Reducing Cabin Noise A Major Focus In Developing All-New Mazda CX-5 – Insights

The early generation of SkyActiv-equipped Mazda cars, including the previous generation Mazda CX-5, were noted for their superior handling, youthful looks and premium looking interior. However they do have one weakness – cabin noise, a criticism that’s often levelled on Mazda cars.

In their pursuit of lightweight construction, which is central to Mazda’s SkyActiv philosophy, Mazda engineers were very selective in their use of sound insulation materials.

In markets like Malaysia, where enforcement of speed limits is lax and our wide network of highways mean that our average driving speeds is a lot higher than many other countries, the noisy cabin of Mazda cars when driven above 130 km/h is a common complaint.

Those undecided on the all-new CX-5 will be pleased to know that cabin noise was singled out as one of the key areas of improvement for Mazda’s latest mid-size SUV.

Minoru Takata, Program Manager for the all-new CX-5 explained that adding insulation materials to muffle out noise, a typical approach used by many car makers, just won’t do for Mazda as insulation materials add weight, which would in turn compromise not just fuel economy, but also the ‘Jinba Ittai’ oneness between car and driver driving feel that Mazda strives so hard to achieve on all its cars.

In order to reduce cabin noise without taking the easy way of simply adding insulation materials, Mazda had to go challenge itself further.

“We minimized the increase of weight (from having to add insulation materials) by analysing the root cause of the noise,” explained Takata, at this morning’s launch of the all-new Mazda CX-5.

Reducing the noise would require a combination of solutions – changing the materials used or adjusting a component’s thickness to minimize resonance effect, adjusting the panel gaps and improving aerodynamic properties of specific exterior components so wind flows smoother around the car.

Takata explained that cabin noise can be grouped into three types, each with their own characteristics and frequency range – road noise dominate in lower frequencies and they occur when the vehicle is driven over rougher tarmac, wind noise are higher frequencies and they only occur at higher speeds, likewise for tyre noise.

By employing model-based development, the industry buzzword for complex mathematical modelling to do highly detailed computer simulation and verification – tasks that would either not be possible or requiring very expensive physical prototypes and time consuming data gathering – the development team was able to virtually determine and measure noise levels at different parts of the car’s cabin very early on in the project.

This allowed the team more time to develop countermeasures for it. One notable change from the previous model was the structure of the roof and material of the roof lining. Some mechanical components have also been modified to avoid creating resonance with other moving components. Elsewhere, panel gaps and seals around the windows and door are tightened, which required similar improvements in production processes, to reduce wind noise. Door mirror designs also had to be tweaked.  

Takata adds that at speeds of 100 km/h, conversations inside the cabin of the all-new CX-5 are now approximately 10 percent clearer than before. When driving over rougher tarmac, cabin noise is now 1.3 dB lower than before, which is significant enough because one needs to remember that the dB scale is logarithmic and not linear. A 3dB increase in noise is equivalent to doubling the sound energy. In simple terms, a reduction of 1 dB represents approximately 30 percent reduction in sound energy, or 7 percent reduction in perceived loudness.  

Prices for the all-new CX-5 starts from RM134,205 (without insurance) for the base model 2.0G GL variant while the higher specifications 2.5G GLS petrol and 2.2D GLS diesel, ranges between RM160,596 and RM174,779 without insurance.

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