How much can be reverse engineered from sound ?

[lordvader88]

given the task to make the machine that made this amazing sound, what wound the best science of today do ? or i suppose they would guess it's an f1 engine and just start there

[lordvader88]

i wonder what it looks like on an o-scope

[windsmurf]

i wonder what it looks like on an o-scope

Audacity

[Audioguru]

The dinky little V6 engines on today's F-1 cars do not sound like that. But there are many stupid noisy cars and motorcycles in my city or they drive through my city and they sound deafening like that.
I wonder why many cars make almost no noise?

[Brumby]

Very simple.  It's the exhaust system.

Some years ago I spent a couple of years in a "sea-change" job working for a mechanic.  He was an approved examiner for several things, including noise pollution.

One day, a Ferrari came in having been reported for noise and even at idle, the sound level nearly cracked the limit - but it did sound sweet.  The exhaust system was a custom/after market job worth more than $10K and it was suggested he refit the factory exhaust.  He did this and came back - but it failed the sound test.  Turns out that the factory system had vanes that could provide a more direct (and thus noisier) path for the exhaust gases when high performance was required, instead of the more circuitous and quieter path for sedate motoring.  This is what killed his chances of passing  the test.

He went away once more and had these vanes disconnected from the control system and fixed in position for the circuitous path.  This time, the vehicle passed the test - just - but it sounded like and asthmatic dog with a hessian bag over its head getting strangled.  The sound was just "wrong" in every way imaginable.  It did not belong to a Ferrari.

And it was all affected by just the exhaust system

[Bud]

I must be missing something...What is so beautiful in this sound?  To me it sounds as a boring gigantic mosquito 

[floobydust]

Some car makers actually hire sound engineering firms to do the exhaust design, to make the sound unique and have signature harmonics.

Automobile exhaust systems are resonant systems. The exhaust manifold, main pipe, resonator, catalytic converter, muffler - all can be modelled using electrical equivalence i.e. RLC properties. A cylinder fires, a pressure wave propagates down the pipe and can "tug" other cylinder's pressure pulsations.
To get good scavenging with minimum back pressure, and a resonance matching the engine's needs to get a flatter or peaky power curve is the goal.

[Brumby]

If you want to understand just how much the exhaust system does, try driving a vehicle with bits of it missing...

The abovementioned mechanic did LPG conversions and sometimes there would be a need to alter the path of the exhaust system to get around the LPG tank.  I was the one usually chosen to drive these vehicles over to the exhaust place - and let me tell you, you get a REALLY good first hand lesson in the accoustic output of even the most moderate engine - especially when under load.  As a result, my driving in these situations was extremely conservative - but there was still a bridge over a railway that had a steep approach and the noise was intense.

Sometimes the only bits of the exhaust still attached were the manifold, engine pipe and catalytic converter.  BIG noise!  (and, yes, I was constantly looking in all directions for any police interest - which I never encountered, thankfully)

[CJay]

Dunno Bud, maybe different people like different things?

A recording of the sounds makes my neck tingle, I know from having been in the pits when F1 cars are being started and warmed up that the sound and feeling makes my whole spine tingle and makes me smile.

A lot.

@floobydust, I think all car manufacturers who build vehicles with IC engines have sound engineers these days, there were pretensions to engine 'note' in pretty much all of the 'performance' model brochure hype when I was looking at buying a car last year, it almost reads like audiophool reviewers wrote some of them.

The resonant thing has long been known about by people who design performance cars and bikes (have a feeling the bike guys were on the money first), 2 stroke motorcycles have made use of it since forever and there are some amusing stories of Suzuki and Honda 'borrowing' technology from European bike manufacturers way back in the 1950s, I'd think it was known about even earlier than that by some.

[james_s]

I think one of the nicest sounding engines I've heard is the Bristol Centaurus sleeve valve radial. It's a unique sound with no valve noise.

[CJay]

All those big old aero engines are fantastic, scary as all get out when starting, the flames from the exhaust when you're sat in what is essentially a fairly small aluminium box filled with ammunition and fuel... 

[ebastler]

given the task to make the machine that made this amazing sound, what wound the best science of today do ? or i suppose they would guess it's an f1 engine and just start there

While I am impressed from an engineering perspective that one can build a macroscopic machine which runs reliably at that high rpm (well, at least reliable for the duration of a race), I personally hate the sound.

If you want to enjoy that sound at home, I recommend buying a model aircraft engine. Better check with the neighbors first. 

[Rerouter]

The acoustics is from the pipe length and shape, At a guess you would want to analyse what harmonics and frequencies your chasing, compare to what your starting with, and then model a pipe/cavity to amplify or suppress the harmonics to reflect what you are chasing. once you have that down pat it would be a matter of getting it manufactured, as it would likely be a complex composite shape it may require metal sintering, or just a whole bunch of metal working.

[tszaboo]

I must be missing something...What is so beautiful in this sound?  To me it sounds as a boring gigantic mosquito 

Yes, unfortunately F1 doesnt sound that all that good anymore with the recent changes.
Typically on the qualifications day, they have Porsche supercup, Formula 3000 and other races, those sound better than F1. To bad, it just feels like just watching a bunch of random people driving around, unlike F1. No offense to those random people.

