Browse Topic: Sound quality

Items (243)

Verifying large alternate product code for an Surface Vehicle RP document - JRP001

JA/NEW/RP000000000000000000000001_202511 (Current)

11/24/2025

Verifying large alternate product code for an Surface Vehicle RP document - JRP001

Active Safety Systems Standards Committee

Snapshot Array Design Considerations for Rotorcraft Noise Characterization

F-0081-2025-0061

5/20/2025

Acoustic flight testing of rotorcraft often involves generating noise source hemispheres to gain an understanding about the aircraft's acoustic emissions. However, aerodynamically complex Urban Air Mobility and Future Vertical Lift vehicles may not maintain a steady aerodynamic state during flight, making source hemispheres measured using traditional linear arrays unreliable or difficult to interpret. To address this challenge, all emission angles need to be measured simultaneously. This has lead to the concept of the two dimensional 'snapshot' array layout. A mathematically defined microphone distribution was utilized to achieve uniform coverage on the source hemisphere. Within the chosen distribution, two lower microphone count distributions are embedded, allowing for a comparison of the effects of number of microphones. The array was deployed as part of a joint Army/NASA acoustic research flight test in July of 2024. Data were collected using an MD530F helicopter as the test vehicle, executing both steady and unsteady flight. Analysis of the array resolution is used to determine adequate channel count and spatially varying sensitivity to array density.

Houston, Mary, Stephenson, James, Pascioni, Kyle, Stutz, Colin

Medium-Sized Helicopter Noise Abatement Flight Test

F-0076-2020-16497

10/5/2020

An extensive flight test campaign was recently completed, which aims to reduce the operational noise generated by helicopters in an effort to improve community acceptance. Using a ground-based microphone array, acoustic measurements were acquired on helicopters in the medium-sized vehicle weight class over a number of flight conditions including steady level flight, steady descents, and approaches. While data were collected across four helicopters, the Leonardo AW139 and Sikorsky S-76D will be the focus of this paper. Source noise hemispheres are computed for the steady test points, but the ground noise contours measured during approach conditions cover only a small portion of the area impacted by noise because of practical constraints on the size of the deployed array. Thus, the Noise Informed Community Environment Operations Planning System (NICEOPS) in conjunction with the flight test data was used to estimate how changes in the approach procedures impact noise exposure over a larger ground area. It was found that even small longitudinal accelerations can have a substantial influence on the noise generation processes during approach and must be modeled appropriately to develop new flight procedures which minimize the acoustic impact on the ground.

Pascioni, Kyle, Watts, Michael, Stephenson, James, Greenwood, Eric, Smith, Charles

Road Noise Evaluation by Sound Quality Simulation Module

2020-01-12754/14/2020

An objective evaluation of sound quality is a technical bridge connecting sound pressure level (SPL) and human auditory sensation. In this paper, an algorithm is proposed for calculating objective evaluation parameters of sound quality (including loudness, sharpness and articulation index), considering acoustic characteristics of human external ear, middle ear and inner ear to reflect auditory sensation. A sound quality simulation (SQS) module is coded according to the algorithm. The module is used for evaluating sound quality of road noise from an SUV in three steps. Firstly, interior noise is predicted by integrating finite-element method (FEM), hybrid FE-SEA method, and statistical energy analysis (SEA) for low frequency (20~315 Hz), medium frequency (315~500 Hz), and high frequency (>500 Hz) in 1/3 octave band, respectively. The predicted interior noise SPLs are compared with the measured results, with deviations less than 3dB in average. Secondly, the sound quality parameters are calculated using the predicted SPLs in the SQS module. The predicted and measured loudness, sharpness, and articulation index are compared, with average deviations less than 5%. Finally, the predicted interior noise is filtered by the SQS module in 1/3 octave band, to determine the dominant contribution bands for the sound quality parameters. Several optimized designs are implemented to optimize the sound quality parameters, and validated by experiments.

Gu, Perry, Mao, Jie, Chen, Zhidong, Ding, Zhi, Cheng, Lei, Zhu, Zhenying, Peng, Hong

5 Ws of PAWS Smart Headphones

TBMG-361993/1/2020

Pedestrians who wear headphones or earbuds to listen to music, text, or talk on smartphones while walking, putting themselves at risk by tuning out the traffic around them.

5 Ws of EarEcho

TBMG-3569312/1/2019

Anyone who uses a smartphone with in-ear earphones.

