Characterization of the Automotive Interior Cabin Noise - Research Proposal Example

?RUNNING HEAD: INTERIOR CABIN NOISE Characterization of the Automotive Interior Cabin Noise: Interior Trim Acoustic Materials Characterization of the Automotive Interior Cabin Noise Refining the noise and vibrating features of private vehicles has been a headache for the automotive industry. They are working tirelessly to ensure that these noise and vibrating levels are kept to a minimum. The interior design of a vehicle is the major factor that determines the interior noise and vibrating levels whereby the interior design will either keep these levels to a minimum or accelerate the noise and vibrating levels. Consequently, interior trims such as the car-seats and roof covering play a very vital role in the observation of interior noise and vibrations specifically in relatively heightened frequencies (>400Hz). This therefore means that the automotive industry has had to focus on the redesigning the interior of this personal cars to make the cars as quiet as possible. The automotive industry has been compelled to enhance their interior trim products with better designs due to eco-friendly factors such as whether these products are recyclable, the fact that the noise and vibrating levels have the possibility of resulting to serious health issues and price of products. However, there is still a lot of research that need to be done in order to get a more profound understanding of the consequences of the interior trim design on the noise and vibrating levels. Once this improved and refined trim designs and concepts are recommended for the automotive industry, this need to enhance their interior trim products with better designs will become even more obligatory. Hence, this research paper is anticipated to deliver a practicable process which can estimate and optimize the interior cabin noise level for dissimilar interior trims and seating arrangement. In carrying out this research we first have to understand the effects of vehicle interior trims in minimizing interior cabin noise. In doing so, we will begin by establishing the noise characteristics. In establishing the noise characteristics of interior design, I will peg my research on a paper published by Jha and Priede which investigated the simplest mechanism of understanding how noise is generated in a car. This noise is majorly caused by the vibration of the cabin walls. While this research was carried out over 30 years ago the findings from this research are still applicable with the design and features of an ordinary modern day vehicle. Jha and Priede carried out experiments of internal noise spectra of a number of vehicles. The internal noise spectra of the vehicles were also done at contrasting speeds. The internal noise spectra was seen to elevate to an all-out level of 20 Hz and later decrease at a constant rate of averagely 25 Db per decade to a level exceeding 1 kHz. Although, the frequency at which the highest level of noise is experienced normally depends on the size of the car, the corresponding interior noise spectra for all personal vehicles as investigated by Jha and Priede are all alike. The rotation of the wheels are one of the major contributors of interior noise and vibrations whereby they result to noise peaks of about 20 Hz which in combination with various harmonics result to a lot of noise and vibrations within the car. The engine is also a major contributor of these noise and vibrations within the car whereby when an engine fires it produces harmonics of a low order that account for a frequency of about 100Hz. The second part of this research will be identifying the role of different trims in absorbing noise and vibrations produced within the cabin. The most commonly used trims are Acoustic Insulation materials. These materials that are applied in the reduction of noise and vibration levels within a personal car have the following mechanism; they first absorb the energy produced which is then transformed into heat energy. This transformed sound energy is reflected away from the vehicle. The acoustic insulation materials act as both absorbers and a reverberator. However these acoustic materials have some effects. First of all these acoustic insulation materials add a significant weight to the vehicle. This significant weight therefore has to be accounted for by the engineers and therefore the car has to be redesigned to be able to account for this weight. Secondly, another effect of acoustic materials such as fibreglass is that they are very delicate and can only withstand so much noise or vibration and hence get damaged easily. Furthermore acoustic materials such as mass layers are flammable and hence have the possibility of causing a fire. Another effect of this acoustic insulation material is the fact that this is an added expense to the car manufacturers. These acoustic materials used for insulation are quite expensive as they are used in ships and aeroplanes. This therefore is an added cost to the manufacturer (Zienkiewicz, 2007). The third part of this study will be aimed at finding out how we can predict interior cabin noise in mid-high frequency range >400 Hz.  In doing so we first have to look into an automotive high frequency (>400) interior noise measurement test data collection on a selected car. A recent study of a number of Isuzu Rodeos and Isuzu pick-up trucks were used in an experiment to measure the automotive high frequency (>400 Hz) interior noise. On each of the vehicles, they tested the vibrations that were being subjected on the acoustic materials and then they determined the frequencies. The recording of the vibration on the acoustic materials was done on both the roof lining and on the seats. For the Isuzu sedans he frequencies were seen to be significantly lower than that of the trucks whereby the sedans recorded harmonics of a low order that account for a frequency of about 150Hz while the pick up tracks recorded harmonics of a low order that account for a frequency of about 200Hz. This was mostly caused by the fact that the trucks had bigger wheels and therefore meant that they made longer rotations that led to a lot of noise and vibrations. Another reason was that the trucks have a relatively bigger engine capacity which therefore produces low order harmonics which translate into high