The Changing Sound of the Drive

One of the major aspects of driving is the sounds of the drive — the engine, the road, the environment. Normally, we spend our car time with the windows up, the music on, and the roof in place and closed. This year's unseasonably dry and warm weather has increased the number of “experience the outside” days in the car.

In addition to being exposed to the environment, you also get “live feedback” from the engine and road. This exposure to the sound is the leading factor in the inclusion of sunroofs and convertibles in the car buying marketplace.

Alternatively, in the push for luxury, sound insulation in the cabin has been increasing, and so has the isolation from the sounds of driving. A great deal of the learning experience for knowing when to shift a manual transmission comes from the sound of the engine and the whine of the gears. The new cabin sound proofing is designed to provide isolation from the noise of the rapidly declining roadway conditions and the increased noise from wide low profile tires. This gives the driver and passenger a uniform and balanced environment in which the infotainment system can also operate.

However, there is a downside to this isolation. The lack of exposure to the external sound means a sensory disconnect from what the car is doing other than primary visual cues.

Recently, on a warm day while driving, we heard an uncharacteristic clacking from the engine. Later we checked the engine and found that it was about one quart low on oil — enough to be an auditory change, but not enough to be a warning from the instrument cluster. Similarly, the sounds of wearing belts and brakes are easy to detect by sound, but do not report by most drivers systems until they are at the “replace now” point.

A trend to address the issue of what the engine is doing is to play engine sound through the audio system of the car to the cabin. In some cases it is real sound, such as with the Porsche Sound Symposer solution (see Figure below), but in most it is a pre-recorded “ideal” sound. This faked engine sound from the pre-recorded tracks introduces some driver challenges. While it is beneficial to direct when to shift and brake in “sport” mode for the car, it does not realistically portray the state of the engine in live driving.

Porsche's Sound Symposer solution provides a direct acoustic link between the the sounds of the engine and cabin occupants.

Porsche's Sound Symposer solution provides a direct acoustic link between the the sounds of the engine and cabin occupants.

The push towards higher gas mileage in cars is bringing a big shift in car sounds. Many auto manufacturers are introducing models with three- and five-cylinder engines, which have a unique sound versus that of standard engines.

These new engine sounds have an audio learning curve for experienced drivers. Hybrid and EVs have reduced engine sounds, which almost completely eliminate audible driver feedback. This is a major concern in the event of driving over in-roadway debris, and not knowing if portions of the debris got caught up in the engine and damaged anything. This is also true for EVs as is the case with some of the Tesla fires.

While piping recorded sound into the driver's cabin may provide a “performance solution” for those yearning for the muscle car era and the experience of the sounds of a high-performance supercar while still in a regular person's price range, it does not represent a viable solution for the real driving experience.

1 comment on “The Changing Sound of the Drive

  1. Eldredge
    April 1, 2014

    Maybe one day, cars will be able to use sound signatures to diagnose their own operating parameters, and provide early warning cues to the driver.

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