Door Closure Sound Quality Engineering Process

2019-01-15236/5/2019

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 nearfield acoustic field generated as well as the structural vibration patterns. This can be accomplished during a closure event and linked to in-lab assessments that allow for greater repeatability and flexibility. Boundary conditions for the door structure are also relevant to the sound produced, including the transmission of forces into the seals, latch and striker, and bump-stops, as well as understanding the effects from the vehicle interior cavity. Once the key controlling mechanisms affecting the door closure sound quality are understood, it allows for the sound produced to be shaped as desired. This can be accomplished by leveraging analytical modeling efforts, supplemented with necessary test data, to design key components and systems to achieve the desired sound.

Freeman, Todd, Engels, Bret

Development and Application of an Objective Metric for Transient Engine Clatter Noise

2019-01-15196/5/2019

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 changes he or she is proposing. Further this could help in data driven decision making during cost versus benefit assessments.

Parbat, Aniket, Charan, Anil

Sound Quality Prediction Modelling for the Transient Sound of Vehicle Door Latch Closure

2019-01-15176/5/2019

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 results show that the model which takes the shudder effect into account gives a better prediction on door latch closure sound quality.

Jin, Chang, Zhang, Tianpeng, Ma, Liying, Zhang, Tao, Zhou, Yi

Sound Analysis Method for Warble Noise in Electric Actuators

2019-01-15216/5/2019

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 source, warble is manifested as either a sinusoidal variation in loudness, or as a sinusoidal variation in a motor’s rotational speed. Regardless of source, pulsations between 2 and 8 Hz are particularly annoying and portray a low-quality perception of a sound that is expected to be steady and even. By using the methods and calculations presented in this paper, a clear indicator of both loudness warble and pitch warble can be discerned from any recorded steady-state motor noise.

Parker, Nathan T.

Target Setting Process for Hybrid Electric Drives Using TPA, Jury Study, and Torque Management

2019-01-14536/5/2019

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 (TPA) model was developed for both vehicles, by virtually installing the hybrid transmission into the vehicle, thus predicting interior noise in several gears and simulating the brake regen coast downs at varying torque levels. Road and wind noise masking was added to these predictions taking care that the summations were correctly done at same vehicle speeds for which a program was written using a commercially available numerical computing tool. Extensive jury studies were then conducted to determine NVH no-fly zones and the torque management strategy for the two vehicles during brake regen events. Requirements and strategy for the two vehicles were different since they presented different levels of road and wind noise masking. To validate the NVH targets, another jury compared the finalized strategy with a premium target vehicle fitted with a similar hybrid system. This target-setting approach was useful in getting an upfront idea of the NVH risks without any system modifications. It then circumvented the need of re-developing expensive acoustic package and/or gear optimization that would be otherwise needed to mitigate the risks, with co-operation from calibration teams, while still being able to meet their regenerative braking targets in every gear for the two vehicles.

Singh, Vinod, Parbat, Aniket, Charan, Anil

Augmenting Vehicle Production Audit with Objective Data and Sound Quality Metrics to Improve Customer Experience in a Changing Automotive Landscape

2019-01-15316/5/2019

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.

Thom, Brian, Cerrato, Gabriella, Sturgill, Mark

Design and Validation of Low-Cost Intensity Probe

2019-01-14626/5/2019

Sound intensity measurement techniques that used a two-microphone configuration, were first developed in the late 1970s. Originally, the focus was on improving precision during testing or post-processing. However, with the advent of modern, sophisticated equipment, the focus has shifted to the apparatus. Availability of phase-matched microphones has made post-test correction obsolete as the microphones eliminate a majority of the errors before the data is even collected. This accuracy, however, comes at a cost, as phase-matched microphones are highly priced. This paper discusses employing the method of improving post-processing precision, using inexpensive, current equipment. The phase error of the system is corrected using a simple calibration technique and a handheld phase calibrator that is similar to the one used for amplitude calibration of microphones. The intensity probe and calibrator is manufactured using rapid prototyping and the executable software that goes with the probe is designed in NI LabVIEW. The entire setup uses inexpensive parts to lower the cost and modern software to compensate for the errors due to these parts. The design of the probe and the accompanying software will be discussed in the paper. Additionally, the accuracy of the probe will be compared to a commercially available sound intensity probe and the results will be discussed.