frequencies (Koopman, 2006). CAE concept modelling of automotive interior trim for SEA simulation is a Hyper Mesh & Auto SEA2 software. It is being tested to be able to be used to reduce noise and vibration levels in vehicles. The CAE concept modelling of automotive interior trim for SEA simulation can be done to simulate a situation of a vehicle with noise levels of over 200 Hz. In doing this car manufacturers can find ways to completely cut off noise and sound vibrations that are of above 200 Hz unlike other methods. This technology can be used to determine the perfect places in the interior of the vehicle for example the roof lining of the vehicle or below the seats of the vehicle, for perfect reduction of noise and vibration reduction (Yashiro, 2007). This simulation has determined that the best material to reduce noise should be very light and therefore it would not affect the weight of the car at all and therefore it reduces the work for the manufacturer of accounting for the weight. The CAE concept modelling of automotive interior trim for SEA simulation is also very easy to use. It requires minimum knowledge to operate. It is also a safe product whereby it does not have any health related risks to the passengers. It is also not flammable and therefore ensures the safety of the passengers. However, CAE concept modelling of automotive interior trim is very expensive especially due to the fact that it is still a concept (Desment, 2007). The efforts put in its research and design in terms of resources and funds are enormous therefore obtaining these products for many manufacturers in the automotive industry will be expensive. In correlation of the test data for the Isuzu vehicles and the simulation results we discover that the noise level measurements that were done practically through physically testing the vehicles and recording in the test data were not as accurate as those that were done using the CAE concept modelling of automotive interior trim for SEA simulation. This is due to the fact that the in carrying out the test data experiment of the Isuzu vehicles issues like the wind speed the climatic condition and other foregone factors were not considered and hence the recordings were not as accurate. For the simulation, all factors are considered and calculations are made considering all this factors and hence the recordings and findings made are more precise (Sas, 2006). The experimental parameter study of the stage 5 for further correlations and tuning of the concept interior model involved further correlation between the test data and the simulation results in detail. It was done in order to determine how to improve the performance and accuracy of the simulation. It would facilitate the reinvention of the simulation for it to be able to acquire more profound and accurate results. It is also for the simulation to take in more real world conditions and be considered in the simulation to bring about more accurate findings. The interior model of the simulation was incorporated with a situation of more passengers and also added features whereby the passengers were listening to music in the vehicles and also other different situations within the vehicle that would affect the results of carrying out a noise level measurement experiment. There are different methods that have been developed to determine the internal noise and vibration levels and also the amount of sound energy absorbed by the material used to reduce these levels. Firstly there is the FEM-BEM (Finite and Boundary Elements) which is usually installed in the airspaces of the vehicle. This method is also limited in that it can only be used to measure noise levels that produce harmonics that result to frequencies of less than 200 Hz. Another method is SEA (Statistical Energy Analysis) which can be used to measure sound frequencies of above 200 Hz. It is also the one mostly applied in simulations. There has been the validation of the development of new trims that are more effective in the reduction of the noise and vibration levels in vehicles and therefore. These new trims are taking into account the disadvantages of the other older trims which were seen to be ineffective, heavy, sometimes flammable and also expensive. The new trims are light and also do not bring a difference in appearance of the interior look of the vehicle they are not flammable and also cheaper (Nefske, 1995). Prediction and verification of the new Futuris Proposed new concept interior trims whereby the trims were to be installed in the roof lining of the vehicle and below the seats this will ensure that vibration that emanates from the body of the car is completely neutralized. This concept is seen to be light and inconspicuous. This concept I believe will be very effective in the reduction of noise and vibration levels as it is easily installed in vehicles and that it captures all the vibrations levels that is produced (Petyt, 1999). References Koopmann, G. H. and Pollard, H. F. (2006). “ A joint acceptance function for enclosed spaces.” J. Sound and Vibration, 1980, 73(3), 429. 25 Zienkiewicz, O. C. (2007). “ The ?nite element method, 3rd edition.” (McGraw-Hill, Maidenhead).26 Petyt, M., Lea, J., and Koopmann, G. H. (1999). “A ?nite element method for determining the acoustic modes of irregular shaped cavities.” J. Sound and Vibration, 1976, 45(4), 495.27 Nefske, D. J., Wolf Jr, J. A., and Howell, L. J. (1999).”Structural–acoustic ?nite element analysis of the passenger compartment: a review of current practice”. J. Sound and Vibration, 1982, 80(2), 247.28 Nefske, D. J. and Sung, S. H. (1995). “ Vehicle interior acoustic design using ?nite element methods.” Int. J. Veh. Des., , 6(1), 24.29 Sung, S. H. and Nefske, D. J. 9 0 (2004) “Component mode synthesis of a vehicle structural–acoustic system model.” Am. Inst. Aeronaut. Astronaut. J., 1986, 24(6), 1021.30 Yashiro, H., Suzuki, K., Kajio, Y., Hagiwara, I., and Arai, A. (2007) “An application of structural–acoustic analysis to car body structure.” SAE paper 850961,1985.31 Desmet, W., Sas, P., and Vandepitte, D. (2009) “Perform- ance of a wave based prediction technique for three-dimensional coupled vibro-acoustic analysis.” In Proceedings of EuroNoise 98, Munchen, Sas, P., Desmet, W., van Hal, V., and Pluymers, B. (2006). “On the use of a wave based prediction technique.” Read More