February 04th, 2021
We have a semi-anechoic chamber used for noise, vibration and harshness (NVH) testing at our Bristol, UK site. It is helping us to diagnose and improve the sound performance of our customer’s systems. It allows us to gather accurate data to highlight areas for improvement and evaluate potential solutions to achieve NVH targets, no matter the industry.
Whilst our main focus is on squeak, rattle, and whine, we can also assess mechatronic operational noise; vehicle structural and airborne transfer functions and vehicle sealing. In the chamber we can test individual components and entire assemblies, up to and including vehicles. Our analysis ranges from simple noise and vibration through order analysis, transmissibility, tonal metrics and equivalent body hole size.
There can be a big difference between noise level and the subjective reaction to noise.
Noise level, whilst relatively simple to measure in the semi-anechoic chamber, does not always get to the root cause of the noise, squeak or rattle problem.
Subjective reaction to noise, also called psychoacoustics, or simply sound quality involves the human reaction to noise. To the layman this may be as simple as identifying a noise as good or bad. When explaining sound quality, an example is often useful: consider the electric window motor in a car door. When it is opened or closed, the corresponding sound may be smooth and minimal, meeting the customer’s expectations and giving them the comfort that the motor is working well and the system is of high quality. However, if that motor was to make loud clicks or abrasive sounds the user could believe that the motor was faulty or broken. To achieve the human perception of good sound quality the application needs to meet a target, which will include psychoacoustic parameters.
To ascertain sound quality, tests can be run to measure and capture the human response to different noises. Pitch, tone and frequency can be measured as each one can have an impact on whether the listener finds the sound acceptable or irritating. Sound quality is subjective and requires expertise and data analysis to decipher which frequencies or tones the target customer will like or dislike. For example, a vacuum cleaner with a low frequency hum vs one with a high frequency whine.
The output data from these tests can be used to manage appliance noise so it falls within the range of acceptance, or target parameters. Using our semi-anechoic chamber, these tests are available to our customers to improve their products NVH outputs.
Our semi-anechoic chamber in Bristol meets the following technical specifications:
• Semi-anechoic noise chamber
• Chamber dimensions: 7.5m x 7.5m x 4.5m
• 20dB(A) noise floor
• 100Hz lower frequency limit
• Vibration isolated floor
• Shaker systems up to 10kN
• 2 - Axis Slip Table
We can carry out a wide range of tests in our semi-anechoic chamber. To give you some idea, below is a short list of some of the tests that we are capable of performing:
• 3 dimensional testing of full seats to operational input or sign-off test
• Steering Rack testing to operational input or sign-off test
• Sub-assembly component NVH investigation
• Vibration and Airborne Noise Transfer Assessment
• Sound Power Measurement
• Electric Motor NVH development under operational Speed and Torques
• Mechatronic Operational NVH assessment
With drones becoming increasingly used for delivery in urban environments and as vehicles become quieter on the road, noise nuisance from drones will become more common and noticeable. A source analysis on a drone highlighted that high frequency noise was dominated by the drone’s motor. This allowed us to isolate where changes would make the most difference to the perceived noise quality.
Until recently, at low speeds, the most significant noise emitted from a car was the noise from the internal combustion engine (ICE). This noise would often mask other noises. With the increase in hybrid and electric vehicles, those other noises are becoming more noticeable. Engineers now need to focus on improving the squeak and rattle performance of internal parts and components, for example in a seat frame. We can support this with 3-axis testing to simulate road input to systems inside a vehicle and locate where squeaks and rattles are coming from to pinpoint areas for improvement.
In the semi-anechoic chamber, we can carry out sound power analysis. House-hold appliances need to meet legislative sound power levels. In addition to this, customers of modern, high-end appliances expect products that are quiet and can be used with as little disturbance as possible. The sound power analysis test provides a sound energy value for the appliance independent of the environment or the distance from the source. With this test we can confirm if any changes to the appliance would give a reduction in sound power. This can be supported by further auxiliary NVH tests to determine what changes should be made. With this test data you can compare your product directly with others and give your product the NVH edge.
With the transition to hybrid and electric vehicles, ICE engine noise that we expect and have come to accept, has been replaced with tonal motor whine. With our electric motor testing facilities and equipment, we can test motors under normal operating conditions which can identify frequency response and order content where whine becomes present. With this test data we can make changes to the motor such as using a tolerance ring to mount the stator to change the NVH properties. We can then re-test the motor to confirm the reduction in whine.
Bearings are a possible source of self-generated and transmitted noise in systems. This could be caused by a number of reasons: system tolerances, wear, thermal expansion of dissimilar materials and transmissibility across the bearing joint. By carrying out a 3-axis shaker test on a bearing mounted with and without a tolerance ring we were able to prove the NVH improvement potential achieved by using a tolerance ring.
The components manufactured by Saint-Gobain, such as NORGLIDE® Bearings, RENCOL® Tolerance Rings and SPRINGLIDE™ Spring Energised Bearings have an important role in reducing squeak, rattle and whine in systems. Additionally, Pritex, a Saint-Gobain sound pack supplier has the ability to test the performance of treatments in entire assemblies. This enables us to support component and vehicle development to achieve NVH targets.
All of our tests can help you improve the sound level and quality of your system. The results will identify areas for improvement or where products can be replaced to reach the sound results you need from your system; helping you to achieve sound performance standards, customer expectations or both.
Here at Saint-Gobain we are proud of our heritage in innovation and creativity. The semi - anechoic chamber in Bristol allows us to continue that tradition with a testing facility that is readily available and dedicated to innovation and development of new and improved products.
Within our team we have a dedicated NVH expert who can provide advice and recommendations on your individual products and systems. Developing solutions with Saint-Gobain opens doors to our testing capabilities and experts helping you hit NVH targets and improve the NVH experience for your customers.
To make an enquiry, or for more information on how our chamber could be of assistance; to enquire about hiring the chamber or vehicle sealing, please Contact Us.