Gundre, Karan, Barnard, Andrew

Noise and Vibration End-of-Line Production Testing and Analysis Challenges

2019-01-14646/5/2019

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 on how new the end-of-line evaluation process is to a manufacturing company, then the process may be aided with additional steps beyond typical site survey and final pass/fail system integration. These additional steps may include noise and vibration troubleshooting for source localization, informal or formal listening studies to rank good, bad and marginal samples, and the investigation of non-standard analysis methods. The goal is to always be able to reach performance standards at the end of the production line. Sometimes, the methods used for evaluation at the end of production may also then be refined and extended into lifelong condition monitoring of the product in a final application.

Moon, Chris

A Case Study on Golf Car Powertrain NVH Sources and Mitigation Methods

2019-01-14786/5/2019

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. Component modifications and additions address three key aspects. They reduce air-borne noise, decrease overall SPL, and improve sound quality for brand identity. These mitigation techniques are applied on the golf car. Jury evaluations correlated with on-road testing results for golf car improvement. The improvements were in both sound quantity and sound quality.

Carter, Steven, Buczek, Kenneth, Clark, Adam, Pathak, Mayuresh

Paradigm shift in NVH

19AUTP06_026/1/2019

A new wave of vehicle technologies is changing the way Brüel & Kjaer attacks noise, vibration and harshness. When you're in the business of NVH solutions, you get to know noise and vibration up close and personal. And for these experts, it can be difficult to sequester the ‘N and V’ throughout their own day. Ask Dr. Gabriella Cerrato, manager of global sound and vibration engineering services at Brüel & Kjaer. “I can't be in a hotel room and not be aware of things like the refrigerator compressor, the ice maker, or the air conditioning,” she noted. “Although I'm not a geek about it-I don't immediately ponder the sources and potential noise paths of the hotel HVAC, for example-it sometimes drives me nuts.”

Brooke, Lindsay

Automotive Engineering: January 2019

19AUTP011/8/2019

Pickup shocker With the R1T, Rivian emerges as the startup most likely to build the electric vehicle all of America will want to own. Plastics spur tech innovations The SPE Innovation Awards recognize vehicle OEMs and their supply chains for novel material developments and applications. A lesson in Multiphysics OEM engineers reveal how new software from Comsol improved their modeling and analysis of EV battery performance and audio-system sound quality. Heat pumps-expensive but worth it? They add 50% to the cost of the Jaguar I-Pace climate-control system, but improved designs are indicating the cost can be recovered-whether for a Jag or an electric school bus. Editorial Rivian out-innovates the Detroit 3 SAE Standards News SAE updates J3016 automated-driving graphic Supplier Eye Suppliers shift focus to rising costs The Navigator The not-so-hidden cost of "free" What We're Driving BP's Nexcel sealed-cell oil system an alternative for controlling GHG emissions BorgWarner demos next-step electrification components Ford Advanced Manufacturing Center investment to speed production innovations JLR uses predictive technology to reduce motion-sickness risk Jeep's Gladiator takes up arms in midsize-pickup battle Porsche reveals eighth-generation of fabled 911 Ford engineers a tech barrage with 2020 Lincoln Aviator Palisade SUV new Hyundai flagship Hyundai Nexo out-spaces Toyota and Honda FCVs Q&A AAM's Jeffrey Nichols discusses drive axle innovations

Mitigating Sound with Advanced Pump Technology

TBMG-3324811/1/2018

Medical technology continues to evolve toward diagnosis and treatment devices that are closer to the patient, or even in the patient's home. Compression therapy, wound therapy, dialysis, point-of-care testing, and portable oxygen concentrators are just a few such instruments. Many of these instruments include active components that create noise that can impact a patient's sleep quality and level of comfort and can create stigma around using device. A diaphragm pump, which produces gas flow and pressure, is often one of the main sound contributors, and reducing the noise it makes can significantly affect the overall noise generated by the device. Engineers must balance performance needs and sound quality with increasing demands for miniaturized and application-specific equipment. These concerns have created a growing challenge to reduce the amount of noise generated by the device and its components.

Acoustic Waves Offer Treatment for Kidney Stones

TBMG-3324511/1/2018

Researchers are investigating the use of time reversal (TR) signal processing to focus waves sound with high amplitudes in a room. In biomedical applications, focused ultrasound can be used in lithotripsy procedures for treating kidney stones or to target brain tumors.

