16 / 10 / 2018

AN INTERIOR WHERE TRANQUILITY MEETS EXCITEMENT

Quietness is in the DNA of the ES — a quality that has been inherited by every subsequent generation.

But the latest seventh generation ES was conceived as a higher-segment vehicle.

Achieving a level of quiet suitable for such a classification was a true challenge that took three years of innovation, creativity, and patience.

Quiet, not soundless

There is something about the complete silence created in a soundproof space that is cut off from the outside, such as a radio or recording studio, that can be unnerving or even suffocating—not quite the relaxation one normally associates with quietness.

The same applies to the silence inside a car. Although a low level of noise is particularly important in a luxury model, where the driver expects to be able to enjoy music and conversations without difficulty, quietness should not be mistaken for a complete lack of sound. Creating a quiet atmosphere is actually about allowing sounds that are pleasing to the ear to flow freely through the car, while doing everything possible to suppress unpleasant noises. Such an audio environment is essential to the interior design of a car.

“Every generation of the ES has had a reputation for offering an impressive level of quietness,” says Hirotaka Tsuru, who designed the noise and vibration control and sound control of the new ES—the seventh-generation model. “Naturally, we considered a quiet cabin to be the most important feature when developing the latest model. The LS, as well as its higher-segment competitors, served as our benchmark for this project.

“Quietness is not a quality that can be improved by simply blocking more noise. For example, we developed a test model in which we greatly suppressed bandwidths at or around 1 kHz—the range that is most readily picked up by our ears. But doing so raised the air density inside the car, which caused ringing in the ears and even nausea—not relaxing at all.”

Noise source elimination, sound insulation, and noise absorption

Tsuru, of course, was erring on the side of caution—his job, after all, was to cut off driving noises that the driver and passengers may find unpleasant. “Quietness is in the ES’s DNA,” Tsuru says. To ensure that the new model properly inherited this quality, Tsuru divided his task into three phases.

First, he focused on eliminating noise sources. Early on during the development of noise and vibration control, Tsuru incorporated wind tunnel testing—more commonly employed in air resistance development—to pinpoint every source of wind noise. He tested the car under a number of different circumstances, making tiny adjustments in the position of the outer mirrors, wipers, and other car parts with each trial. With each source of wind noise he found, he worked to reduce the volume of airflow, even if it was just a few milliliters.

Next, Tsuru turned his focus to sound insulation as a way of reducing the noise entering the car. This phase involved cutting off passages through which noise could enter, through methods such as filling in openings in the floor and inner trunk lid or sealing them off with sheet metal. In the third phase, Tsuru focused on noise absorption. He applied absorbent to the suspension tower, fender, undercarriage, and other areas.

“Thanks to our use of wind tunnel testing, we were able to efficiently reduce the level of wind noise in very little time,” Tsuru says. “The advantage of using the Lexus wind tunnel is that it is a lab designed for testing low-noise levels, which means we can quantitatively measure the wind noise level while controlling for interior noise levels and interior noise sources.

“With regard to sound insulation, from the time we began to develop the new platform, we were already studying ways to reduce the number of openings and were considering covering the entire floor with silencers, which in previous models had only been placed on some parts of the floor. In other words, the new ES represents our effort to greatly improve the specifications of the car base itself.”

Through imagination, creativity, and meticulous engineering, Tsuru sought to take the ES car base to the next level and, in the process, produce an environment of comfortable quietness that skillfully filters out sounds that the driver may find unpleasant. However, achieving such an ambitious design was never going to be easy. Factors such as road conditions– which change moment to moment while driving– are always difficult to account for when designing a car. Although one cannot fully prepare for changes in external factors, failing to account for sounds at certain bandwidths may result in those sounds being even more perceptible than usual– in other words, an even noisier car.

“If you look at other modes of transportation, planes have a sound pressure level of 80 decibels,” Tsuru says. “In cars, that figure is usually between 60 and 70 decibels. Generally speaking, people find higher sound pressure levels to be more irritating to the ears.

However, despite the level being higher in planes, most people would not consider planes to be particularly noisy. When you’re in a car, though, the environment through which you travel constantly changes. Depending on the circumstances, you might find the ride to be noisy even if the sound pressure level is not that high. Changes

in the environment are most often caused by natural winds and changes in the road condition. In the end, we needed to incorporate these factors into the design as well, in order to produce a pleasing aural environment in which every type of sound– both good and bad– is precisely adjusted. It was a difficult process that required a lot of patience.”

An engine sound that embodies the thrill of an F SPORT with a 3.5-L V6 engine

In this way, Tsuru was able to dramatically upgrade the ES in terms of noise and vibration control and sound control. One new feature in particular deserves special mention: the Engine Sound Enhancement (ESE) incorporated in the car’s 3.5-liter V6 engine. Thanks to ESE, the F SPORT’s thrilling performance is matched with an equally dramatic engine sound.

“As the engine rotates faster, the primary, secondary, and tertiary ignition sound components are manipulated to create a linear and beautiful harmony of sound waves that is also dynamic and impactful,” Tsuru says. “As a result, we were able to establish the identity of the new ES through its engine sound. Essentially, the ESE produces sounds that are merged with the actual engine sound—which consists primarily of these ignition sound components– to create an auditory effect that crescendos smoothly and linearly.”

This means that dynamic sound effects are produced not only when starting the car or accelerating—such as when merging onto a highway–but also when shifting down gears via paddle shifters, such as on a winding road. In this way, the new ES provides drivers with a more sensory way of experiencing the joy of driving.

“The new ES is the first to incorporate F SPORT specifications,” Tsuru explains. “It has a V6 engine that allows for a much more powerful performance. We didn’t want to sacrifice the quietness that the ES is renowned for, nor did we want to prevent drivers from enjoying the engine sound that is part of the thrill of driving a sports car. This is why we created a sound design that allows for both.”