Different sounds and intervals between engines, or: what causes an engine's character?

[Darkone55]

Hi,

So this may be an odd question but it's something I've been wanting to get to the bottom of for a long time now. I'm a composer and I've been fascinated with the sound of a V10 engine. A few years ago I found that the V10 has a major 3rd interval in its sound. Ever since, I've been wondering what exactly causes this to happen. My guess it has something to do with the order in which the pistons are firing, but I have no idea how.

Let's get to the basics first. I've looked mainly at V6, V8 and V10 engines. I have found that V8 engines have an octave interval, V6's have a fifth interval and V10's have a major 3rd interval (actually an octave and a 3rd). Apparently there's a relationship between these engines and the harmonic series.

From the sound of it, a V6 could be a 3 cylinder engine with 2 cylinders firing at the same time. A V8 is very similar to a line 4 (or maybe 2 cylinder?) and a V10 is like a line 5. After some more analysis I found a clear relation between the amount of cylinders and the harmonic series:

V10 and line 5: loudest harmonics are: harmonic 5, 10, 15, 20..
V8 and line 4: loudest harmonics are: 4, 8, 12, 16, 20..
V6: loudest harmonics are: 3, 6, 12, 15, 18..

In all engines I found that apart from these harmonics the octaves would sometimes be pretty loud as well, or very soft. Also, most harmonics would be in every engine, no matter what type. Sometimes the fundamental would be missing. But variations like these could be due to the recording equipent (mics not picking up certain frequencies, pre-amps, even wind). So it's not so much that only the line 5 or V10 have a major third interval, it's more that it is way more prominent in these engines as opposed to 4, 6 or 8 cylinder engines.

For the V10 and V6 it seems to make sense: they're divisible by 2, giving 5 and 3. But 4 is divisible by 2, even though the louder overtones are ever 4th harmonic. Could this mean that in a 4 cylinder engine, none of the pistons fire together?

In any case, I have no idea what exactly causes this relationship. If this has to do with the order in which the engines are firing, how do these frequencies come about? If the pistons fire in an even way in time, you'd have just the frequency of this firing. In all this I just assumed that the firing of the pistons makes the noise, but could there be more?

Hopefully some people here know a lot more about how engines work and could enlighten me on this.


For anyone interested in my analysis: http://v10.basbouma.nl/V10%20harmonic%20series.xls

And I also uploaded some of the spectrums I analysed (the clearest spectrums):
Ferrari F2002 V10
Audi R8 LMS V10
Porsche 991 V6
Alfa Romeo 4C line 4


Thanks!

PS. related to this but not quite the same question. Why does an American muscle V8 sound so less 'tight' from a V8 racing engine?

[J.A.W.]

Hi,

So this may be an odd question but it's something I've been wanting to get to the bottom of for a long time now. I'm a composer and I've been fascinated with the sound of a V10 engine. A few years ago I found that the V10 has a major 3rd interval in its sound. Ever since, I've been wondering what exactly causes this to happen. My guess it has something to do with the order in which the pistons are firing, but I have no idea how...

Thanks!

PS. related to this but not quite the same question. Why does an American muscle V8 sound so less 'tight' from a V8 racing engine?

D-1, I suggest you do a basic literature search in this forum section on crankshaft configuration, firing orders, &
intake/exhaust pipe groupings.. even the basic US 'muscle car' V8 units offer significant differences in these..

& for really 'musical' sounds, check engines which feature even-firing multiples of 3 cylinders..

Here are a selection..

3: https://www.youtube.com/watch?v=1N5rm0glYwY
6: https://www.youtube.com/watch?v=htHgs10AHXU
12: https://www.youtube.com/watch?v=M9I7GWllPFY
24: https://www.youtube.com/watch?v=70Sd8h3XXvU