Auralization of Rotorcraft Periodic Flyover Noise from Design Predictions

F-0074-2018-12664

5/14/2018

ABSTRACT This paper combines the synthesis and propagation of rotorcraft sounds, or auralizations, with their noise predictions and design optimization to incorporate human response into the process of creating low-noise rotorcraft. The NASA Auralization Framework is described and used to auralize the sounds of an AS350 helicopter main rotor at a ground observer from predicted acoustic pressure time histories. This paper uses spherical phase interpolation as part of the sound synthesis. This interpolation is an improvement over the linear phase interpolation described in previous work, which can introduce artifacts in the auralized sound. The effects of noise prediction source resolution are discussed. Two AS350 helicopter main rotor planform optimizations using certification noise metrics as the objective function are performed. One objective function is the Effective Perceived Noise Level metric and the other is the A-weighted Sound Exposure Level metric. The planform optimization includes determining trim state, predicting and propagating source noise, and changing design variables to affect the noise metric. Auralizations of the rotor sounds are computed, and due to their time domain nature, enable a more thorough exploration of sound quality metrics applied to the rotor sounds than traditional 1/3-octave predictions. These other metrics can be used to assess community annoyance and help develop human perception metrics that can potentially be incorporated into the helicopter design cycle.

Krishnamurthy, Siddhartha, Aumann, Aric, Rizzi, Stephen, Douglas, D.

Paper-Thin Device Acts as a Loudspeaker and Microphone

TBMG-2802612/1/2017

A paper-thin, flexible device was created that can generate energy from human motion, and can act as a loudspeaker and microphone. The transducer is ultrathin, flexible, scalable, and bidirectional, meaning it can convert mechanical energy to electrical energy, and vice-versa.

Traditional and Electronic Solutions to Mitigate Electrified Vehicle Driveline Noises

2017-01-17556/5/2017

Hybrid powertrain vehicles inherently create discontinuous sounds during operation. The discontinuous noise created from the electrical motors during transition states are undesirable since they can create tones that do not correlate with the dynamics of the vehicle. The audible level of these motor whines and discontinuous tones can be reduced via common noise abatement techniques or reducing the amount of regeneration braking. One electronic solution which does not affect mass or fuel economy is Masking Sound Enhancement (MSE). MSE is an algorithm that uses the infotainment system to mask the naturally occurring discontinuous hybrid drive unit and driveline tones. MSE enables a variety of benefits, such as more aggressive regenerative braking strategies which yield higher levels of fuel economy and results in a more pleasing interior vehicle powertrain sound. This paper will discuss the techniques and signals used to implement MSE in a hybrid powertrain equipped vehicle. MSE utilizes powertrain signals from the vehicle bus to determine which harmonics need to be veiled and at what output level. By enhancing and complementing the naturally occurring electric propulsion sounds, it’s possible to create a more continuous and rich hybrid powertrain sound through the hybrid transition states. As MSE is adding noise to improve the overall sound in the vehicle, this feature can also be utilized to make the vehicle sound heartier and more refined for acceleration or deceleration events while simultaneously masking unwanted tones. The MSE concepts discussed in this paper are covered under US patent 9237399.

Valeri, Frank C., Lagodzinski, James T., Reilly, Scott M., Miller, John P.

Characteristics of Non-Stationary Sources of Wind Noise Measured with a Surface Pressure Array

2017-01-17856/5/2017

Measurements of interior wind noise sound pressure level have shown that dBA and Loudness are not adequate metrics of wind noise sound quality due to non-stationary characteristics such as temporal modulation and impulse. A surface microphone array with high spatio-temporal resolution has been used to measure and analyze the corresponding non-stationary characteristics of the exterior aero-acoustic loading. Wavenumber filtering is used to observe the unsteady character of the low wavenumber aero-acoustic loading components most likely to be exciting glass vibration and transmitting sound.

