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Design and Performance Criteria Transport Aircraft Portable Megaphones

S-9A Safety Equipment and Survival Systems Committee
  • Aerospace Standard
  • AS4950B
  • Current
Published 2019-08-22 by SAE International in United States
This SAE Aerospace Standard (AS) provides design criteria and performance tests for portable, handheld, battery-powered, electronic megaphones used by aircraft crew members to provide information and guidance in the event of an aircraft emergency or other non-routine situation.
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Noise and Vibration End-of-Line Production Testing and Analysis Challenges

Bruel & Kjaer North America, Inc.-Chris Moon
Published 2019-06-05 by SAE International in United States
Theoretical modeling continues to play a larger role in noise and vibration engineering; however, until products are perfectly made, there will be a need to evaluate their end of the production line performance. Manufacturing production of a wide range of items has classically involved some amount of subjective and/or evolved objective quality testing along, or at the end of the production line. This testing can have goals of determining product safety, durability, functionality, and/or the vibration/sound quality. A vibration-based measurement approach is frequently used for many of those goals. Often, many modern products utilize some combination of electric motors, internal combustion engines, and power transmission rotational components. The end-of-line testing for many of these rotational components is after many years now heavily refined in the measurement and analysis methods, and the separation of good, bad and marginally bad samples may not always be challenging. It is frequently the non-standard types of products or unique operating conditions, either as subcomponents or assemblies, which may provide unique challenges to the typical measurement and analysis methods. Additionally, depending…
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Development and Application of an Objective Metric for Transient Engine Clatter Noise

FCA US LLC-Anil Charan
InDepth Engineering Solutions-Aniket Parbat
Published 2019-06-05 by SAE International in United States
Several powertrain noise phenomena have been studied over the years. Sound quality metrics, like loudness, sharpness, modulation, and tonality, among others, have been developed to characterize powertrain noises. While these readily available metrics work well on steady state and some transient noises, they do not correlate directly with subjective impressions. Moreover, it is difficult to assign a meaningful single rating for time varying noises that may also be associated with simultaneous variations in frequency content. This paper summarizes the process of creating a vehicle level objective metric and its application to blind noise samples to verify correlation with subjective impressions, particularly in association with clatter noise at moderate engine speeds (2000-3500 rpm) with light to moderate throttle tip-ins. The main results include a single number rating and a rating curve as a function of engine speed useful for comparative NVH assessments of multiple vehicles or of multiple hardware iterations on a development vehicle with objectionable clatter content. The latter application is particularly useful since it gives correct feedback to an uninitiated engineer about the hardware…
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Target Development for Transmission and Electric Motor NVH

FEV North America, Inc.-Todd Tousignant, Alex Ford, Kiran Govindswamy
Ford Motor Company-Justin Dech, Frederick Vanhaaften, Matthew Hettenhouse
Published 2019-06-05 by SAE International in United States
It is a common practice to conduct NVH fingerprinting and benchmarking assessments at the powertrain level, to understand source level noise and vibration. To assess the NVH influence of engine, e-motor, and transmission, sub-system testing is often conducted in addition to full powertrain testing. These powertrain or sub-system investigations provide valuable information regarding the status of “source” level excitations relative to targets and / or competitive powertrains. In the case of transmissions and e-machines, it is particularly important to understand source level tonal content and how this will be perceived at the vehicle level. However, variation in component design results in differences in order content, which complicates the process of objectively comparing multiple products.Multiple methods are presented here for characterizing tonal content of transmission and e-machines, based on assessments conducted in a component hemi-anechoic dynamometer test cell. Ultimately, sound quality is assessed by the customer at the vehicle level. Accordingly, the methods developed incorporate means of cascading results between component level and vehicle level. Furthermore, since the perception of tonal noise content is dependent upon…
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Sound Analysis Method for Warble Noise in Electric Actuators

General Motors-Nathan T. Parker
Published 2019-06-05 by SAE International in United States
Multiple automotive applications exist for small electric motors that are activated by vehicle occupants for various functions such as window lifts and seat adjusters. For such a motor to be described as high quality, not only should the sound it produces be low in amplitude, but it also needs to be free from pulsations and variations that might occur during its (otherwise) steady-state operation. If a motor’s sound contains pulsations or variations between 2 and 8 cycles per second, the variation is described as warble. To establish performance targets for warble noise at both the vehicle and component level a way to measure and quantify the warble noise must be established. Building on existing sound quality metrics such as loudness and pitch variation, a method is established by which processed sound data is put through a secondary operation of Fourier analysis. Thus warble can be reduced to a single value, and in this way, noise engineers have a basis to measure and report warble, and to facilitate product development with A/B comparisons. Depending on its…
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Door Closure Sound Quality Engineering Process

