I was getting confused by speculative information about the 991 sound symposer and came across this article in SAE vehicle engineering online which I found to be very informative. Thought I'd share it.

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The complex exhaust system of Porsche's new 911 Carrera S has a wide-ranging acoustic capability.

The automotive engineer's vocabulary is typically broad and precise, which makes it intriguing to hear the word "emotion" used increasingly when new technologies are introduced. In the case of Porsche's new 911, emotion was cited by engineers as a key factor in developing the car's acoustic signature.

"Sound was a major design and engineering focus," explained Wolfgang Hatz, Porsche's Main Board Member for Research and Development, who also heads VW Group's powertrain development.

At a recent technology workshop for the 2012 Carrera and Carrera S, Hatz and other Porsche engineers noted that creating a unique sound quality "between the engine and the tailpipe" has been a leading criterion for the 911 ever since the iconic sports car's 1963 debut. For the new Type 991 series (see New generation 911 Carrera), the development team focused on “mechanical engine sounds characterized by high frequencies with tonal elements” together with low-frequency intake noises.

So significant is the 2012 car’s symphony as deemed by Porsche that the interplay between induction and exhaust was part of the car's design and engineering specification. Computer modeling mapping, as well as analysis of the configuration and dimensions of manifolds, pipework, catalytic converters, and mufflers, was carried out at the company’s Weissach Development Center.

The required sonic profile had to satisfy all possible operating states—from engine starting and idling (conveying power without disturbing the neighbors) to wide-open throttle on a racetrack. The goal was not only to deliver the aural “emotions” expected of a 911 but also to provide the driver with feedback about the car’s mechanical status while meeting Europe's 74 dB(A) drive-by noise requirements.

Electronically synthesized noise is not a Porsche solution, so the engineers developed a new Sound Symposer that is standard on both versions of the car. An acoustic channel picks up intake vibrations between the throttle valve and air filter and a membrane incorporated in the channel reinforces the vibrations and transmits them as an engine sound into the cabin. The system is driver activated or deactivated via a “Sport” button that controls a valve ahead of the membrane.

The result is a direct acoustic link between the cabin occupants and the engine, providing optimal transmission of the load-dependent sounds. The sound of gearshifts can also be enhanced.

The Sound Symposer incorporates a tunable Helmholtz resonator to achieve an harmonious sound pattern, damping out unpleasant noise occurring at around 5000 rpm.

If the Sound Symposer is deactivated, an aperture in the air filter housing still allows the basic engine and exhaust tones to be heard—"because we don’t want it to sound boring!” explained Dr. Bernhard Pfäfflin, General Manager of the Noise and Vibration Department.

 

i dont like how it's about same on or off.... only more "deep" drone when on... i want to find a large cork and shove it in the hole... :-/

engine sounds great, pops and burbles stock on S model because of the factory bypass of the side mufflers=great design.

 

I appreciate the effort, but adding weight from sound deadening, and then adding more weight from the sound symposer just to get the sound back in again on demand? What was wrong with the 997?

At least they didn't go the BMW route!

 

Hi Carrera,

Couldnt agree more..this is for me another thing why I dont like the 991 - and will not buy one. Why the hell all this sound symposer thing? Doesnt a GT3 sound good enough? Can you imagine Ferrari or Lamborghini using this too - creating artificially changed engine noise?

The 991 is (should) be a sportscar - and its engine should - must sound like a sportscar without any falsification procedures.

I would even go that far saying that this is a shame for a sports car manufacturer..like the e-steering...even if the difference is much ...

Mclaren, new M6, 458, aventador all have normal steering..so they cant be that wrong. Even BMW took out the e-steering for its M6 now...

 

I drove the 991S on the track and can tell you that for my driving ability the steering is exceptional. I was sceptical but was surprised at its response. This is coming from someone who has had a GT3.

The note of the exhaust is not artificial. The symposer is simply a pipe porting sound to the inside of the car. The exhaust is adjusted so that it sounds nice... that is what exhaust design is also about whether it's Ferrari or others. What I would feel odd about is if the sound outside the car was entirely diffused so as to not be "loud" but the inside is. Overall the note of the 991 is in my opinion one of the nicest in a sports car for everyday use.

 

Hi Haku

thanks for the info..yes - the sound does not really sound artificial..but Im old fashioned (although Im not old at all)..and I prefer more pure things with little technical gimmicks...GT3 or C-GT would be my cars...

A C-GT I dont own yet..unfortunately

 

I can understand where you're coming from. I was so no no about pdk as well. Especially because I really did not like it on a 997.2 C4S I had. Then I tried it on a 991S and liked it. I do think that the GT3 version in a year or so will be something fun.... until then I'll make do with a 991S.

 

After reading this I have no problem with the sound symposer; whereas BMW's "solution" was to employ artificial sounds to make up for the engine's aural shortcomings, Porsche's approach amplifies what already exists; in conjunction with the optional PSE, it sounds phenomenal.

Sometimes people say that the water-cooled cars don't sound as good as the air-cooled cars. My 993 with free-flowing mufflers and the OEM motorsound airbox sounds great, but so does the 991 (imo the best sounding water-cooled 911, notwithstanding the GT3 variants). The 991 GT3 should sound great since it will rev a bit higher and surely have a more aggressive exhaust, but it won't have that unique Mezger resonance / timbre...

 

I agree here thats why I still stick with the 997, but the 991 is a really nice car.

 

Yup, BMW did a horrible job. And while Porsche's solution isn't "fake" sound, it is a total contradiction. They put a bunch of sound deadening into the car which adds a bunch of weight, just to put the sound back in again, adding even more weight. I understand they want the car to appeal to more of a mass market, therefore they'd want the sound deadening, as well as the enthusiast, who would like the noise, but in my opinion the whole system makes no sense, and adds a bunch of weight. Sure Porsche claims the 991 is lighter than the 997, but most 991s actually weigh in more than the average 997, and just imagine how light weight the 991 could be if it didn't have all of these unnecessary features to appeal the Lexus drivers. Rant over, but as much as the 991 is going the consumer route, I still appreciate some people at Porsche's effort to keep the car sporty.