Using innovative aeroacoustics testing tools to reduce the time it takes to pinpoint noise sources by 94 percent

Exceeding expectations

Three key factors that motorists demand from vehicles are energy efficiency, comfort and speed.

Wind tunnel testing is crucial to satisfying these demands. Aerodynamic performance not only affects speed but also energy consumption – the more streamlined a vehicle is, the less energy or fuel is required to overcome air resistance.

Although ergonomically designed seats and air conditioning are important, noise management is also significant in ensuring comfort. Testing and improving aeroacoustics performance is another vital aspect of wind tunnel use.

For Honda, it is about much more than meeting the minimum standards. “Honda’s main goal in everything we do and every product we make is to ensure our customers’ expectations are exceeded in every way,” says Mike Unger, full scale wind tunnel unit lead. “Customer expectations drive almost everything that we do.

”To help them achieve this goal, Honda uses microphone arrays connected with Simcenter™ SCADAS™ hardware and Simcenter Testlab™ software, part of the Siemens Xcelerator business platform of software, hardware and services, to conduct aeroacoustics testing to identify and remedy areas of concern. These solutions help Honda reduce the time it takes to
pinpoint noise sources from four hours to 15 minutes, a reduction of 94 percent.

Wind tunnels have their limitations

“In the past, we rented wind tunnels all around the world,” says Unger. “We had associates traveling two weeks of every month to various wind tunnels across the globe, doing acoustics in one part of the world, aerodynamics in another and racing in yet another facility.”

Not only was it tough on the people, but shipping vehicles overseas was costly and time-consuming. They ended up with lots of dead time when vehicles were in transit and not being used for testing.

So it made sense to build their own wind tunnel facility in Ohio where they are based.

But Honda did not want to build just any wind tunnel. They wanted to build a state-of-the-art facility based on experiences they had working in other wind tunnels around the world.

The result was Honda Automotive Laboratories of Ohio (HALO).

The wind tunnel of the future

The main purpose of the new wind tunnel is to provide all the aerodynamics and aeroacoustics testing on everything from clay models to production cars. It supports Honda’s U.S.-based Auto Development Center as well as its North American auto production facilities with their wind noise, quality sampling and customer satisfaction activities.

“HALO is unique in terms of the scope of testing we can carry out,” says Unger. “We can test everything from a passenger car with a maximum speed of 100 miles per hour all the way up to an Indy car that does 190 miles per hour. We can assess the aerodynamics as well as the aeroacoustics across the same speed range.”

Unger says that the capabilities of HALO are unmatched across the world, “There’s not another wind tunnel that can go faster, is as quiet, has an array, a five belt, a wide belt and a traverse.”

HALO has been designed for maximum efficiency because wind tunnel time is so expensive. Sam McCrary, operations leader, explains, “From putting the car into the facility and getting the equipment going and running tests, everything is set up to be as easy and as quick as possible. So not only are we eliminating all the travel and shipping costs, but we’re also
getting as much value as we can from every minute of wind tunnel time.”

Quieter vehicles

Aeroacoustics testing has become even more important in the development of electric vehicles (EVs). With no internal combustion engine (ICE) masking sounds, wind and road noise are now much more noticeable.

McCrary explains that aeroacoustics is important because it directly influences customer perception of vehicle quality and comfort: “They don’t like to hear abnormal noises. They want that secure, silent feeling of a luxury vehicle.”

As vehicles have evolved, it has become more complicated to diagnose the sources of sounds so limiting background noise of the wind tunnel is critical for aeroacoustics testing. “You want that threshold to be as low as possible,” says McCrary. “We applied a lot of different countermeasures such as pile fabric to help reduce the reflections off the collector. Our control room window is angled so the reflections don’t point directly onto the vehicle.”

Integrated systems are also key to successful, efficient testing. When data acquisition hardware, software and tunnel system software are all used on different systems, that can make it challenging for engineers to summarize results. “It was essential for us to build a facility where the aeroacoustics testing was combined into one system,” notes McCrary.

Pinpointing noise sources

To ensure this integration, HALO uses Simcenter SCADAS and microphone arrays combined with Simcenter Testlab for its aeroacoustics testing. To capture data, external and internal microphone arrays are used to connect to Simcenter SCADAS. This connects with Simcenter Testlab so the user can identify problems in almost real time. Engineers then carry out root-cause analysis to understand what’s creating the noise.

Pinpointing sources of noises is one of the biggest challenges vehicle manufacturers face. Antonello Bianco, HALO technical expert, explains, “We have four different beamforming arrays that capture information simultaneously. This allows for correlation and transfer path analysis to show us where we need to focus our investigation.”

Maxim Purvis, wind tunnel test engineer, gives the example of a windshield producing a whistling noise. “By using one of the coherence methods, referencing one of the inside microphones compared with the outside array, we’re able to pinpoint where the noise is coming from on the outside of the vehicle and where it’s funneling inside the car. Once you know exactly where the problem is, it can be fixed in a matter of minutes. Otherwise, you can spend hours guessing where it might be and trying lots of different solutions.”

“Previously with trial-and-error it used to take engineers three or four hours to identify where a noise was coming from,” says Unger. “Now we can do it in 15 minutes with extreme precision.”

"There used to be a lot of back and forth between the operator and the person taking acoustic data,” says McCrary. “There was constant communication between them, but this introduces lots of potential for human error.

“Integrating Simcenter Testlab with our wind tunnel control software has made a huge difference. Direct integration means we can write detailed test sequences with our wind tunnel control software and Simcenter Testlab automatically runs it as specified. There’s no chance of input errors and the whole process is much faster and more efficient.”

A new benchmark

With HALO in place, Honda is now well positioned to develop some of the most comfortable cars in the industry. The partnership with Siemens Digital Industries Software has delivered a world-leading facility in its scope and breadth. As vehicles continue to evolve and abnormal
noises become more noticeable, HALO engineers will be able to locate and eliminate them more efficiently and swiftly than at any other wind tunnel in the world.

“The Siemens team understood the testing process and what we wanted to achieve,” says McCrary. “The fact that Siemens has engineers with extensive experience in the area was important to us.”

"Honda has a long history working with Siemens,” says Unger. “We explained our requirements and they were able to deliver equipment that met our needs and expectations.”

“One of the great things about working with Siemens is their service and support,” adds Purvis. “They’ve been very helpful as they’re quick to respond whenever we have a problem.”

Having built such an impressive facility, Honda is now considering making it available to external customers. “As cars evolve and get even quieter, our ambient levels are so low that we’ll still be able to measure any noise coming off the car,” says Unger. “Couple that with the acoustic array and the efficiency and ease of acquiring data, we offer a skill set that doesn’t exist elsewhere in North America. Wind tunnels are used in a range of industries, not just
automotive, so we’re looking at how we can make HALO available to others.”

Honda and Siemens are working together to help pave the way for a future of quiet, comfortable travel.