In case of automotive industries, sometimes noise and vibration problems can be expressed in one word, NVH (Noise, Vibration and Harshness). Because of its complex structure, to identify the sound source weak parts or transmission path of vibration would be very difficult. However, the improvement of the NVH performance links directly with the improvement of the value of the product.
For the case of automobile, for instance, squeaking, rattling parts while driving on a rough road or wind noise on an expressway. Booming noise while the engine is idling and the screech from the disk brake etc. are great concern inside a vehicle.
Also, operation noise from electrical appliances or the strange noise due to the expansion and contraction of parts related to the immediate temperature change may be heard. Various problems aggravate engineers.
However, there must be a cause in things, and there must be a means to start moving toward a solution. Would you challenge to solve these problem with us?
When we receive an offer from our customer, the first thing we focus on is extracting tasks which means "true" or "key" problems from communication with customers. We put the customer's problem in order and then using our experience and knowledge along with theirs to work together. Finally, we can establish the task of the problem. The staff always stand behind the customer's point of view and will offer them a wide variety of consulting to meet the needs of the customer.
Numerical simulation is one of the most powerful ways to solve the problem. The boundary element, finite element or the finite difference technique which are best to use to determine the optimal shape position or configuration of acoustical materials can be examined. On the other hand, Biot model simulator is used for determining the sound absorption and sound insulation performance of a single or multi-layered material. With optimal combination of these simulators we can find the most efficient solution to solve the customer's problem.
All these simulators are developed by NAE.
Another best way to solve the problem is experiment analysis. The technology of acoustic experiment analysis is to give a simple, unrefined impression to many people. However, it can be said another state-of-the-art the deep knowledge based on experience and the enginee's capability are all reflected in their work. A well planned experiment gives the engineers positive result of the experiment contributing to precision improvements in a simulation model as well.
There are many variations in acoustic experiment analysis like simple excitation experiment using hammer analysis of the transmission path of vibration and sound or identification / visualization of the source of the noise etc. Here, NAE has been developing main acoustic experiments analysis system and software on its own.
Today the Biot model is widely used to simulate acoustical behavior of multi-layered structure design and its optimization. Also, statistical energy analysis (SEA) is widely used for designing optimum performance of automobile's interior material.
At the same time, in the acoustic experiment analysis field, transmission pass analysis and (TPA) and contribution analysis have also been widely used. In NAE, adding these methods, we have been combining analysis of sound radiation characteristics using p-u probe and evaluating the contribution of noise at driver's ear from various vehicle interior parts, to propose countermeasures for creating a quieter and comfortable space
When driving on rough road conditions, sometimes you may hear strange rattling sounds coming from a certain part of the interior materials. These strange sounds are called Squeak and Rattle (S&R) sometimes low-grade sound (opposite of high-grade quietness), and will be a cause of complaints from drivers. If we can specify the root cause of S&R originated from then we will be able to eliminate it and contribute to the improvement of quality.
Generally the S&R is an occasional event and is difficult to measure and to identify the root cause of them. However, Noise Vision helps this problem because the noise sources where such S&R occurs can be visualized and the engineer can pinpoint them easily.