Noise Reduction with QuietRide Sound Shield

QuietRide

This prototype QuietRide Sound Shield, made from canvas bonded to sound-dampening sheet vinyl stretched over a folding stainless tube framework, reduces passengers’ exposure to outboard noise levels at cruising speeds to below the OSHA-hearing-damage threshold of 85 dBA.

There are historically sound reasons to pay attention to new boat design ideas from the offices of C. Raymond Hunt Associates (doing business as Ray Hunt Design) in New Bedford, Massachusetts. Around 1960 the soft-spoken genius for whom the firm is named revolutionized high-speed powerboat design by insisting on running-surface deadrise angles between 24° and 20°, a characteristic that defines nearly all fast powerboats to this day. That’s why when company president Winn Willard wrote to me about his plans to reduce the noise from conventional outboard motors, I swung by the office to hear the details.

Out of necessity and convention, naval architecture in 2024 is pursued by offices full of finite element analysis experts and digital draftsmen refining miles of pipe and wiring schematics. Today’s Ray Hunt Design office has no shortage of degreed engineers and naval architects fine-tuning designs for high-end custom motoryachts, the latest production models from renowned American builder Grady-White, among others, and a steady flow of commercial and military boat designs for clients around the globe. That stuff has been their bread and butter for decades, though Willard and Principal Designer Peter Boyce observed that the market for new custom motoryachts built in the United States is very soft right now, having to compete with European and Far Eastern superyacht builders.

Willard has been thinking a lot about the scale of boats in recent years. “The whole superyacht world has exploded,” he said. “We used to look back on the 1920s and ’30s as the golden age of yachting, where we thought yachtsmen had big yachts.” Now yachts are really big, but their owners “are less yachtsmen than owners of floating palaces.”

With that challenge in mind, the Ray Hunt Design team is working on multiple aesthetic and technical variations and innovations to tempt buyers who are serious about boating, not just boat ownership, with some new quintessentially American yachts.

But it’s easy to get distracted by the big boats, and I was there to talk about the QuietRide Sound Shield, a design innovation at the other end of the yacht size spectrum and market. No surprise that Ray Hunt had already staked out significant credibility there with his design of the original unsinkable 13 (4m) Boston Whaler outboard skiff.

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Comparison of noise exposure from common activities and outboard motors

“He was an observer. He understood how boats worked and then could make a leap forward,” said Willard. In 1960, when Dick Fisher approached Hunt about designing a production sailboat to build using a new foam-cored-production process, the designer intuitively saw an opportunity and pushed him to the now ubiquitous, eminently stable outboard boat that launched the Boston Whaler brand and many imitators. It’s a good reminder that while Hunt’s credits include the gorgeous Concordia yawls, the America’s Cup 12-Meter Easterner, and a series of champion 5.5-Meter racing sloops, he was always interested in simple small boats and ways to make them more useful for recreation and commercial applications.

On one trip that brought Hunt into the office from his farm in New Hampshire, “he had sketches for his idea of an inflatable aft cabin that could attach to the transom of a 20 (6.1m) sailboat. When you’d sail to an anchorage, you’d anchor the boat and inflate the aft cabin, which would have a couple of bunks in it,” Willard said. “Ray was not constrained. He was always fiddling around with ideas and concepts…. QuietRide is in the Ray Hunt tradition of an idea that we think the industry needs. I knew for a long time how noisy outboards can be, and I said, ‘What the heck can we do about this?’”

The Need for Quiet

Opportunity to pursue the idea came with the declining demand for independent naval architects as many builders, especially those in Europe and Asia, brought design in-house. The Hunt team asked, “What as a design firm can we do or make or conceive of that makes us more profitable by making a product that isn’t on paper?” recalled Craig Emrick, QuietRide’s business partner. “If you’ve perfected the ride, what subcomponents can you look to?”

An answer was Willard’s longstanding concerns about noise on outboard boats. He remembered buying a Hunt-designed 30-footer (9.1m) with a pair of 350-hp (261-kW) Yamaha outboards. “We had this 50-odd-mph boat, but everywhere you went it was noisy as hell, and my wife said, ‘I want my sailboat back!’” If you went across the bay and anchored, it was quiet once you got there, Willard said, “but it was no fun to just go for a boat ride for a couple of hours—you can’t talk to each other.”

