> Why decibels beat adjectives: "Refined," "hushed" and "serene" are the vaguest words in motoring journalism. A sound level meter replaces all of them with a number. But there's a crucial catch — the decibel scale is logarithmic, so a 3 dBA difference represents roughly twice the sound energy. Small-looking gaps are larger than they appear. > > Populate the leaderboard with your own measured results.
Replacing adjectives with numbers
Cabin refinement is one of the most consequential qualities in a car you'll spend hours in — and one of the most vaguely described. Reviews call cars "hushed," "serene" or "well-isolated" without any way to compare one claim against another.
A sound level meter solves this. Measured in dBA (A-weighted decibels, which approximate human hearing sensitivity), noise becomes directly comparable between cars, and the results are frequently surprising.
The logarithmic catch
This is the single most important thing to understand before reading any dBA comparison, and it's routinely misunderstood:
The decibel scale is logarithmic, not linear.
- +3 dBA ≈ double the sound energy
- +10 dBA ≈ perceived as roughly twice as loud to the human ear
So a car measuring 68 dBA at 70 mph against one measuring 65 dBA isn't "slightly noisier" — it's carrying roughly twice the sound energy. Differences that look trivial on paper are substantial in practice, and this is why we always publish the numbers with this explanation attached.
Our measurement protocol
| Element | Standard | |---|---| | Meter position | Fixed position at driver's ear height, consistently located | | Measurements | Idle (or EV stationary) · 50 mph · 70 mph · full-throttle acceleration | | Surface | Standard smooth asphalt — recorded, as surface dominates tyre noise | | Secondary surface | Coarse/chip-seal where available — the difference is often dramatic | | Conditions | Windows closed, climate on low fan, audio off | | Runs | Both directions, averaged, to cancel wind | | Recorded | Tyre specification, ambient wind, surface type |
Surface choice matters more than almost anything. The same car can measure several dBA apart on smooth asphalt versus coarse chip-seal. Any noise figure without a stated surface is close to meaningless — and comparing figures measured on different surfaces is invalid.
Our test conditions: [to be completed — date, surfaces used, ambient wind, tyre specification, meter model and position]
The running leaderboard
Populate with measured results. Ranked by 70 mph cabin noise.
| Rank | Vehicle | Idle | 50 mph | 70 mph | Surface | Tyres | |---|---|---|---|---|---|---| | 1 | [to be measured] | | | | | | | 2 | [to be measured] | | | | | | | 3 | [to be measured] | | | | | |
Vehicles from this project awaiting measurement:
| Vehicle | Expected characteristics | |---|---| | Bentley electric urban SUV | Likely class-leading — silence is the brand's core value | | Mercedes C-Class Electric | "472 miles of calm" — refinement is its entire pitch | | Tesla Model Y (Juniper) | Acoustic glass and double glazing added; Tesla claims ~20% reduction | | Hyundai Ioniq 9 | Reported as remarkably quiet even by EV standards | | Polestar 3 | Reported quieter than the Model Y on tyre noise | | Porsche Cayenne Electric | Serene when asked; deliberately vocal when not |
What the numbers typically reveal
1. EVs are quieter at idle and low speed — but not always at 70 mph. Removing the engine eliminates the dominant low-speed noise source. At motorway speed, however, tyre and wind noise dominate, and these are unaffected by the powertrain. Some EVs are actually worse than refined combustion cars at 70 mph, because engine noise previously masked tyre roar. Removing the mask reveals what was always there.
2. Tyre noise becomes the defining factor. At 70 mph, tyre choice frequently matters more than sound insulation. Wide, performance-compound tyres are noisy; narrower touring tyres are markedly quieter. This is the single most effective change an owner can make to cabin noise.
3. Glass specification is genuinely effective. Acoustic laminated glass and double glazing deliver measurable reductions — Tesla's Juniper update added both and claims roughly 20% less interior noise, which our Model Y review found genuinely noticeable.
4. Active noise cancellation works, within limits. Effective against low-frequency drone, less so against the higher-frequency tyre roar that dominates motorway noise.
Why this matters more than it seems
Fatigue. Sustained noise exposure is genuinely tiring. On a long journey, a quieter cabin means arriving less exhausted — a real safety and comfort benefit rather than a luxury.
Conversation and audio. A few dBA determines whether you can talk comfortably at motorway speed or find yourself raising your voice for three hours.
Perceived quality. Quietness reads as expensive and well-engineered. It's a substantial part of why luxury cars feel luxurious, as our Bentley first drive argued — silence enhances everything else.
EV expectations. Buyers expect electric cars to be quiet, and are disappointed when motorway tyre roar undermines that. Measured data manages expectations honestly, which serves buyers better than adjectives.
The bottom line
Refinement deserves measurement rather than adjectives, and a sound level meter provides it. The essential caveat is the logarithmic scale: a 3 dBA difference represents roughly double the sound energy, so gaps that look small are genuinely significant.
Expect EVs to dominate at idle and low speed, and expect the picture to level considerably at 70 mph, where tyre and wind noise take over regardless of powertrain. Expect tyre choice to matter more than almost any other single factor — which also makes it the most effective improvement available to an existing owner.
And always check the surface a figure was measured on. Without it, a decibel number tells you nothing at all.
- dBA measurement replaces vague adjectives — but the scale is logarithmic: +3 dBA is roughly double the sound energy
- EVs dominate at idle and low speed; at 70 mph, tyre and wind noise take over and the advantage narrows or disappears
- Removing engine noise can expose tyre roar that was previously masked, disappointing EV buyers expecting silence
- Tyre choice is the single most effective lever on motorway cabin noise — more than insulation, for most cars
- Any noise figure without a stated test surface is meaningless; coarse and smooth surfaces differ by several dBA
Key takeaways
- dBA measurement replaces vague adjectives — but the scale is logarithmic: +3 dBA is roughly double the sound energy
- EVs dominate at idle and low speed; at 70 mph, tyre and wind noise take over and the advantage narrows or disappears
- Removing engine noise can expose tyre roar that was previously masked, disappointing EV buyers expecting silence
- Tyre choice is the single most effective lever on motorway cabin noise — more than insulation, for most cars
- Any noise figure without a stated test surface is meaningless; coarse and smooth surfaces differ by several dBA
Sources & further reading
- Acoustic measurement principles
- manufacturer NVH specifications
- True Motion Auto reviews (this project). *Populate leaderboard with measured results before publishing. Verified July 2026.*
Figures, prices and policy details were current at the last-updated date above. Automotive pricing, incentives and regulations change frequently — verify time-sensitive details with the linked primary sources. Read our editorial policy and fact-checking standards.