[David Hess]

To get good scavenging with minimum back pressure, and a resonance matching the engine's needs to get a flatter or peaky power curve is the goal.

Yep, it sounds like typical tuned headers without any sort of baffle plus the Doppler shift from high speed.

[amyk]

I must be missing something...What is so beautiful in this sound?  To me it sounds as a boring gigantic mosquito 

Same, I like something deeper and more "grumbly":

[Psi]

I always liked the feels of this sound.
It starts at 1:00

[T3sl4co1l]

If you want to understand just how much the exhaust system does, try driving a vehicle with bits of it missing...

The abovementioned mechanic did LPG conversions and sometimes there would be a need to alter the path of the exhaust system to get around the LPG tank.  I was the one usually chosen to drive these vehicles over to the exhaust place - and let me tell you, you get a REALLY good first hand lesson in the accoustic output of even the most moderate engine - especially when under load.  As a result, my driving in these situations was extremely conservative - but there was still a bridge over a railway that had a steep approach and the noise was intense.

Sometimes the only bits of the exhaust still attached were the manifold, engine pipe and catalytic converter.  BIG noise!  (and, yes, I was constantly looking in all directions for any police interest - which I never encountered, thankfully)

Had my exhaust replaced recently, had to limp around town with nothing on while they were getting parts in.  Even the weedy engine in my Toyota sounds like a hotrod* when it's loud and open like that.

*A hotrodded lawnmower, to be more honest / accurate.

Also quite a difference; the previous system I had, was welded from pipes and parts.  In particular it was missing a mid-line resonator.  Never quite sounded right.  (This time around, it's all aftermarket or OEM parts, close enough to original. Sounds about right.)

Also a little surprising how much, and how little, difference can be made from little leaks here or there.  Rusted out pipes tend to get loud, and add a rougher sound with more hiss (modulated hiss -- turbulence on the pulses).  Sound from underneath or behind the vehicle tends to carry pretty well.  OTOH, leaks in the engine bay don't seem to do much, presumably as the sound is forward-facing and reasonably well absorbed and scattered by everything in there.  (They weren't able to seat the downpipe quite right so I had this going on, before getting it re-checked.)

Tim

[digsys]

PPFFTTTTTTT These guys have it all sown up !!
https://www.youtube.com/watch?v=udf7w7ZjnXg&feature=youtu.be

[james_s]

Also a little surprising how much, and how little, difference can be made from little leaks here or there.  Rusted out pipes tend to get loud, and add a rougher sound with more hiss (modulated hiss -- turbulence on the pulses).  Sound from underneath or behind the vehicle tends to carry pretty well.  OTOH, leaks in the engine bay don't seem to do much, presumably as the sound is forward-facing and reasonably well absorbed and scattered by everything in there.  ]

I wonder if leaks in the engine bay tend to be higher pressure, lower velocity? I've had blown exhaust manifold gaskets a few times and it makes a sharp tick-tick-tick sound vs the much deeper hotrod sound when the muffler is shot or missing.

[Zero999]

The dinky little V6 engines on today's F-1 cars do not sound like that. But there are many stupid noisy cars and motorcycles in my city or they drive through my city and they sound deafening like that.
I wonder why many cars make almost no noise?

I agree. I hate noisy cars an motorbikes. They should be banned.

I can see the need for some noise and electric cars can be too quiet, as people don't hear them coming, but a lot of it is excessive.

[Circlotron]

A good V8 at 9000+ rpm sounds pretty cool IMHO.

https://youtu.be/fbTRaDQ1tJA

[mikerj]

given the task to make the machine that made this amazing sound, what wound the best science of today do ? or i suppose they would guess it's an f1 engine and just start there

While I am impressed from an engineering perspective that one can build a macroscopic machine which runs reliably at that high rpm (well, at least reliable for the duration of a race), I personally hate the sound.

If you want to enjoy that sound at home, I recommend buying a model aircraft engine. Better check with the neighbors first. 

A Ferrari F1 V12 engine sounds nothing like a model aircraft engine.  I've heard people suffering from a broken exhaust on their car with a wheezy four pot engine and say "it sounded like a Ferrari".  Is a significant proportion of the population unable to distinguish different sounds?

I think one of the nicest sounding engines I've heard is the Bristol Centaurus sleeve valve radial. It's a unique sound with no valve noise.

What a lovely noise, I could listen to that all day   

[Richard Crowley]

In 1994, Harley-Davidson filed a sound trademark application for its distinctive V-twin engine sound. It realized that if it could capture its own sound, it could distinguish the brand at every point of customer interaction. Just like a visual logo, the most essential qualities of a sound logo are uniqueness, memorability, and relevancy to the brand promise.

https://en.wikipedia.org/wiki/Sound_trademark#Sound_logos

[james_s]

I also thought the race engine in the first video sounded a lot like a model
Airplane engine, high pitched whine, very short stroke, very high RPM, it's not a sound I find pleasing at all but to each their own.