Sonic Puzzle.

[RANDM]

Ok - you eclectic gathering of divergent interests, I wonder if
anyone has a line on this.
Keeping it simple a Single cylinder engine idling at 1000
Rupums has 500 combustion strokes per minute or 8.3333
Per second.

How come we only hear Putt, Putt, Putt?

Maurie.

[pehayes]

Keeping it simple a Single cylinder engine idling at 1000

What 1,000 rpm?
My Falcone will idle at 200 which is 1.66 fires per second.  Easy to count.

Patrick Hayes
Fremont CA

[oldbike54]

 I prefer chuff chuff chuff , which apparently is the sound that hamster farts make 

 Dusty

[johnr]

I'm not sure about the question Maurie. Are you asking why the ear can distinguish specific sounds 8 times a second?

[Sasquatch Jim]

  Maybe you are not listening fast enough.

[kirkemon]

It's a four stroke right?

[acogoff]

     Could be like sight.  A florescent flashes 60 per second but the eye can only pick up like 16. But then it would be a constant hum instead of put put. A big don't know is my answer.

[Penderic]

Dont know. 

Don't notice that on other cyclic mechanisms.




Hear Putt Putt Putt on full auto? Nope.

[Huzo]

If you watch a digital readout of seconds and look at the tenths, you'll find that you can damn near say, 1,2,3,4,5,6,7,8,9,10 as quickly as the digits change, especially if you don't verbalise, just do it in your head. I guess if you accept that, then one bang every 1/10 of a second is quite discernible to the ear, so one every 1/8 would be easier. I contend that you can easily pick a V twin 4 stroke Guzzi, from a flat twin of equal displacement like a BMW R1100S at same RPM, say 4,000. That being the case (if it is) then your ear is picking up the difference between a bang every 360 deg versus every 450 - 720 deg. It's a drone (BMW) versus a canter or loping beat (Guzzi, Ducati). Just for fun 'cos it's your Winter, if you get a wooden disc, have a 720 deg scale around  the perimeter and spin it on an axle. Whack a nail at 0 deg and 360 deg, spin that and let the nails hit a card as it goes 'round and you'll have the firing intervals of a flat twin 4 stroke. Now replace the nails with one at 0deg and one at 450 deg and spin it again and you'll hear the distinctive loping beat of the V twin. Your ear will thank you for it. The even beat sounds boring, but there's something about a "push" - "drag" rhythm that's fundamentally appealing. Now why would a male think that ????

[Huzo]

It's a four stroke right?

Given the data, could it be anything else ?

[RANDM]

Struth Huzo what you smoking?!!

OkOk - to keep the Velociraptor happy a four stroke single at
1000 Rupums fires 8.3333 times per sec.

Why can't we hear all if them, why do we only hear 3 mabe 4
Per sec?

Maurie

PS - Huzo, can I have some?

[Huzo]

Struth Huzo what you smoking?!!

OkOk - to keep the Velociraptor happy a four stroke single at
1000 Rupums fires 8.3333 times per sec.

Why can't we hear all if them, why do we only hear 3 mabe 4
Per sec?

Maurie Easy big guy !!! For sure you're hearing more than 3 per second. If you listen to a metronome set at 3 beats per second, it's slower than an idling single. Tap your fingers 123123123123 such that every time you get to 1 it's a second apart from the previous 1 , no bloody way will a single idle that slow. And as for what have I been smoking ? Nothing mate, I've always been this stupid. Never smoked, there's only two things I've never put in my mouth and ones a cigarette.

PS - Huzo, can I have some?

[Huzo]

And BTW before I'm labelled a complete tosser, (I'm actually an incomplete tosser), grab your disc that you secretly ran out and made and put 8 nails evenly round the circumference and spin it at 60 rpm (1 rev per second) you'll hear all 8 "bangs" per second and it'll sound like the idling single. Promise!!!Also, no you can't have what I'm smoking, you live on the Mornington Peninsula, you hippies invented the stuff !!!

[charlie b]

The ear/brain can distinguish a lot in the frequency range.  If it could not then music would not exist.

[Phang]

if you place your hand at the exhaust, the puffs are consistent with the putt putt putt...

I don't remember I felt 8.3333 puffs per second on an idling single which lead me to think the exhaust somehow swallow all the bangs and spit out putts.

[Huzo]

if you place your hand at the exhaust, the puffs are consistent with the putt putt putt...

I don't remember I felt 8.3333 puffs per second on an idling single which lead me to think the exhaust somehow swallow all the bangs and spit out putts.

Um...... probably not you'd think, that would involve the system allowing pressure to increase then expel the air at pre determined intervals. You'd need a synchronised valving setup of sorts.

[Huzo]

Struth Huzo what you smoking?!!

OkOk - to keep the Velociraptor happy a four stroke single at
1000 Rupums fires 8.3333 times per sec.

Why can't we hear all if them, why do we only hear 3 mabe 4
Per sec?

Maurie

PS - Huzo, can I have some?

and I believe the expression is "strewth" at least according to Maurie Fields or Chips Rafferty.

[johnr]

and I believe the expression is "strewth" at least according to Maurie Fields or Chips Rafferty.

Phonetically perhaps, but the more correct spelling would be 'Struth.  A somewhat archaic expletive on this side of the ditch though still occasionally used.

As to the original question, Of course you can hear 8 bangs a second! (and that's a fast idling single!) You would individually distinguish sonic pulses at a considerably higher frequency than that.

