Noise Vision Applications Examples

Sound and Vibration

Improving Noise performance in vehicles

In automotive industries noise and vibration problems are 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. 

Phenomena like squeaking and rattling parts while driving on a rough road orwind 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. 

However, there is always a cause in things, and there must be a means to start moving toward a solution. 

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.

Experiment analysis is another best way to solve the problem. 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, transfer path analysis (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.       

Courtesy of Nittobo Acoustic Engineering Co. Ltd. – Tokyo – Japan

Truck engine noise sources identification

Truck engine noise present several individual sources which are all correlated due to engine rotation. The task of separate individual contribution and classify sources in terms of energy cannot be achieved with traditional measurements and requires several calculation. Noise Vision beam forming – focusing capabilities – represent a valid experimental approach; fast and reliable, for overall noise decomposition in single sources.

Measurement are performed both in stationary rotation as well as in ramp up/down, obtatining acoustic images as a function of engine rotation.

Noise VIsion has a standard angle resolution of 5 degree which can be as low as 2 degree to achieve a unbeatable space resolution even for close sources.

Courtesy of SCS-Euroacoustic – Avigliana TO – Italy

Theater sound investigation

Studying the acosutic in a theater is one of the most delicated task because the quality of acoustic depends mainly from geometry and materials.

One of the principal interest is to detect sound reflection areas and reflection index and the use of the Noise VIsion beam forming is a rather good method in terms of precision and time saving.

An interesting experience has been performed in “Teatro Regio” Torino – Italy, by placing the Noise VIsion transducer in several position on grouns theater, while a loudspeaker was placed in the middle of the scene.

in less than half hopur, including instrument mounting, cabling and boot-up. the acoustic study of the theater was done! Sound specialist and architects got all necessary information to judge the quality od the sounding and possibly improving the performances, based on the acoustical geometry information and energy relationship.

Courtesy of SCS-Euroacoustic – Avigliana TO – Italy

Acoustic diagnosing on Industrial Noise Sources

When we examine a countermeasure against noise in a large-scale factory, it is necessary to investigate sound sources supposed comparatively influential in detail, and to calculate noise propagation condition repeatedly, using a complex computer simulation . 

When a factory has a large amount of complex noise sources, there is tremendous amount of work needed to take a detailed measurement. Moreover, a vast amount of time will also, have to be spent on performing an acoustical simulation in-house. 

However, using the omni-directional sound source analyzing system called ‘Noise Vision’ which has the potential of separating the entire noise, it can diagnose the condition of the noise source easily. 

By using this noise diagnostic result, it is easy to verify the important point and priority of countermeasure against factory noise. Depending on factory’s scale, for example, when we carry out measurement using ‘Noise vision’ for 2 days, it is possible to turn in the report attached the following result of the analysis in the evening of the 2nd day. 

Courtesy of Nittobo Acoustic Engineering Co. Ltd. – Tokyo – Japan