[Tommy Cookers]

in 99.99% of 4 cylinder engines the firing intervals are equal
the rest are Yamahas with crossplane cranks giving uneven firing - (NB there is not simultaneous firing)
but the uneven intervals of Yamaha trick the ear into hearing as a 'looser' or lower pitched sound than equivalents from the 99.99%

all (90 deg) V8s have equal firing intervals overall
but 1% have flat ie single-plane cranks and each banks exhaust system receives pulses at even intervals
conspicuously 99% are traditional V8 crossplane crank ie Detroit style - the banks exhaust receives pulses at uneven intervals
this uneveness tricks the ear into hearing a lower ?, 'looser' or 'calmer' sound than otherwise
(the same mechanism applies to flat 4s but is unattractive, the 'loosening' makes them sound like a twin cylinder engine)

the traditional V twin motorcycle (H-D-style - only slightly uneven intervals) sounded 'calmer' than an equivalent even firing twin
though we now have twin layouts suitable for even firing but given uneven firing cranks, in part for balance reasons


the acoustic signature may tell us how suited a performance engine design is to exhaust and inlet 'tuning'
tradition says some cylinder counts are better than others
does a strong harmonic represent a frequency at which the cycle cannot use favourable pressures ? (to boost flow)
(maybe eg the F1 V10 was not so clever ?? and maybe the Renault 110 ? deg V10 was ???)

[J.A.W.]

in 99.99% of 4 cylinder engines the firing intervals are equal
the rest are Yamahas with crossplane cranks giving uneven firing - (NB there is not simultaneous firing)
but the uneven intervals of the Yamaha trick the ear into hearing as a lower pitched sound than equivalents from the 99.99%

No T-C.. that "99.9%" figure is simply ludicrous.. ..unless you rely on a technically spurious 'numbers made' fiction..
.. fact is.. there are numerous design examples of V4/Sq 4/inline 2T/boxer 4 - mills that are not in the 180' 4T category..

[Tommy Cookers]

you don't accept the word 'are' means/implies current or recent (4 stroke) engines such as the OP has kindly presented ?
fwiw I am attempting to study these data

btw your 'numerous' examples are far from numerous

[Greg Locock]

My chief partner in crime at Lotus spent rather longer than he was supposed to trying to make a 4 cylinder Citreon AX sound like a Corvette. So, he started with the standard antinoise box, and then added harmonics.

As a saxophone player and engineer he thought our many analytical toys would help. Sadly I was busy with more mundane matters and didn't track what he was up to, although an evening playing the sax into an FFT analyser was memorable and informative.

Anyway the upshot was that he succeeded, which led to a few breathless press releases.

The sad truth is unless you are tracking phase information as well, then you will be lost.

[Darkone55]

Thanks for the replies so far!

in 99.99% of 4 cylinder engines the firing intervals are equal
the rest are Yamahas with crossplane cranks giving uneven firing - (NB there is not simultaneous firing)
but the uneven intervals of Yamaha trick the ear into hearing as a 'looser' or lower pitched sound than equivalents from the 99.99%

all (90 deg) V8s have equal firing intervals overall
but 1% have flat ie single-plane cranks and each banks exhaust system receives pulses at even intervals
conspicuously 99% are traditional V8 crossplane crank ie Detroit style - the banks exhaust receives pulses at uneven intervals
this uneveness tricks the ear into hearing a lower ?, 'looser' or 'calmer' sound than otherwise

...

the acoustic signature may tell us how suited a performance engine design is to exhaust and inlet 'tuning'
tradition says some cylinder counts are better than others
does a strong harmonic represent a frequency at which the cycle cannot use favourable pressures ? (to boost flow)
(maybe eg the F1 V10 was not so clever ?? and maybe the Renault 110 ? deg V10 was ???)

Yea I figured 4 cylinder engines generally don't fire at the same time. I found a few line 4 engine animations:
https://www.youtube.com/watch?v=M1h9eU9YH5o
https://www.youtube.com/watch?v=OGj8OneMjek&t=12s

As for a muscle car V8 my guess is that the bigger cylinder volume causes a lower sound. The uneven intervals makes sense for the loose sound I guess.

The way the harmonics are built up in the different engines seems pretty consistent to me, and I can't see how it has an effect on performance, except that more regular intervals maybe make for a more consistent power output and less torque on the engine..

[Darkone55]

My chief partner in crime at Lotus spent rather longer than he was supposed to trying to make a 4 cylinder Citreon AX sound like a Corvette. So, he started with the standard antinoise box, and then added harmonics.

As a saxophone player and engineer he thought our many analytical toys would help. Sadly I was busy with more mundane matters and didn't track what he was up to, although an evening playing the sax into an FFT analyser was memorable and informative.

Anyway the upshot was that he succeeded, which led to a few breathless press releases.

The sad truth is unless you are tracking phase information as well, then you will be lost.

