Does the M4 have fake engine sounds piped through its radio speakers ! I hope not !

[Boss330]

One key issue regarding active sound seems to be missing from the discussion here... Which is WHY did BMW feel the need to employ active sound?

The answer can be found here:

http://f80.bimmerpost.com/forums/sho...d.php?t=979417

What characterises the sound of a naturally aspirated engine as employed until now in the recently superseded BMW M3?

A naturally aspirated engine has relatively unobstructed lines both from the air intake and to the exhaust systems. A small proportion of the sound that the driver perceives as an acoustic indication of the engine load level in the interior of the vehicle comes from the direct transmission of structure-borne engine noise, while the majority of the noise is transmitted through the air directly from the intake tract; however the noise level is damped to an extent by a combination of the long intake distance and the air filters. In the case of a naturally aspirated engine, this damping can be decreased further by fitting a larger valve to the air box, thus acoustically dethrottling the air intake – as is the case in the BMW M3 CSL for instance. The resulting acoustic effect is very positive.

The situation is similar on the exhaust side of the engine. Only the length of the exhaust tract and the silencers reduce the combustion noise emanating from the engine.

A naturally aspirated engine offers a very broad-banded frequency spectrum, which is useful when it comes to developing acoustic characteristics. A large engine speed range combined with many cylinders and a large engine size have a further positive impact on the available fundamental sound spectrum.

What is it that distinguishes the sound of a turbo engine from that of a naturally aspirated design? And why is this so?

The acoustic properties of a turbo engine represents a great challenge to sound designers.

The turbo charger's paddle wheels that are located in the air intake and exhaust tracts are effectively a barrier that blocks off intake and combustion noise.

As a result, the airborne noise transmitted from the intake is virtually eliminated. And this is immediately noticeable in the interior of the vehicle. Only the relatively weak structure-borne sound transmission remains intact.

The situation is similar on the exhaust side: all combustion gases that flow through the exhaust turbine are subjected to extremely high acoustic damping. Only those exhaust gas flows that are not needed for the turbo charger and which pass through the waste gate past the charger produce a combustion sound that can be utilised. However, these are precisely the acoustically relevant exhaust gas streams that are reduced still further to facilitate the outstanding response characteristics of the M TwinPower Turbo inline six-cylinder engine of the new BMW M3 and BMW M4.

This all sounds somewhat complicated...

Maybe the following example will make it all a bit clearer:

If you imagine a hall (the space beneath the bonnet) in which an orchestra of many different instruments (the engine) is playing. Some of the instruments are able to produce both low and high sounds, i.e. they have a uniformly good bandwidth or a broad sound spectrum.

However, alongside this hall is another, separate hall (the passenger *******, which is joined to the first hall through different sized doors (the body, the air intake tract and the exhaust system). In the case of a naturally aspirated engine, most or at least many of these doors are open, which means that the driver in the room next door can still hear a large frequency band of the sounds produced.

However, in the case of a turbo engine, it is as if the majority of these doors were closed. You can hear something – maybe the basic character of the music as it plays (the combustion) – but the audible portion is restricted to the low-frequency range. A large section of the acoustic frequency spectrum is lost through the turbo system.

However, manufacturers have begun taking systematic measures to compensate for this problem.

The new BMW M3 and M4 employ highly modern technologies.

And what are they?

Ever since turbo engines were invented, sound designers have devised various methods of restoring some of the lost engine sounds to the interior of the vehicle. In the case of sports engines, this is not only important from the point of view of emotional stimulation, but, as we will see in a moment, it is also an important element of acoustic feedback from the car to the driver.

The first stage of development comprised mechanical systems. The vehicle interior was coupled to the high-pressure side of the engine beyond the turbo charger through a membrane. These systems were already relatively effective. However, by and large, the acoustic curve followed the torque progression of the engine.

On the other hand, drivers with sporting ambitions prefer to have an acoustic progression that reflects the actual power being emitted from the motor, as with naturally aspirated engines. It was for this reason that in the wake of the mechanical systems, the first electric sound systems were developed and employed by many among the competition. They involved screw-fitting a so-called shaker to the body of the car. The shaker is a kind of mechanical actuator that can be used to transmit vibrations into the body (e.g. the A column). These vibrations can then be felt in the passenger space.

However, the new BMW M3 and BMW M4 meanwhile use a more intelligent system. The technology employed here makes it possible to restore the sound that is actually produced, albeit damped by the turbo system, and render it audible in the passenger space. This can only be done systematically in those areas in which excessive damping takes place, but the driver desires and requires such acoustic feedback to support or more-sport oriented driving style.

By adopting this approach, it is possible to give the driver a very precise impression of the engine's load conditions. This enables the driver to use his ear as a guide, in the same familiar way as with naturally aspirated engines; after a certain period of acclimatisation, he is able to change gear at the required engine speeds, based on the acoustic feedback received from the engine speed/load conditions, without having to look at the tachometer. This is also important because while the torque plateau offered by turbo engines is broad, it breaks off abruptly when the engine speed becomes too low or too high.

