled ESAD, FWIW.

arl > RamblinRover Luxury-Yacht 10/17/2016 at 18:37

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Casually chewing gum + Singing like a boss + Playing killer guitar = badass musician.

RamblinRover Luxury-Yacht > arl 10/17/2016 at 18:40

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He also performed Lucky Man at that event:

RamblinRover Luxury-Yacht > arl 10/17/2016 at 18:43

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To add, though - I think Lucky Man is much better in the full ELP version, because it has some nice harmonies.

arl > RamblinRover Luxury-Yacht 10/17/2016 at 18:50

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I do love me some Lucky Man. Beautiful guitar too.

OPPOsaurus WRX > RamblinRover Luxury-Yacht 10/17/2016 at 18:55

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for some reason they remind me of this game:

i cant think of which song it is tho

GenuineAlexReid - The Reidus > RamblinRover Luxury-Yacht 10/17/2016 at 19:53

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They only seem pretentious to those who don’t understand them. ELP play very complicated songs and they (were) all masters at their craft. They are SO good.

Rusty Vandura - www.tinyurl.com/keepoppo > RamblinRover Luxury-Yacht 10/17/2016 at 20:06

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You’d probably have an answer for this one; I’m curious too:

http://oppositelock.kinja.com/what-sets-apart-the-sounds-of-starter-motors-1787904052

JeepJeremy > RamblinRover Luxury-Yacht 10/17/2016 at 20:18

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ELP rules!

RamblinRover Luxury-Yacht > Rusty Vandura - www.tinyurl.com/keepoppo 10/18/2016 at 09:40

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Turbocharged Squirrel had the start of a large part of the answer - gear train noise. Straight cut gears, no matter how well machined, make repeating slip noise which is related in pitch to the rate at which the teeth are passing by. There’s pretty much no way around this, because helical gears experience thrust, and would require larger gears to transmit power (and a larger starter), either a clutch on the starter, constant engagement of the starter for use as a generator, or some way to forcibly engage or disengage against the “pull” of the helical drivetrain.

So, straight gears it is. If you’re dealing with a starter that will spin the motor at 200RPM, and you assume that a “tick” or “chirp” of noise happens at each tooth, a flywheel with 90 teeth would have *some kind of noise* at 300Hz and multiples thereof. Probably an overtone at 600Hz, 1200Hz, and so on. Here’s 300Hz:

The properties of the chirp or tick produced depend on the gear pressure angle and the force between the two teeth, which depends on the width of the tooth vs. mechanical advantage of the starter vs. overall engine resistance (compression vs. rod length ratio vs. stroke vs. bore vs. number of cylinders). Any of those factors varying for the same starter will have the starter spinning at different speeds and with different tooth pressure, and the flywheel, bellhousing, and other elements will amplify or suppress how it sounds just like an acoustic instrument.

In short, the differences in pressure and frequency of repetition could be as different as using the same bow on a violin, a viola, a cello, and a double bass.

Okay, so that’s (as I said) a large part of the answer, but it’s not the whole. If you have a starter with a gear drive (as some are for larger engines, or to reduce electric motor size for a small engine), then that gear drive will make noise as well. Might be at ~3/2 the frequency or so - regardless, that will be present as an overtone, subject to the same pressure and other variable factors. Even that is not the only pitch you’ll hear, however. There’s one that’s easy to leave out, and that’s *motor* whine. The vast majority of starters are not brushless, which means they have a discrete number of active states for their windings, based on the brush geometry.

Even with overlap, there will be a little bit of a jump - contact 1 will be active as well as 2, 1/2/3, 2/3, 2/3/4, etc. If the motor is unloaded, then it will spin pretty freely without this being of much import, but if the motor is under load, there will be a little bit of pulsation in power experienced by the armature, leading to - you guessed it - another overtone, dependent on the load on the motor, and in some kind of fixed ratio to the rest. Say, 18 brushes, 36 brush states, 16 tooth gear starter -> 2.25 times the frequency of the gear noise, which if your base note is an A, would be ~C, one octave up, with probably an undertone of C in the same octave. Actually pretty close to being in harmony.

Remember as well that different frequencies can add or subtract to a total perceived waveform, and the starter is making it easy for this to be the case because the different sources of noise are all mechanically linked - in fixed ratio to one another. To add to this, you have the weight of the flywheel and engine resistance affecting the rate of rise of pitch and fall of pitch as the starter operates, and a whole host of noises that can be made by a mechanical engagement by the solenoid (usually a “clunk”) or a swish-crash noise made by a spring-screw cam.

It’s nearly a miracle two starters ever sound alike.

Rusty Vandura - www.tinyurl.com/keepoppo > RamblinRover Luxury-Yacht 10/18/2016 at 15:13

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You must have spent an hour on this. I would have opined that starters sound similar except for the old school Mopar starters.

RamblinRover Luxury-Yacht > Rusty Vandura - www.tinyurl.com/keepoppo 10/18/2016 at 15:25

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I didn’t spend too long on it - I didn’t need to do any actual fresh research other than calculating the pitch, pulling a sound sample, and confirming that 1.25x frequency was roughly a four semitone jump (which is actually 1.26, if we’re picky). Broadly similar, yes. The same to a trained ear, not at all. I even left out one point, which is that an older car with an oversized and slow starter and low compression can surge in time with the compression strokes if it’s a 1-4 cylinder...

At any rate, there are some large engine size and decade differences, and a lot of variation. Your Mopar starter example is a small motor at high speed with higher pitched motor noise + a secondary drivetrain whine and a slightly lower main gearset noise. Enough small things are different to add up to a big difference.

Rusty Vandura - www.tinyurl.com/keepoppo > RamblinRover Luxury-Yacht 10/18/2016 at 21:22

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Thanks for the explanation. I’d often wondered about it.