Bremner, Paul, Clifton, Scott, Todter, Chris

Active Cancellation of Exhaust Noise over Broad RPM Range with Simultaneous Exhaust Sound Enhancement

2017-01-17536/5/2017

Demands for engines to operate at low-frequency firing order are increasing in the automotive market. This requirement is driven by consumer and regulatory demand for vehicles which are more efficient in the use of fuel. As a result, engine and transmission technologies have been developed which permit operation of engines with fewer cylinders at increasingly low RPM’s. The resulting low frequency exhaust noise is more difficult to attenuate than in vehicles in years past. At the same time, vehicles often have less packaging space for mufflers, when larger volume would otherwise be needed to attenuate at lower frequencies. A further challenge is the demand for increasingly refined performance sounds from the exhaust systems of premium cars despite the technical obstacles involved in even maintaining sound quality. Finally, legally permissible sound levels are decreasing in some markets. These market and regulatory demands require new solutions. Technology has been demonstrated using an ANC system. The system uses the operating principle of ANC, using a feed-forward control mechanism. This system has now been demonstrated to attenuate multiple firing orders by sound cancellation down to 1000 RPM on a 4 cylinder gasoline turbocharged engine. It has also been demonstrated to simultaneously attenuate undesirable orders and accentuate desirable orders. This has been demonstrated in a vehicle with a 4 cylinder TC engine and also in a V8 application operating in 4 cylinder mode, where such desired engine order sounds could not be expected typically.

Riddle, Jack Hall, Bemman, Ya-Juan, Frei, Tom, Wu, Sihui, Padalkar, Ishang

Assessment of Lightweight Automotive Glass Solutions on Interior Noise Levels & Sound Quality

2017-01-18146/5/2017

The automotive industry continues to develop technologies for reducing vehicle fuel consumption. Specifically, vehicle lightweighting is expected to be a key enabler for achieving fleet CO2 reduction targets for 2025 and beyond. Hybrid glass laminates that incorporate fusion draw and ion exchange innovations are thinner and thereby, offer more than 30% weight reduction compared to conventional automotive laminates. These lightweight hybrid laminates provide additional benefits, including improved toughness and superior optics. However, glazing weight reduction leads to an increase in transmission of sound through the laminates for certain frequencies. This paper documents a study that uses a systematic test-based approach to understand the sensitivity of interior vehicle noise behavior to changes in acoustic attenuation driven by installation of lightweight glass. Specifically, this study evaluates the influence of a lightweight windshield on wind, road, and powertrain contributions to vehicle interior noise. To facilitate this assessment, operating tests were conducted utilizing variable operating conditions and road surfaces such that varying balances of powertrain, wind, and road-induced interior vehicle noise could be evaluated. A time-domain noise transfer path analysis (TPA) was conducted, including multiple sources to quantify the contributions of powertrain, wind, and tire-induced noise. Prototype glass treatments were installed, and differences in measured airborne noise transfer functions were used to update the TPA model for interior noise prediction. To eliminate the influence of test reproducibility, a consistent set of “source” data was used throughout this study. Based on the results of the iterative TPA analysis, the influence of glass acoustic performance on interior sound was assessed. The use of a time-domain TPA process facilitated both subjective and objective assessment of interior sound quality. Based on the results from this analysis, minimal degradation was observed in vehicle-level NVH performance using the hybrid laminate comprising of lightweight glass, relative to conventional laminate and the lightweight glass was assessed to be a viable enabler for the vehicle application considered.

Tousignant, Todd, Govindswamy, Kiran, Bhatia, Vikram, Polasani, Shivani, Fisher, W Keith

Audio Synthesis and Sound Quality of Automotive Air-Conditioning Systems

2017-01-18876/5/2017

While electric and hybrid vehicles are becoming increasingly common, the issue of engine noise is becoming less important, because it does not dominate the overall noise perceived in the passenger compartment in such vehicles anymore. However, at the same time, other sound sources such as air conditioning, start to emerge, which can also cause annoyance. The CEVAS project, involving VALEO, CETIM, University of Technology of Compiègne, ESI GROUP and GENESIS, deals with the acoustic simulation and perception of automotive air-conditioning (HVAC) and electric battery cooling (BTM) systems. While the other partners focused their work on the aeroacoustic characterization, modeling and simulation, GENESIS’ part in the project is dedicated to HVAC sound synthesis and perception. In order to do the synthesis of the acoustic spectra provided by the partners of the project, an additive model was used. Its ability to reliably reproduce sound recordings was addressed through a listening experiment, which also helped in defining the necessary resolution of the input spectra in order to produce convincing sounds. Finally, various HVAC sounds, including different models, operating modes and airflow rates, were assessed by means of a psychoacoustic method involving two listening experiments: a verbalization task, and a semantic differential task. The results were statistically analyzed and a robust sound quality model based on loudness and tonality metrics was proposed.