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Winn Willard’s test boat under way. Note that the soft shield is affixed to the transom and swim platforms surrounding the engine’s passenger-facing surfaces but leaves the back wide open.

It’s not getting better with newer models. He cited one recent large outboard model with a windshield and hardtop combination that traps the sound of the outboards in a resonating chamber. “It was 90 to 95 dBA at the helm, and this boat is going to cost $1.5 million. Would you buy that?”

The persistence of the trend prompted him to look more critically at the inconsistency of consumer expectations for inboard- and outboard-powered vessels. “If we designed a 30 inboard that had the same noise level as the outboard, people wouldn’t buy it, but they buy thousands of these outboard boats and just accept that they’re noisy,” Willard said.

The next step was to assess the decibel levels boat operators and passengers are exposed to. He knew that the maximum acceptable level in a Hunt-designed inboard was 75 dBA. But testing revealed that sound exposure on his own 20 outboard powered by a single 200-hp (149-kW) Yamaha was 105 dBA in the aft seat and 95 dBA at the helm. “You see pictures of lovely boats with people sitting in the backseats. I guarantee the sound levels next to those motors is somewhere in the vicinity of 100 dBA at cruise rpm,” he said. “OSHA [Occupational Safety and Health Administration] says the limit for sound exposure for an eight-hour day in the shop is 85 dBA.” Exposure to louder noise, or even 85 dBA for longer than 8 hours, can start to damage hearing. In loud workplaces employees must wear ear protection, but on recreational boats, there’s no such requirement.

Emrick noted that sound exposure increases logarithmically in relation to dBA measurements, doubling between 85 dBA and 95 dBA and again between 95 dBA and 105 dBA. That spans the typical sound range of a single outboard, with the lowest readings equivalent to a noisy restaurant or a handheld drill and the highest equivalent to that of a lawn mower, jackhammer, or rock concert. Exposure time to cause hearing damage contracts rapidly from 8 hours at 85 dBA to about 4 minutes at 105 dBA.

“It’s not to say if you’re exposed for 15 minutes, you’ll be deaf,” Emrick said. “But if you go on a two-hour trip, that’s a sizable exposure to the sound at cruise speed.”

“I’ve got tinnitus from exposure to outboards, saws, cars, lawnmowers…. I live with it,” Willard said. “But knowing this, I wouldn’t take my grandkids out and let them sit in the backseat of the boat.”

For a designer, placing those aft seats right next to the outboards is difficult to avoid, especially on smaller boats, where every square foot counts. It’s particularly challenging with an outboard well, where the engine intrudes on the cockpit space. It’s a little better on models with outboard brackets aft of the transom, but high noise levels remain a hazard across the full spectrum of modern outboard boats. Sound behaves like all energy and dissipates according to the inverse square law; the farther you are from the source, the lower the sound level. “Makes one wonder if that’s the reason bowriders are so popular,” Willard said.

While it’s difficult to get noise data from builders, Willard and Emrick looked to some historical data from on-water testing conducted by Boating Magazine of 40 randomly selected models between 17 and 44 (5.2m and 13.4m). About 63% of the boats yielded noise levels exceeding 85 dBA, and those measurements were taken only at the helm. Just 6% fell below the 75-dBA maximum Hunt designers adhere to for inboard vessels.

QuietRide’s Evolution

Having verified the need to reduce outboard noise, Willard set about designing a solution, starting with the source—the internal-combustion powerhead.

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A rigid QuietRide cowling fitted with grabrails.

“For the first tests I had a 15 [4.6m] RIB with a 40-hp [30-kW] motor,” Willard said. Using scraps of sound-dampening material from Soundown (Salem, Massachusetts), he shaped the acoustic insulating foam to fit tightly to the fiber­glass outboard cover, leaving a hole for air intake. The tidy option mimicked the type of rigid sound-dampening coverings common on marine generators. “It did nothing,” Willard said. “There were so many surfaces left exposed on the motor to radiate noise going all the way down into the water and then exciting the transom” that any sound-dampening effect was imperceptible.

Disappointed, he called Joe Smullin, a consulting engineer at Soundown affiliate J&A Enterprises, to confess and troubleshoot the failure. “Joe said, ‘What you need to do is build a barrier between you and the noise,’” Willard recalled.

