Sound Design

Cars and music go together like little else does. And if you’ve ever had to figure out how to get a dozen or more speakers into a vehicle and make it sound great, you’ll know exactly what we mean.

Obviously, it’s worth it. Whether it’s because we’re “trapped” for the ride home from work with little in the way of outside stimulation or because we want to take full advantage of that precious “alone” time, we can’t seem to live without our tunes.

And just when we thought it might not get any better than the compact disc, technology that’s more than two decades old, along comes DVD audio, with more digital information packed onto the same physical space as a CD.

What does that mean?

An audio revolution.

DVD audio improves every aspect of car audio: much greater music detail; and surround sound (instead of two-channel (left/right) stereo) to really make you feel like part of the show.

Car manufacturers are making the switch for several valid reasons: the technology exists; we’re willing to spend to get it; and they can make money providing it.

High-quality sound ranked number five on a list of 42 desired features in a vehicle according to a J D Power & Associates Global survey. A European survey indicates 50 percent of the population gets its strongest musical experience in a vehicle.

Today’s home-based “5.1” surround-sound systems (five distinct sound “channels” plus a subwoofer channel for very low frequencies) are so complicated to match to a vehicle that they’re now part of the initial design process. Most companies farm-out the necessary audio engineering, tasking suppliers with the role.

Ford Motor Company does so for its most expensive and exclusive vehicles, such as those from Volvo. The division has had a lead role in developing audio and infotainment systems for luxury vehicles from Aston Martin, Jaguar, and Land Rover, all of which have fallen under the Ford umbrella.

Volvo actually introduced Dolby Surround Sound in a car and an in-dash CD-changer way back in 1977 (CDs wouldn’t become widely popular until the mid 1980s), the first 12-inch-diameter subwoofer in 1999 and the upgraded Dolby Pro Logic II surround sound in 2002. Volvo’s 60-person audio engineering department in Sweden has a long-standing relationship with Dolby Laboratories.

The San Francisco-based company’s Dolby Digital Surround Sound technology is the reigning standard, used in more than 40,000 theaters and three million homes around the world.

Martin Lindsay, Director, Licensing Business Development, Automotive Entertainment, for Dolby says his company and Volvo have been working together since 1994 when the center channel speaker was introduced on the C70.

“The goal is to ensure the sound remains faithful to the source, while reducing complexity,” he says.

Most audio is recorded on multiple channels at the source. This information is then compressed into two channels for broadcast or recording onto CD or DVD. Dolby systems sense signals as they arrive from this stereo source and send them to the appropriate channel/speaker.

“Timbre, tonality, dynamics and balance have to be maintained and separation is essential. Getting it as close as possible to the original is the goal.”

The most difficult part of the process, and the reason the system has to be developed at or in conjunction with the manufacturers, is to make sure that all vehicle occupants, no matter where they are seated, hear the same thing.

This is difficult to accomplish mostly because of the tight quarters and the proximity of the speakers to the vehicle occupants.

Traditional two-channel (left and right) stereo systems require a left/right balance control to adjust the sound source for either left or right seat occupants. The addition of rear speakers brings with it the need for another compromise, the fader control. It also means vocals coming from both front and rear, which is unnatural.

Dolby and Volvo introduced the center channel to help solve these “imaging” problems. Just as in a theater or studio, the vocals come from a central source.

Hans Lahti, Technical Specialist, Audio, Volvo Car Corporation is a young engineer with a trained ear and a mission: to provide the most realistic audio experience possible. He explains that meeting that goal is a classic bad-news, good-news scenario.

The challenges include the small space for component location, not to mention location restrictions, glass and other materials that reflect sound, background/road noise.

On the up side, the size and shape of the listening area is a known constant and you know exactly where the listeners will be seated and where the speakers will be located.

Lahti says the woofers that reproduce lower frequencies are the biggest challenge. They are large, heavy and ideally should be located at the corners in a sealed enclosure to be effective.

“So we place them in the doors with special attention during design to make sure they are rigid and . . . . there is nothing loose to rattle in the door assembly.”

Once you have determined the size and location of the speakers the phasing is addressed: ensuring the sound reaches front and rear listeners at the same time. This is a complicated tuning process involving dozens of settings in the hardware that can even change depending on whether the interior is cloth or leather.

The process can take months to complete, all in the name of a better audio experience in the vehicle and, surprisingly, for a reasonable fee considering the development time, effort and technology in the package.

And it’s only growing. Other high-end manufacturers are investing in high-end audio systems in the hopes that we’ll be drawn in by much more than how a vehicle merely looks and drives.

New sounds, new words

DVD audio. Much has changed since CDs were introduced 23 or so years ago, including how much music information can be put onto one disk. A standard CD holds about 700 megabytes of information. A DVD holds many times that amount of music information which means greater music detail and the ability to have more than two (left and right) channels. Of course, the system must be able to take advantage of DVD audio.

Center channel. Most of the vocals come out of the center channel speaker(s), which has to be centrally located for the best effect. Placement is one of the most difficult parts of adding an aftermarket surround system to a vehicle.

Stereo: Sound recording and reproduction by more than one (mono) channel. In home systems “stereo” is considered to mean two channels, left and right. In the film and entertainment industry it is understood to include surround and center channels as well. Such multi-channel stereo is commonly referred to as “surround sound”.

Dolby Digital 5.1. The sound information contained in each of six channels is distinct and independent. These six channels are described as a “5.1-channel” system, because there are five channels carrying the full spectrum of sound plus one low-frequency subwoofer channel.

Richard Russell is a seasoned automobile journalist with a background in engineering. He’s also a feature writer with Wheelbase Communications. You can message him on the web at www.wheelbase.ws/mailbag.html. Wheelbase is a world-wide supplier of automobile news, reviews and features.