Hehe. Well, after quite some FFT analysing I found it's not that hard to recreate the general character of for example a V10 engine with just 2 instruments. Having 2 trombones play an octave and a major 3rd apart and then doing glissandi for the revs works really well to imitate it.

I'm not sure if the phase information is really relevant to be honest, the results seem to be pretty clear and there's not much difference in the sound of a 5 cylinder engine compared to a 10 cylinder engine, except that the V10 sounds more 'phat', in the same way that multiple instruments playing the same note sounds more 'phat'. It's a bit of chorus or phasing effect, that's all.

The question isn't so much about how to imitate the sound though (not at the moment, for me), but more about understanding how these sounds come to be. I doubt it's as simple as '5 cylinders fire in the time of 1 crankshaft rotation'. There must be a relation between 2 sounds, but I'm not getting any further than the cylinders.


For the interested, here are 2 examples:
Audi V10 rpm range: http://v10.basbouma.nl/trombones%20v10.mp3
Formula 1 V10 rpm range: http://v10.basbouma.nl/trombones%20v10.mp3

It's not perfect it all I know, as it needs to be way rougher and many sounds like the gearbox whine and such are missing, but it just about brings across the character of the engine..

(sorry if there's a double post, I really wanted to reply but my comments need to be approved)

[J.A.W.]

you don't accept the word 'are' means/implies current or recent (4 stroke) engines such as the OP has kindly presented ?
fwiw I am attempting to study these data

btw your 'numerous' examples are far from numerous

Huh?

Are we discussing designs as actually built.. or sheer 'numbers' of 'grey porridge' 4 cylinder mills..

[J.A.W.]

...Well, after quite some FFT analysing I found it's not that hard to recreate the general character of for example a V10 engine with just 2 instruments. Having 2 trombones...

& for the sound of a hi-po single..
Go back to real classical perhaps.. https://www.youtube.com/watch?v=HKVplvWqXWI

[Tommy Cookers]

@ D
if the engine rpm is regarded as a fundamental frequency then with eg a tuned length exhaust system .....

a single cylinder (per bank) will generate a single induction-favourable reflected pulse in its 2 rev cycle
3 cylinders (per bank) will generate 3 i-f reflected pulses in 2 revs, 4 cyls 4 pulses, 5 cyls 5 pulses etc
much of the pulse energy will be unused and so variously reflected and re-reflected as attenuation is small c. 10%
pulses tend to sort themselves into whole-number frequency multiples or sub-multiples anyway eg as waves in the sea

so the noise signature will have 3, 4 or 5 order harmonics ? (relative to crank rpm)

the engine (and also the car, unless isolated) is vibrating at crankshaft rpm frequency and various higher multiples of that
due to its crankshaft non-SHM motion geometry etc
and the piston motion perturbation by the crankshaft torsional etc vibration at a mix of frequencies etc mostly higher than the fundamental
even the valve operation involves substantial vibration at a mix of frequencies

[Frank_]

lengths of primaries has an effect too tho, even a straight 4 can have some subaru burble


https://www.youtube.com/watch?v=JdvbNvyXsng

[NL_Fer]

Almost al engines fire a single cilinder at a time and the interval between every cilinder is the same. But the sound we hear is mostly from the exhaust and the difference between engines is the timing at which the firing comes together in the exhaust manifold and pipes.

[J.A.W.]

Almost al engines fire a single cilinder at a time and the interval between every cilinder is the same. But the sound we hear is mostly from the exhaust and the difference between engines is the timing at which the firing comes together in the exhaust manifold and pipes.

Not necessarily, since that 'traditional' off-beat V8 cadence is missing from the flat-plane crankshaft V8 types,
& Ferrari, for example, offers a switchable exhaust chamber system, which alters the sound perceived( & loudness) significantly..

Engine intake sounds also contribute, as do associated inputs from audible mechanical functions from turbos & etc,
as well as various 'threshing' sounds emitted by the internal engine workings.. these all give a certain character..

& naturally make for a more interesting aural experience than say.. an electric motor with its 'kitchen appliance' whine..

[Darkone55]

Coming back to the 'muscle-V8' compared to a race V8, check out this example. It's a V12, but (very?) low idle revs it sounds like a muscle car, but when it flies by in high revs it almost has a completely different character: https://www.youtube.com/watch?v=KizrWZk_nMU