Accelerometers, Preamplifiers, Microphones, Signal Conditioners, Sound Level Meters, and Accessories
NVH - Noise, Vibration & Harshness
NVH stands for Noise, Vibration, and Harshness and is an industry term associated with the treatment of vibration and audible sounds. Noise denotes unwanted sound; and hence the need to negate these sounds and vibrations. Vibrations above and below a specific range may not be detectable to the human ear, but may still require treatments for improved product performance and longevity. The frequency of the noise is paramount, as it dictates which method of treatment or what material will work best. Harshness usually refers to treatments of transient frequencies or shock. NVH refinement has become an essential vehicle development attribute, as it is directly related to legislative compliancy, product quality, driving pleasure, brand image, and most importantly customer satisfaction.
Advanced NVH test methods and analytical simulation tools are prerequisites in today’s fast paced automotive market to ensure front-end optimization of lowered levels of sound and vibration and enhanced design while still maintaining a balance with fuel efficiency, driveabilility, and system & component performance. PCB Piezotronics, Inc. offers a complete sensor and instrumentation solution for the measurement of NVH attributes from concept through to post production assessment. Due to shortened product development cycles, many automotive manufacturers and their suppliers are choosing to consolidate NVH testing with other development activities including: road load data acquisition, powertrain performance testing, and calibration development, to name a few. PCB® facilitates this trend with diverse sensor offerings in acceleration, acoustic, pressure, force, torque, load, and strain technologies allowing an efficient test and instrumentation strategy to capture performance and attribute measurements.
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The concept stage of the vehicle development process not only determines the most fundamental architecture of the automotive structure, but also offers an opportunity to reduce the amount of downstream development effort needed to achieve performance and attribute targets by optimizing core structures and system configurations and striking a balance between fuel economy, emissions, performance, ride, and NVH. Typical NVH activities could include:
- Structural Computer Aided Engineering (CAE) and modal analyses
- Dynamic system simulations
- Powertrain mounting strategies
- Body mounting concepts
- Suspension configurations
- Vehicle simulations
- Competitor benchmarking
During the concept stage, performance and attribute targets are defined based on market expectations and cascaded down to system and component specifications.
Powertrain NVH Development
Due to the ever increasing importance of fuel economy, performance, and NVH in the development of today’s engine, the NVH engineer must work closely with the engine and powertrain calibration and combustion engineers to strike a balance between the efficiency of combustion and the reduction of combustion forces that result in noise, vibration, and driveability issues. This development often takes place in a performance and emissions test cell where a less than ideal acoustic environment predicates the use of accelerometers as an indication of relative engine forces and inferred noise strength. Engine component suppliers also play a strong role in overall powertrain noise target attainment. From structural members such as engine blocks, oil pans, valve covers, and mount brackets to integrated systems such as transmissions, fuel injectors, power steering pumps, and turbos; component and engine manufacturers alike spend significant test time in hemi-anechoic dynamometer test cells to develop systems to meet the NVH targets that cascaded from the concept phase. These tests could include:
- Engine NVH benchmarking
- Sound intensity mapping
- Source identification
- Modal analysis
- Ancillary noise development
- Turbo noise development
- Intake noise development
The impact of this development work is focused on achieving overall vehicle NVH targets, specifically targeting overall engine noise and sound design and inputs into the engine mounts. PCB® designs and manufactures a line of sensors developed for powertrain and NVH applications that take into account the harsh environment associated with powertrain testing. High temperature and water and dust resistant microphone systems, along with rugged, hermetically sealed accelerometers and pressure sensors are used to make measurements in this environment.
Vehicle NVH Development
The integration of the powertrain into a vehicle structure is the most critical activity in the development process. Reduction of structure-borne noise and vibration paths are minimized in this phase through fine-tuning of powertrain, exhaust, and body mounts. Airborne noise paths are reduced through sound package development. This fine-tuning, along with intake and exhaust development, account for the interior sound design of the vehicle. As with powertrain NVH development, the NVH engineer must also work with the calibration engineer to assess possible trade-offs with fuel economy, emissions, NVH, and driveability; and with the ride & handling engineer to assess trade-offs with ride quality and vehicle handling. Today’s NVH engineer has numerous analytical and experimental tools and tests to aid in the systematic and continuous NVH development leading up to the production build of the vehicle, including:
- Issue resolution using Noise Path Analysis (NPA)
- Sound Quality Analysis (SQA)
- Intake and exhaust orifice noise refinement for sound design
- Noise Transfer Functions (NTF)
- Modal analysis for structural optimization
- Engine mount tuning
- Transmission loss for acoustic package refinement
- End-of-line NVH test methods for quality control
- Noise masking studies for pass-by and curb-side noise reduction
- Acoustical array set-ups for noise identification
New standards and customer expectations drive the need to lower noise and vibration levels in cars, tractors, construction equipment, motorcycles, and snowmobiles. This tightens the requirements for wind noise, road noise, powertrain noise, road idle quality, and driver comfort. These attributes are indicators of quality. PCB® provides the highest quality sensors for NVH testing backed by our Total Customer Satisfaction guarantee.