This two-part experiment was designed to measure and analyse the in-cabin noise levels of the Mahindra BE6 under two different operating conditions—while cruising at various speeds (Experiment 2a) and with different air conditioning blower speeds (Experiment 2b)
BHPian adithya.m.bhat recently shared this with other enthusiasts:
Experiment 2: Cabin Acoustic Behaviour
This two-part experiment was designed to measure and analyse the in-cabin noise levels of the Mahindra BE6 under two different operating conditions—while cruising at various speeds (Experiment 2a) and with different air conditioning blower speeds (Experiment 2b). The aim was to understand how external (road/wind) and internal (blower fan) noise sources contribute to the overall cabin sound profile of the vehicle.
Experiment 2a: The Cabin Noise at Different Vehicle Speeds
Theory: This experiment was inspired by a Team-BHP thread (which I unfortunately can’t find anymore) where multiple owners shared the in-cabin noise levels at various cruising speeds. I found that idea extremely relevant—especially in the context of EVs. As we know, EVs are inherently quieter than ICE vehicles since there’s no internal combustion process. Instead, chemical energy from the battery is converted to electrical energy and then to mechanical energy via electric motors—all of which operate almost silently. However, with the absence of engine noise, road and wind noise becomes more noticeable. To counter this, manufacturers have introduced enhanced insulation within windows and tyres, and automotive acoustic engineers have added technologies like active noise cancellation, sound-deadening materials, and improved body seals. The result? Modern EVs, including the BE6, offer impressively quiet cabins.
With this understanding—and the BE6 at my disposal—I decided to run my own test.
Objective: To measure cabin noise levels at different constant speeds and evaluate the acoustic insulation quality of the Mahindra BE6.
Methodology: To run the experiment, I needed a consistent, open road surface (preferably asphalt/concrete) with minimal traffic. Fortunately, the Bengaluru–Chennai Expressway, which passes close to home and is yet to be fully commissioned, served the purpose perfectly. It connects a few villages currently, has minimal traffic, and has non-operational toll booths. Best of all, the speed limit is 120 km/h, giving me a wide range of speed to test.
For noise measurement, I selected a well-rated ‘Sound Meter’ app with a 4.4 star review and over 1 crore downloads.
What I liked about this app is that it provides a graphical view of the sound level profile in decibels. It also shows the minimum, maximum, and average sound levels, for a duration, and the duration can be reset with a tap.
To ensure consistent and uncontaminated readings, several conditions were carefully maintained throughout the test. The windows were fully rolled up, music was turned off, and both the interior and exterior ambient sounds from the SonicSuite were disabled. The air conditioning was set to 22°C with the blower speed at level 1, and seat ventilation was turned off to eliminate any airflow noise. (VNC+ was kept to high throughout the 2a and 2b tests.)
The mobile phone used for recording was placed securely on the flat, aircraft-style gear selector lever, which helped avoid any unwanted sounds from contact with hands or surfaces. To further reduce interference, the AC blower direction was adjusted so that air was directed toward the occupants’ faces and away from the phone’s microphone.
Ambient temperature during the test: 27°C
Odometer reading: 3,697 km
Drive mode: Default
Battery SoC at start: 66%
Observations: Cruise control was used to maintain stable speeds throughout the test. Speeds were set incrementally from 50 km/h to 120 km/h, increasing in steps of 10 km/h. At each speed, the sound meter app was reset, allowed to stabilize, and the noise level was recorded. To improve accuracy and account for external variables, two readings were taken at each speed—one during the onward journey and another on the return leg.
Snap of Driver Information Display at beginning of return leg:
For the 120 km/h test, the reading was recorded at 119 km/h to avoid interference from the mandatory over-speed chime.
To help interpret the decibel values in a more relatable way, the app provides a reference legend mapping sound levels to common real-world scenarios. A screenshot of this scale is included below:
With this method put in force, the following data was recorded and compiled into an Excel sheet for clarity:
Experiment 2b: Cabin Noise from Different AC Blower Speeds
Theory: While Experiment 2a focused on noise generated by external factors like road and wind, the next logical step was to isolate and analyze in-cabin noise generated by internal systems—specifically, the HVAC blower fan. As blower speed increases, the fan generates more airflow and consequently more audible noise, which can become a significant contributor to overall cabin sound, especially in a stationary EV where there’s no engine hum to mask it.