Bruel & Kjaer North America, Inc.-Todd Freeman
Brüel & Kjaer Sound And Vibration A/S-Bret Engels
Published 2019-06-05 by SAE International in United States
An important factor contributing to a customer’s subjective perception of a vehicle, particularly at the point-of-purchase, is the sound created by the passenger doors during closure events. Although these sounds are very short in duration the key systems that control the sounds produced can be highly coupled. Similarly, the necessary efforts required to understand key design criteria affecting the sound can also be highly complex.Within this paper sub-systems affecting the door closure sound are evaluated to understand key structural properties and behaviors toward the contribution to the overall sound produced. This begins with the subjective preferences of typical sounds and the difficulties with both measuring and reproducing these sounds appropriately and leads directly to the target setting and target cascading process. With targets in place, it becomes important to link them with physical measurements of the vehicle and door system to identify the key controlling mechanisms that can be affected through design.The behavior of the door system during a closure event is key for the sound produced and can be studied to understand both the…
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Augmenting Vehicle Production Audit with Objective Data and Sound Quality Metrics to Improve Customer Experience in a Changing Automotive Landscape

Bruel & Kjaer Sound and Vibration A/S-Brian Thom, Gabriella Cerrato
Ford Motor Company-Mark Sturgill
Published 2019-06-05 by SAE International in United States
Vehicle manufacturers face increasing challenges in auditing the build quality of their vehicles while considering increasing consumer demands regarding NVH performance. This effect is compounded with the rise in electric and hybrid vehicles. The ability to audit vehicles for a variety of noise types is becoming increasingly important; these include powertrain noise, road noise, and wind noise. An automated measurement system was developed with specific algorithms and sound quality metrics to not only audit vehicle production quality but to add objective data, pass-fail criteria, and trend analysis.
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A Case Study on Golf Car Powertrain NVH Sources and Mitigation Methods

Club Car, LLC-Adam Clark
Roush Industries, Inc.-Steven Carter, Kenneth Buczek, Mayuresh Pathak
Published 2019-06-05 by SAE International in United States
The golf market has remained flat in North America. Whereas, it has grown worldwide. A trend is seen where the number of young adults and adults over the age of 65 years involved with the game has increased. The demographics in golf showing the most growth also have high standards for the operation of the golf car. They have transcended their expectations to align with some of the qualities expected of automobiles. There is a shift in consumer expectations. Moreover, the market competition has also increased. This drives the OEMs to deliver refined golf cars with NVH being a key aspect in development. This paper showcases a recent study to improve the powertrain N&V performance of an internal combustion engine golf car. Primarily, a test-based approach is followed. Chassis rolls and on road testing are performed for benchmarking and target setting. System and component tests are performed to root cause issues. The tests further help to provide input for mitigation methods for application on the golf cars. Structural modifications address structure-borne noise and perceived vibration.…
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Sound Quality Prediction Modelling for the Transient Sound of Vehicle Door Latch Closure

Tongji University-Chang Jin, Tianpeng Zhang, Liying Ma, Tao Zhang, Yi Zhou
Published 2019-06-05 by SAE International in United States
Door latch closure noise has contribution on sound quality of vehicle door slam sound. This paper focuses on the modelling of sound quality for door latch closure sound. 24 various latch closure sound samples were recorded to be evaluated subjectively. A novel Dynamic Paired Comparison Method (DPCM) was introduced for subjective evaluation. By eliminating the redundant comparison pairs the DPCM dramatically reduced the evaluation work load comparing to the traditional Paired Comparison Method (PCM). Correlation between subjective evaluation results and psychoacoustic metrics was analyzed to find out the most relevant metrics as inputs for the subsequent prediction model. Besides, the shudder effect induced by multi-impact of latch components during closing movement was also found strongly affecting the subjective perception of door latch closure sound. Therefore, a new metric Shudder Level which is graded in 3 levels describing this shudder effect was developed and then quantified as one of the model inputs. The sound quality of door latch closure was modeled by means of Multi-Linear Regression Function (MLRF) both with and without the Shudder Level. The…
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Target Setting Process for Hybrid Electric Drives Using TPA, Jury Study, and Torque Management

FCA US LLC-Vinod Singh, Anil Charan
InDepth Engineering Solutions-Aniket Parbat
Published 2019-06-05 by SAE International in United States
The idea of improved efficiency without compromising the “fun to drive” aspect has renewed the auto industry’s interest toward electrification and hybridization. Electric drives gain from having multiple gear ratios which can use advantageous operating set points thus increasing range. Furthermore, they benefit significantly from frequent decelerations and stopping as is experienced in city driving conditions. To recuperate as much energy as possible, deceleration is done at high torque. This presents an interesting but serious sound quality issue in the form of highly tonal whine harmonics of rapidly changing gears that do not track with vehicle speed thus being objectionable to the vehicle occupants. This paper presents an NVH target setting process for a hybrid electric transmission being integrated into two existing vehicles, one belonging to the premium segment and another aimed at enthusiasts with off-road applications. The demand for power has shifted from mechanical domain into electrical domain, and as such, the solution to electric drive NVH issues also lay partly, in the way these drive systems are calibrated. A time-domain Transfer Path Analysis…
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