To return to the orchestra analogy: we systematically open certain doors to bring the music to the audience.

Code out the active sound, and you loose the "drive by ear" input provided by the active sound system. Why want to change to a mono sound system when you can have the hi fi surround system?

[Racer20]

Not that this will put the argument to rest, but I want to clarify/explain some of BMW's statements that seem to be creating confusion.

All the argument of whether its recorded or if there's a mic is missing the reality:

It's neither.

All sounds are made up of a wide spectrum of frequencies from deep bass to high frequency treble. A particular noise will have a different mix of frequencies at different levels, which can be measured. For example, imagine the below plot shows the S55 intake noise WITH NO TURBO at a certain rpm/throttle/load condition.

(This is just a random frequency plot, not actually the S55)


Now, imagine that this one is the same measurement WITH the turbo piping in place.



See how the sound is attenuated significantly between 100 and 1000Hz? Now, the engineers can analyze this data to determine what frequencies are beneficial for the auditory feedback from the driver and add them back in. Not with a recording or a mic, but with a synthesizer. (link)

Think of an electronic keyboard. They can imitate lots of different instruments and sounds pretty well, not through a recording, but by synthesizing the sound itself. It layers many different types of sound waves on top of each other to get the desired result based on what keys the musician plays. That's exactly what's happening here, except the keys are the throttle, load, and rpm conditions that the driver is asking for.

It's no more "fake" than your favorite band playing an electric guitar through a PA system rather than an acoustic guitar with no amplification. It's real-time synthesized sound designed to replace the frequencies that are over-attenuated by the turbo and sound deadening.

[myzmak]

Originally Posted by Hoopumpers

Active sound in my F10 M5 was all the rage with journalists (and I agree that philosophically it's lame), but in reality you couldn't hear it at all. It was just a non-issue.

In the M3/4 it's pretty offensive. It's intrusively loud in my opinion. Drive in comfort throttle, then switch to sport plus. It's very noticeably louder. It sounds "good" but is obviously synthetic, and I gotta be honest...that bugs me.

Originally Posted by M4TW

Your offensive reaction might be a placebo effect. In Sport and Sport Plus a valve opens in the muffler to allow the exhaust gasses to pass more directly through the muffler and the sound is naturally louder.

Interesting, because the majority of reviews I have read said the opposite: much more noticeable (and less enjoyable) in F10.

I think @m4Tw is right - what you are hearing is just the loud exhaust note which gets louder in sport/sport +

[Andrew115]

synthesized - is the answer. I believe Racer20 nailed it as usual.

[myzmak]

Originally Posted by Andrew115

synthesized - is the answer. I believe Racer20 nailed it as usual.

I still prefer my explanation of the little elf hidden inside the car BUT, fine, I guess if I wanted to be a scientician or rocket surgeon about it, I would have to admit @racer20's answer is maybe more accurate.

....and the rationale is precisely as @boss330 stated.

...and I stand by my earlier comment that, although some have coded it out, there has not been a hallelujah chorus (heh) of those who have done so.

[Andrew115]

Originally Posted by myzmak

I still prefer my explanation of the little elf hidden inside the car BUT, fine, I guess if I wanted to be a scientician or rocket surgeon about it, I would have to admit @racer20's answer is maybe more accurate.

....and the rationale is precisely as @boss330 stated.

...and I stand by my earlier comment that, although some have coded it out, there has not been a hallelujah chorus (heh) of those who have done so.

I want to turn it up louder is better right?

[M4TW]

Originally Posted by myzmak

I still prefer my explanation of the little elf hidden inside the car BUT, fine, I guess if I wanted to be a scientician or rocket surgeon about it, I would have to admit @racer20's answer is maybe more accurate.

....and the rationale is precisely as @boss330 stated.

...and I stand by my earlier comment that, although some have coded it out, there has not been a hallelujah chorus (heh) of those who have done so.

Racer20's explanation has me thinking that Active Sound in the F80/82 is a lot like a hearing aid that allows the listener to hear frequencies the turbo plumbing otherwise deadens.

"But I don't want no stinken hearing aid when I'm driving!"

"BUT IT WILL HELP YOU HEAR THE ENGINE BETTER GRAMPS"

"What?"

[myzmak]

Originally Posted by Andrew115

I want to turn it up louder is better right?

WHAT?

I can't hear you over this damn racket.....!?

[Racer20]

Originally Posted by myzmak

...and I stand by my earlier comment that, although some have coded it out, there has not been a hallelujah chorus (heh) of those who have done so.

EVERYONE who has ridden in my car has commented on how awesome it sounds. None of them know it has active sound, and none of them really care when I tell them.

[Andrew115]

Originally Posted by myzmak

WHAT?