Objective: To measure the increase in cabin noise at various blower speed settings using the same app and test method, but in a stationary vehicle.
Methodology: The same ‘Sound Meter’ app and phone placement (on the flat aircraft-style gear selector) were used to maintain consistency with the previous test. Since vehicle motion was not required, measurements were taken at two quiet locations: one at a parking bay near the start of the Bengaluru–Chennai Expressway, and the second near the toll plaza on the return. All other environmental variables (windows up, music off, SonicSuite off) remained unchanged.
Observations: The following data was recorded at each blower setting:
Combined Results: The cruising test revealed a smooth and predictable increase in cabin noise, rising from 51 dB at 50 km/h to 61.5 dB at 119 km/h—consistent with the expected rise in wind and road noise at higher speeds. In contrast, the blower test highlighted the influence of internal airflow on cabin acoustics. Starting from a near-silent 30 dB at the ‘Off’ setting, cabin noise increased steadily, reaching 61.8 dB at blower speed 8—remarkably close to the sound level observed while cruising at 119 km/h. An interesting observation is that up to blower speed 4 (around 49 dB), the cabin remains quieter than—or comparable to—cruising at 60–70 km/h. This correlation is clearly illustrated in the comparative plot below, where both cruising and blower noise levels are displayed on a common decibel scale for easy visual comparison:
It’s important to mention that these two results—external driving noise and internal blower noise—should not be directly added together. For instance, while cruising at 80 km/h (~57 dB) with the blower set to level 4 (~49 dB), the overall cabin sound may rise perceptibly, but not linearly. Since decibel levels are logarithmic, the actual combined impact would depend on how the two sound sources interact acoustically within the cabin environment.
Additionally, the BE6 offers a VNC+ (Vehicle Noise Compensation) feature within the audio settings, which claims to provide active noise cancellation when media is being played.
To evaluate its impact, a supplementary test was conducted using the same sound meter app, this time at a constant cruising speed of 100 km/h with a fixed audio volume. The VNC+ feature offers four modes: Off, Low, Mid, and High. For this experiment, only the ‘Off’ and ‘High’ settings were tested. A consistent music track was played from the beginning up to the 20-second mark for both tests, with all other variables held constant. Surprisingly, the average noise level was exactly the same—64 dB—for both settings. Because there was no noticeable difference, I didn’t explore the other modes further. It’s possible that I haven’t fully understood how VNC+ works yet, or maybe the feature is meant to adjust for different driving conditions that weren’t part of this test. It could also be something that gets activated more effectively through a future software update. Either way, it’s another one of those quietly included features that leaves room for pleasant surprises down the line.
Combined Conclusions: These two experiments together provide a well-rounded view of the BE6’s cabin acoustic behaviour, both in motion and at rest. The cruising test revealed a smooth and predictable increase in cabin noise, rising from 51 dB at 50 km/h to 61.5 dB at 119 km/h. This progression is smooth and indicates that Mahindra has implemented effective noise isolation, making the BE6 genuinely quiet even at high speeds. For comparison, my previous vehicle—a Baleno RS—would exceed 75 dB at similar speeds. While the two belong to different segments, the BE6 represents a clear step up in refinement for me, particularly when it comes to long-distance cruising comfort.
In the blower speed tests, the results highlight how internal airflow can influence perceived cabin noise. Starting from a whisper-quiet 30 dB with the blower off, noise levels gradually climbed to 61.8 dB at the highest setting (speed 8)—a level on par with cruising at nearly 120 km/h. Blower speeds up to level 4 remained acoustically subtle, but levels 6 and above introduced noticeably louder airflow, which may matter to those using the vehicle as a mobile workspace or those particularly sensitive to noise. A particularly thoughtful and user-centric feature deserves mention here: the BE6 automatically lowers the HVAC blower speed during incoming calls. This small but impactful touch helps improve voice clarity by minimizing background airflow noise, underscoring the vehicle’s quiet refinement and attention to user experience. Interestingly, this isn’t a feature Mahindra actively advertises. In fact, it’s one of several hidden gems that have pleasantly surprised me during my time with the BE6.
In essence, whether stationary or at speed, the BE6 provides a cabin environment that’s calm, acoustically insulated, and intelligently engineered. It’s not just an EV in terms of drivetrain—but in its quiet, focused, and refined user experience as well.
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