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Rigid cowling doubling as a fishing platform fitted with rails and rod holders.

So the next iteration was more like a wall attached to the boat. This barrier had to accommodate the full volume of the outboard and not impede its ability to turn or tilt up, so the design would have to be much larger than the original. Ted Willard, Winn’s son and a designer at Hunt, said they also realized that the shield didn’t have to completely surround the outboard. They could leave the back wide open because, as Ted noted, “the sound can’t chase you.”

Sailors will recognize that Willard’s second attempt was inspired by the form of a classic canvas spray dodger that’s open aft and folds forward and out of the way when not needed.

“The covers we’ve played with so far are flexible heavy vinyl stretched over a metal frame.” Willard said. “We knew that we needed mass to stop energy—that’s just physics—but also the way the vinyl is just draped over the pipe frame allows [it] to move and absorb some more of the vibrations.”

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Soft low-profile folding shield.

They tried different weights and types of materials from Soundown and saw noise reductions in the 40% to 50% range. These results prompted a patent search. Finding nothing like it already in existence, Willard applied for and was granted a patent for boat-mounted acoustic covers. Next they asked Soundown to laminate some Sunbrella cloth to the vinyl to improve aesthetics and to build more prototypes for a range of motor and hull configurations.

In its simplest form, Willard said the material can be stitched on a commercial sewing machine. Similarly, the frame can be bent and assembled from the standard stainless pipe for dodgers and biminis. With a little practice he was able to have a local canvas shop build several prototypes. Hunt designers have also sketched out more complex applications, including wide shields for multiple outboards, molded shields with built-in grabrails or casting platforms, and automated deployment and retraction systems for folding shields.

Whatever form it might take at either end of the growing outboard market, the noise reduction results are going to be what drives interest in the shield technology. Going back to those original test figures of 95 dBA and 105 dBA, “with the cover on, we are able to get both those numbers down,” Ted said. The on-water testing indicates the helm station was 50% quieter at 75 dBA, while the seats at the transom improved by 40% to 85 dBA.

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Target noise levels on 20′ boat with and without sound shield.

The Market for QuietRide

Those are good initial results, but Willard stressed that there’s more work to do to refine the look and function of QuietRide options, including model-specific shields for a range of production boats. Because Ray Hunt Design is not a manufacturing company, it will be up to individual builders or an aftermarket components manufacturer to take it to market.

While they haven’t pitched it hard to any builders, they have surveyed boat dealers to gauge whether they get complaints from customers about outboard noise. “Most of the dealers answered, ‘Sometimes. It depends on the buyers,’” Willard said. “But they said they’d like to have an answer for those who object.”

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Comparative testing with and without QuietRide

Trends like the slower turning diesel outboards, which run quieter than most gasoline models, and electric propulsion are changing expectations for noise even as the outboard segment grows. Like a dodger or a bimini, if a sound shield were an option from the builder, it seems that buyers will bite. Emrick projects that the added expense would likely have to stay below 5% of the boat’s full purchase price. “There have got to be builders out there who are more forward-thinking or want to innovate,” he said.

Willard pointed to young boaters or the parents of young children as buyers likely to search out quieter options, especially if they were aware of the risks from exposure to standard outboard noise. He also suggested that commercial operators or agency and law enforcement buyers who must satisfy specified noise exposure rules could benefit from the QuietRide. Those sound exposure thresholds aren’t always about hearing protection; they’re also driven by the need for situational awareness and effectiveness. “The noise of the motor can affect the ability to do the job on the water,” Willard said.

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The soft shield needn’t be much larger than the outboard it houses. It must accommodate the full steering articulation of the engine in operation but can be folded forward when the engine is tilted up.

Whether it’s for work or pleasure, time on the water is more likely than ever to be powered by an outboard motor or two or three. The alarmingly high noise levels passengers and vessel operators are exposed to are already a problem, even if most of us aren’t aware of it. Builders and designers should take some comfort in knowing there is a technological solution that’s simpler than complete repowering with an electric- or inboard-propulsion system. Those of us on the water welcome any measure to make the experience of boating more pleasing. 

About the Author: Aaron Porter is editor of Professional BoatBuilder.