Minard, Antoine, Lambourg, Christophe, Boussard, Patrick, Cheriaux, Olivier

A Subjective Evaluation Method for Sound Insulation of Vehicle Body in Reverberation Room and an Objective Prediction Model

2017-01-18866/5/2017

A subjective evaluation method for the air-borne sound insulation of vehicle body in reverberation room is developed and the correlation between the subjective preference and objective noise reduction level (NRL) is investigated in this paper. The stationary vehicle's interior noise is recorded by using a digital artificial head under a given white noise excitation in the reverberation room, which demonstrates more credible than those in traditional road test methods. The recorded noises of six different vehicles are replayed and evaluated subjectively by 22 appraisers in a sound quality room. The paired comparison scoring method is employed and the check and statistic methods for the subjective scores are introduced. The subjective preference is introduced and calculated by the statistics and normalization of the effective scores, which can indicate an overall preference ranking of all the six vehicles numerically. Furthermore, an objective prediction model is established based on the correlation analyses and linear regressions. The subjective preference is proved to be attributed to the average NRL in 2k-5kHz frequency range only. The subjective evaluation method and the prediction model provide the guidance for the evaluation, prediction, target setting and optimization of the vehicle sound insulation.

Zhang, Siwen, Pang, Jian, Zhang, Jun, Ma, Zhuangzhuang, Zhang, Xiaoxuan, Liu, Congguang, Deng, Lihui

Truck and Construction Seat BSR Identification and Characterization

2017-01-18586/5/2017

Truck and construction seats offer a number of different challenges compared to automotive seats in the identification and characterization of Buzz, Squeak, and Rattle (BSR) noises. These seats typically have a separate air or mechanical suspension and usually a larger number and variety of mechanical adjustments and isolators. Associated vibration excitation tend to have lower frequencies with larger amplitudes. In order to test these seats for both BSR and vibration isolation a low-noise shaker with the ability to test to a minimum frequency of 1 Hz was employed. Slowly swept sine excitation was used to visualize the seat mode shapes and identify nonlinearities at low frequencies. A sample set of seat BSR sounds are described in terms of time and frequency characteristics, then analyzed using sound quality metrics.

Haylett, James, Polte, Andrew

Continued Drive Signal Development for the Carbon Nanotube Thermoacoustic Loudspeaker Using Techniques Derived from the Hearing Aid Industry

2017-01-18956/5/2017

Compared to moving coil loudspeakers, carbon nanotube (CNT) loudspeakers are extremely lightweight and are capable of creating sound over a broad frequency range (1 Hz to 100 kHz). The thermoacoustic effect that allows for this non-vibrating sound source is naturally inefficient and nonlinear. Signal processing techniques are one option that may help counteract these concerns. Previous studies have evaluated a hybrid efficiency metric, the ratio of the sound pressure level at a single point to the input electrical power. True efficiency is the ratio of output acoustic power to the input electrical power. True efficiency data are presented for two new drive signal processing techniques borrowed from the hearing aid industry. Spectral envelope decimation of an AC signal operates in the frequency domain (FCAC) and dynamic linear frequency compression of an AC signal operates in the time domain (TCAC). Each type of processing affects the true efficiency differently. Using a 72 Wrms input signal, the measured efficiencies in the frequency range from 100 Hz to 10 kHz were 1.01 - 1083 E-6 and 1.26 - 388 E-6 percent for FCAC and TCAC, respectively. In addition, the effects of these processing techniques relative to sound quality were evaluated in terms of total harmonic distortion (THD). It was shown that although the different signal processing techniques affected the true efficiency, none of them increased the efficiency of the CNT loudspeaker to the level of current moving coil loudspeakers. Additionally, THD as the only sound quality metric is incomplete because these processing methods can be optimized for pure tones but highly distort complex signals like speech and music. Therefore, a sound quality metric for complex signals is needed. Overall, CNT loudspeakers show promise for specific applications where weight savings and complex geometries are required.