I can't hear you over this damn racket.....!?

All this synthesis is making me want to synthesize

[myzmak]

Originally Posted by Andrew115

All this synthesis is making me want to synthesize

and BLAMMO! right back to Hegelianism and early German existentialist philosophy.

Will @m4tw come back with his beloved Kierkegaard? Whither the nihilism of Nietzsche?

I guess we now how it was that Kraftwerk came from Germany. Even in having a conversation about a performance car, it comes back to synthesizing and existentialism.

[M3guy3]

Originally Posted by Racer20

EVERYONE who has ridden in my car has commented on how awesome it sounds. None of them know it has active sound, and none of them really care when I tell them.

most people this is not going to be a issue with. specially non car people.

[gthal]

Originally Posted by Racer20

EVERYONE who has ridden in my car has commented on how awesome it sounds. None of them know it has active sound, and none of them really care when I tell them.

Originally Posted by M3guy3

most people this is not going to be a issue with. specially non car people.

IMO, it is a placebo effect. People who know it is there try to listen for it and believe things they hear are artificial (like the car being louder in Sport mode when, in fact, it IS louder from the exhaust ). If someone drove in the car, car person or not, and they didn't know then I bet they would never suspect it is there.

[Hoopumpers]

What's funny to me is that when active sound was announced for the F1x generation, the entire M3 board lit up with screams of laughter and poser comments.

Now we're fanboys over here and it's all good? I think I'm the only one in this thread who has criticized it. So strange.

Anyway. It's really not a big deal. Moving on...

[jbraslins]

had mine coded out yesterday. good news: it sounds exactly as it did before in terms of thr cars sound, tone, freuqency etc. just a lot quiter across entire rpm range. means bmw is not giving us any fake music, just making it louder.

bad news: gonnna code it back on. car is just too quiet without it. i ended up crusing 1500 rpm higher than i did before, wasting gas.

[JRV]

Originally Posted by jbraslins

had mine coded out yesterday. good news: it sounds exactly as it did before in terms of thr cars sound, tone, freuqency etc. just a lot quiter across entire rpm range. means bmw is not giving us any fake music, just making it louder.

bad news: gonnna code it back on. car is just too quiet without it. i ended up crusing 1500 rpm higher than i did before, wasting gas.

Was it 2% quieter?

[Sir Loin]

Originally Posted by jbraslins

had mine coded out yesterday. good news: it sounds exactly as it did before in terms of thr cars sound, tone, freuqency etc. just a lot quiter across entire rpm range. means bmw is not giving us any fake music, just making it louder.

bad news: gonnna code it back on. car is just too quiet without it. i ended up crusing 1500 rpm higher than i did before, wasting gas.

Very good to know. Thanks!

[jbraslins]

Originally Posted by JRV

Was it 2% quieter?

I don't have any kind of real gear to measure and tell you that, I can only guess. I also don't think it's a linear decrease across entire rpm range.

I can def say it's more than 2% 20 or 30 maybe? Who knows.

To my ears, it seemed that bottom half of rpm is where most of the changes are. 1.5k - 4k rpm car sounds way to quiet.

At 3000 rpm it sounds about the same as 1800rpm with active sound on. With peak torque kicking in at 1800 rpm, there's just no need to cruise above 2k.

[Hoopumpers]

^ great info. Thx

[JRV]

Originally Posted by jbraslins

I don't have any kind of real gear to measure and tell you that, I can only guess. I also don't think it's a linear decrease across entire rpm range.

I can def say it's more than 2% 20 or 30 maybe? Who knows.

To my ears, it seemed that bottom half of rpm is where most of the changes are. 1.5k - 4k rpm car sounds way to quiet.

At 3000 rpm it sounds about the same as 1800rpm with active sound on. With peak torque kicking in at 1800 rpm, there's just no need to cruise above 2k.

Got it thanks. Yea 2% would be indistinguishable. Your numbers sound a lot more credible and realistic

[RickMonet]

Originally Posted by jbraslins

had mine coded out yesterday. good news: it sounds exactly as it did before in terms of thr cars sound, tone, freuqency etc. just a lot quiter across entire rpm range. means bmw is not giving us any fake music, just making it louder.

bad news: gonnna code it back on. car is just too quiet without it. i ended up crusing 1500 rpm higher than i did before, wasting gas.

THANK YOU!!!

This is the first I have read from someone who actually coded AS off - very helpful info.

It appears like on/off makes a noticeable difference - so now we have a choice.

[AreOut]

Originally Posted by Racer20

EVERYONE who has ridden in my car has commented on how awesome it sounds. None of them know it has active sound, and none of them really care when I tell them.

well if you let the high-rev V8/10 sound through the speakers they would say it sounds even better

the thing is it's fake but it's not deal-breaker as long as it could be coded off, the stupid thing is that BMW doesn't let people just select it from iDrive