[trippah]

If it is idling at 1000 rpms, and the power stroke is every fourth stroke, wouldn't that be 250 pops per, rather than 500?

[johnr]

If it is idling at 1000 rpms, and the power stroke is every fourth stroke, wouldn't that be 250 pops per, rather than 500?

Erm... no. Because RPM is revolutions per minute not strokes per minute.  So 1000 RPM = 2000 strokes per minute.  One up and one down per  rev. (thinks: "maybe Trippah is just stirring the pot here!")

[Penderic]

Oddio Illusion!


Hmmm. Do I need to adjust my valves again?

[RANDM]

and I believe the expression is "strewth" at least according to Maurie Fields or Chips Rafferty.

Oh picky picky - settle down Huzo ........ I only gave you a
tickle, nice Shetland but.

Not talking about the different rhythms or beats of different
Engines configurations or about how fast you can count.
Also if you talk twins then it'll be 16.666 per sec if I can do
Addupskies rightish.

Let me put it this way - music and tapping fingers have been
mentioned, try picturing this : dance/trance/disco is basically
all set around 120 Beats Per Minute deliberately, it's a
heightened heartbeat that approximates a fast walk so it lifts
People and makes them want to move.
Now imagine that rhythm doubled and your at a pretty much
Flat out run and that's 240 BPM.
Now double that again and that's what you should hear from
the example. Are you?
This all started listening to classic singles and stuff in a mates
Workshop - I play a bit of music and beats and rhythms are
Instinctive to me. One day the Math occurred to me while
listening and I realised what I was actually hearing seemed
more like a half time beat and it's puzzled me since then.

Best I've come up with is the volume of the Cylinder as opposed
to the volume of the exhaust. They're related in a tuned system
And if say the Exhaust is twice the volume of the cylinder then
perhaps half the combustion detonations are "lost" halfway or
perhaps they overlap and we hear two doubled up as one beat.

Thoughts?

[Penderic]

And, more importantly, how many smoke rings per rpm should a engine reliably produce?

The benchmark ......  https://www.youtube.com/watch?v=q_0xifuTqVA
Puff away, puff puff puff. Yee Haw!

[johnr]

Well hell guys. I found I could reliably hear every crack as rounds exited the barrel of a GPMG at the rate of 1200 per minute,  (an experience I'm sure many of you have shared) so I'm sure there would be no problem with 16 beats a second.

(Sign... Made an appointment with Bay Audiology today.)

[Huzo]

Phonetically perhaps, but the more correct spelling would be 'Struth.  A somewhat archaic expletive on this side of the ditch though still occasionally used.

Yeah here also John. However, I'll not interrupt the jury while they're out on this one. Thanks.

[Huzo]

Erm... no. Because RPM is revolutions per minute not strokes per minute.  So 1000 RPM = 2000 strokes per minute.  One up and one down per  rev. (thinks: "maybe Trippah is just stirring the pot here!")

No John he's actually correct, don't you know anything about engines struth ! That's why there's a spark plug in the sump next to the oil drain, so at BDC you get a power pulse to push the piston back up !!!?

[Huzo]

Oh picky picky - settle down Huzo ........ I only gave you a
tickle, nice Shetland but.

Not talking about the different rhythms or beats of different
Engines configurations or about how fast you can count.
Also if you talk twins then it'll be 16.666 per sec if I can do
Addupskies rightish.

Let me put it this way - music and tapping fingers have been
mentioned, try picturing this : dance/trance/disco is basically
all set around 120 Beats Per Minute deliberately, it's a
heightened heartbeat that approximates a fast walk so it lifts
People and makes them want to move.
Now imagine that rhythm doubled and your at a pretty much
Flat out run and that's 240 BPM.
Now double that again and that's what you should hear from
the example. Are you?
This all started listening to classic singles and stuff in a mates
Workshop - I play a bit of music and beats and rhythms are
Instinctive to me. One day the Math occurred to me while
listening and I realised what I was actually hearing seemed
more like a half time beat and it's puzzled me since then.

Best I've come up with is the volume of the Cylinder as opposed
to the volume of the exhaust. They're related in a tuned system
And if say the Exhaust is twice the volume of the cylinder then
perhaps half the combustion detonations are "lost" halfway or
perhaps they overlap and we hear two doubled up as one beat.

Thoughts?

Ok mate, so what happens if you took the header pipe off and started the engine ?  Now there's no exhaust system but you'd still have no trouble at all discerning individual pulses @ 8 beats per second

[RANDM]

I don't know Huzo - that's one reason I posed the question,
to gather other peoples ideas on it. As I said it puzzles me.

Oh, where I come from ( Northern Beaches of Syd. )
Struth is more correctly spelt 'Struth as an a abbreviation of
An old English oath God's Truth > 'Struth.

Maurie.

[Chuck in Indiana]

 I agree completely, they all have to be there and if one is missing it will be deafening.

:-)

  BTDT.

[Huzo]

I don't know Huzo - that's one reason I posed the question,
to gather other peoples ideas on it. As I said it puzzles me.

Oh, where I come from ( Northern Beaches of Syd. )
Struth is more correctly spelt 'Struth as an a abbreviation of
An old English oath God's Truth > 'Struth.

Maurie.

Oh, ok then Maurie, that's got the ring of truth to it, my apologies to John also. I stand corrected, thanks chaps.