Quieter Cabin Through Reduction in Uncontrolled …
309
Table 2 Air leakage test values and in cabin noise level for different segment vehicles with air
leakage improvement actions
After implementation of improvement actions
Vehicle
Test cabin pressure
(kPa)
Leak rate
In cabin noise level
(db)
EBHS (cm 2 ) Flow rate (CFM)
Car (mid
segment)
150
50
180
65
SUV
(monocoque)
150
42
150
64
SUV (body on
chassis)
150
44
160
66
3.3 Cabin Acoustic Measurement
To capture the acoustic improvement, in cabin noise measurement has been carried
out in both conditions that is pre improvement and post improvement vehicles.
Measurements are carried out with controlled parameters such as maximum speed
of vehicle was 60 kmph, position of dB meter kept same in all segment of vehicle
that is near co-drivers right shoulder, AC was in off condition, recirculation mode
was ON, all window glasses were up, all vehicles tested on the same track with same
surrounding condition.
4 Conclusion
Air leakage is one of the key parameters contributing to higher in cabin noise levels.
The correlation can be established between air leakage rate and in cabin noise level.
In cabin noise level is directly proportional to air leakage rate, higher the leakage
more the in cabin dB level. Individual vehicle noise level improvement can be seen
with the help of values mentioned in Tables 1 and 2. It shows that in cabin noise
level reduced to on an around 65 dB which is rational value for vehicle cabin noise.
Figure 7 is the combo chart which depicts all three segments with pre and post values
of leakage rate and dB level.
Next level of study is planned with in cabin AI (Articulation Index) measurement
to figure out direct benefit to passengers and improvement in cabin comfort.