Bouman, Troy, Barnard, Andrew, Alexander, Joshua

A Systematic Approach to Engine Sound Design for Enhancing Sound Character by Active Sound Design

2017-01-17566/5/2017

This paper presents a systematic approach to interior engine sound design for enhancing sound character of car interior sound effectively. Nowadays an active noise control technology is widely used in vehicle industry. Particularly, an active sound design (ASD) technique using vehicle’s audio system for controlling interior sound due to powertrain has become a general method to improve sound quality or character. The ASD system using speakers has the advantage of creating various sounds relatively easy. In this study, the novel systematic approach is proposed to guide the efficient design of powerful and pleasant acceleration sound by order spectrum analysis. At first, primary attributes of powerful and pleasant sound were analyzed and sound concept was derived. Secondly, the optimal linearity and the level envelope of firing order were derived by subjective evaluation. Next, the engine orders arrangement was analyzed under the aspects of musical harmonic theory on six cylinders engine. The level ratio of harmonious orders for pleasant sound was also evaluated. And the novel powerful index based on booming and rumbling was developed and used for determining powerful sound target set-up. Finally, powerful and pleasant acceleration sound for six cylinders engine were suggested. These sounds have been implemented through the ASD.

Kim, Seonghyeon, Chang, Kyoung-Jin, Park, Dong Chul, Lee, Seung Min, Lee, Sang Kwon

A Novel Method for Objective Evaluation of Interior Sound in a Passenger Car and Its Application to the Design of Interior Sound in a Luxury Passenger Car

2017-01-17586/5/2017

Recently the interior sound is actively generated by the active sound design (ASD) device in a passenger car. Therefore, the objective evaluation method for the sound quality of actively designed sounds is required. In previous research, the sound quality of interior sound has been presented with powerful and pleasant for the existing passenger car. This paper presents a novel approach method for the objective evaluation of powerfulness and pleasantness of actively designed interior sound. The powerfulness has been evaluated based on the degreed of modulation and a quantity of low frequency booming of the sound in the paper. On the other hand, the pleasantness is evaluated based on the slope ratio of harmonic orders per octave in frequency domain. These evaluation methods are successfully applied to the objective evaluation of luxury passenger car. The sound with powerful and pleasant character is designed based on these two evaluation parameters and employed to the interior sound of a new luxury passenger car.

Lee, Seung Min, Park, Dong Chul, Kim, Seonghyeon, Lee, Sang Kwon

A Novel Method Predicting the Influence of Absorption Material on the Sound Quality of Interior Noise

2017-01-18856/5/2017

This paper presents a novel method predicting the variation of sound quality of interior noise depending on the change of the proprieties of absorption materials. At the first, the model predicting the interior noise corresponding to the change of the absorption material in engine room is proposed. Secondly the index to estimate the sound quality of the predicted sound is developed. Thirdly the experimental work has been conducted with seven different materials and validated the newly developed index. Finally, this index is applied for the optimization of absorption material to improve the sound quality of interior noise in a passenger car.

Lee, Kunhee, Lee, Sang Kwon, Shin, Taejin, Kim, Keun Young

Study for the Radiated Noise from Engine Depending on Assembly Condition

2017-01-18436/5/2017

This paper presents the influence of radiated noise from engine surface according to assembly condition between the engine block and oil pan. At the first, the force exciting the main bearing of cylinder block is calculated by using a multi-body dynamics model of the engine crankshaft. Secondly, the modal analysis is processed to obtain the mode contribution and modal participation factors for the FEM of a virtual cylinder block. Thirdly, the radiated noise from a structure is calculated by acoustic-FEM analysis. This structure is assembled by the virtual oil pan with a rigid connection method and a soft connection method. The sandwich panel connection model is used for the soft connection method. The sound radiated from this assemble structure is calculated according to two different connection properties respectively. The sound matrices for two results are compared using an objective method. Finally, the influence of the connection condition on the sound quality is investigated for the further research in a sound quality of the sound emitted by a real engine structure in a diesel engine.

Shin, Taejin, Jin, Jaemin, Lee, Sang Kwon, Jung, Insoo

Vibro-Impact Analysis of Manual Transmission Gear Rattle and Its Sound Quality Evaluation

