Car and Driver has revolutionized its approach to evaluating vehicle acoustics by integrating a novel measurement unit called "sones." Historically, the publication relied on A-weighted decibels (dBA) to quantify interior sound levels. While dBA provided a standard, its logarithmic nature and filtering of low-frequency sounds often made it challenging for readers to intuitively grasp the true perceived loudness. Recognizing this limitation, the team sought a more transparent and perceptually aligned metric.
To enhance the accuracy and comprehensibility of their sound evaluations, Car and Driver now employs a sophisticated Brüel & Kjær 2250-L sound-level meter at a dedicated Michigan test site. This ensures consistency across all vehicle tests, as variations in road surfaces can significantly impact sound readings. Standardized measurements are meticulously collected at idle, during a steady 70 mph cruise, and under wide-open throttle acceleration. The introduction of sones offers a linear scale that directly correlates with how humans perceive loudness, a crucial distinction from the A-weighted decibel scale which merely mimics this perception. This innovative approach involved a jury to fine-tune the sones scale, making it a more user-friendly indicator for consumers.
The benefits of using sones are evident in comparative analyses; for instance, the Ford Mustang GTD's idle registered 10 sones, indicating it's 43 percent louder than the Chevrolet Corvette ZR1's 7 sones. Similarly, a Nissan Armada Pro-4X at 70 mph, at 19 sones, proved 14 percent quieter than a Chevrolet Suburban High Country, which recorded 22 sones. While A-weighted decibels will still be reported for wide-open throttle scenarios, the adoption of sones, with its clearer representation of loudness (where 40 decibels at 1000 hertz equates to one sone), provides invaluable insights into vehicle quietness. For example, the Genesis Electrified GV70, at 18 sones and 64 decibels at 70 mph, stands out as exceptionally quiet, particularly when contrasted with the much louder Porsche 911 GT3 Touring, which clocks in at 44 sones and 79 decibels at the same speed, underscoring the significant impact of sound on the driving experience.
This pioneering shift in sound measurement by Car and Driver not only refines the precision of vehicle evaluations but also empowers consumers with a more accessible understanding of automotive acoustics. By emphasizing perceived loudness through sones, the publication fosters a deeper appreciation for engineering excellence in noise reduction and vehicle comfort, promoting innovation that truly resonates with the human experience.