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The use of a PU mini probe array enables a car panel noise contribution
analysis to be carried out without the need to put damping foam in the
car interior to create anechoic conditions.
The implications are important on both the higher value and lower
overall costs of the total data acquisition effort.
First of all, it becomes feasible to test a car safely under real test
drive conditions on the road, driving on a track, flying high up in the
air, capturing all data in less than one hour!
Secondly, the structure of the car itself to be evaluated is no longer
affected by the mass load of the foam applied.
Thirdly, significant time savings are possible for the overall data
acquisition time, affecting positively both required number of man-hours
and development lead times.
The actual required measurement time of sound
intensity contribution of a panel is less than 30 seconds.
With a suitably sized PU mini probe array in place, and appropriate and
affordable multiplexing methods reducing the number of data acquisition
channels required, a measurement set up becomes feasible that offers
much more value at much lower total system costs.
Post-processing, reporting and visualisation of
the data is relatively straightforward.
Timesavings up to 75% as compared to using traditional p-p methods are
reported.
Relevant papers
To be presented by Faurecia at the SAE in
Traverse City, Michigan, US in May 2005.
Vehicle Acoustic
Synthesis Method: improving acquisition time by using p-u probes (pdf)
05NVC-268
Jean-François Rondeau, Arnaud Duval, Guillaume Deshayes, Mathieu
Lassalas, FAURECIA
Hans-Elias de Bree, Microflown Technologies
Séebastien Chaigne, Renault
In order to reach OEMs acoustic treatment targets (improving performance
while minimizing the weight and cost impact), we have developed an
original hybrid approach called "Vehicle Acoustic synthesis method"[1]
to simulate - and therefore to optimize - noise treatments for both
insulation and absorption, and to calculate the resulting Sound Pressure
Level (SPL) at ear points for the middle and high frequency range.
To calculate the SPL, we identify equivalent volume velocity sources
from intensity measurements, and combine them to acoustic transfer
functions (panel/ear) measured or computed with ray tracing codes using
the reciprocity principle.
Compared to our first approach [1], this paper shows a new measurement
technique using pressure-particle velocity probes [2]. This technique
allows to reduce acquisition time by a factor four, and makes therefore
possible a synthesis method on a complete car within two weeks.
Paper Head Acoustics presented at the SAE in Traverse City, Michigan,
US in May 2005
Application of a New Window Technique for Panel Noise Contribution
Analysis
O. Wolff and R. Sottek
HEAD acoustics GmbH, Ebertstraße 30a, 52134 Herzogenrath, Germany
When designing the interior noise of a vehicle, it is often interesting
to know the noise contributions from single surface areas to the total
interior noise. The conventional "window method", sometimes also called
"subtractive procedure", requires the partial or full encapsulation of
the passenger compartment with a proper sound insulation package. This
vehicle condition serves as a reference. The sound level of the
reference condition is related to the measured sound level for sound
insulation packages where insulation material has been selectively
removed from the individual surfaces of interest ("windows"). The level
difference is used as a measure for the acoustical surface contribution
to the total sound level.
Unfortunately, test drives on roads are difficult to realise due to
safety reasons. The weight of the sound insulation package alters the
structure of the vehicle and also the absorption behaviour of the cabin.
Additionally, the preparation of the sound insulation package is
generally time-consuming and expensive.
However, HEAD acoustics has developed a new procedure, the binaural
panel noise contribution analysis. By using a special sensor array which
is applied to the surface under investigation, it is possible to perform
measurements while driving on the road. Vehicle structure and absorption
behaviour are not changed by the array. In addition to significant time-
and cost-saving benefits, this new procedure offers a wide range of
analysis possibilities. Room acoustics is taken into account and enables
users to listen binaurally to the noise contributions of individual
surface areas. The described procedure has been successfully tested on
several vehicles. |
Microflown Sound Pressure & Particle Velocity Sensors