2017-01-04033/28/2017

Experimental schemes, frequency characteristics, subjective and objective sound quality evaluation and sound quality prediction model establishment of a certain mass-production SUV (Sport Utility Vehicle, SUV) manual transmission gear rattle phenomenon were analyzed in this paper. Firstly, vehicle experiments, including experiment conditions, vibration acceleration sensor and microphone arrangements and especial considerations in experiments, were described in detail. Secondly, through time-frequency analysis, broadband characteristics of manual transmission gear rattle noise were identified and vibro-impact of gear rattle occurs in the frequency range of 450~4000Hz on the vehicle idle condition and the creeping condition. Thirdly, based on bandwidth filtering processing of gear rattle noise, subjective assessment experiments by a paired comparison method were carried out. Evaluation results passed triangular loop verification and Spearman correlation coefficient examination, and then subjective annoyance results of each noise sample were calculated. Further, objective evaluation results, based on two physical acoustics parameters and six psychological acoustics parameters, were obtained respectively. Finally, comprehensive evaluation of subjective and objective results was analyzed by the MLR (Multiple Linear Regression, MLR) method. It’s concluded that AI (Articulation Index) was the appropriate parameter that’s closely related to subjective annoyance results, and correlation coefficient of AI and subjective annoyance results was up to 0.948. Sound quality prediction model of gear rattle was then established on the vehicle idle condition and the creeping condition. Overall in this paper, research achievements could be adopted to solve practical engineering problems (especially gear rattle problem), and furthermore it could reduce R&D (Research and Design, R&D) cycle, labor costs and material costs dramatically.

Wu, Guangqiang, Wu, Huwei

Sound Quality Evaluation of Centralized Drive PMSM Based on Grade Scoring Method

2017-01-10613/28/2017

Electric vehicle driving permanent magnet synchronous motor has a wide speed range and load changes, with abundant harmonic currents, and its eccentric form is complex, which all result in poor sound quality and abnormal noise problems becoming increasingly prominent. To make a systematic and thorough study of the centralized drive permanent magnet synchronous motor (PMSM) is significant to ameliorate the sound quality and solve noise problems. MATLAB-based modeling technology, SPSS software, and the establishment of sound quality evaluation model for the centralized drive PMSM has a crucial reference value on the research and development of the electric vehicle driving permanent magnet synchronous motor. As for the sound quality of centralized drive PMSM, firstly, in order to get objective parameter values, evaluation models of objective parameters based on psychological acoustics should be established after the collection of the sound samples. Then, based on grade scoring method, the design of sound quality test and subjective evaluation test software are established to obtain subjective annoyance of these sound samples. Finally, after analyzing the correlation between subjective annoyance of the centralized drive PMSM and objective parameters, cubic regression models with regard to subjective annoyance with A-weighted sound level, loudness and speech intelligibility are also established respectively, in addition to a linear regression model of annoyance with these three parameters. Furthermore, after analyzing the correlation of objective parameters, speech intelligibility effects on subjective annoyance can be explained by the A-weighted sound level in large part. Meanwhile, an evaluation system for sound quality of centralized drive PMSM is implemented.

Zhai, Jiachen, Conggan, Ma

Sound Quality Rating of Passenger Car Diesel Powertrains

2017-26-01891/10/2017

The parameters such as lower noise levels, quietness, etc. of a vehicle has no longer remained the only driving features since the passenger car buyers are greatly influenced by the perception of the sound. In a scenario like this, the sound quality becomes of great importance especially for smaller diesel powertrains as they are more annoying than their gasoline counterparts. The idling noise is critical as its noise creates the first impression of the vehicle on the buyer. The Indian passenger car market is dominated by diesel cars equipped with smaller engines less than 2 liter capacity. Present work describes the methodology to formulate the equation for annoyance/pleasantness for the diesel powertrains used in Indian passenger cars. The index, Sound Annoyance Rating (SAR) developed through this work is significant for powertrain level target setting and benchmarking purposes. The sound data is recorded at powertrain level in hemi anechoic chamber at idling condition for 16 different powertrains with the capacity ranging from 1 lit-2 lit. Subjective evaluation is carried by combination of two jury evaluation techniques i.e., paired comparison method and percentage rated scale. About 80 subjects were involved in the evaluation of 16 powertrains. Analytical accuracy is improved by eliminating the outliers statistically. Psychoacoustic index (Loudness, Sharpness, Fluctuation Strength, Roughness, Articulation Index, etc) were calculated which forms the objective data. Analyses involves the identification of correlating metrics and further use multiple regression analysis where jury ratings are input as dependent variables and relevant sound quality metrics as independent variables to develop SAR index. The annoyance correlates with loudness, roughness, sharpness& fluctuation strength significantly. SAR is utilized to improve the sound quality of the test engine by modification of pilot injection strategy.

Mutalik, Keshav, A Gaikwad, Atul, Karanth, Nagesh Voderahobli, Chivate, Shriniwas

Sound Quality Evaluation of a Brake and Clutch Pedal Assembly used for Automotive Applications

2017-26-01941/10/2017

Sound Quality (SQ) of brake and clutch pedal assembly plays an important role in contributing to vehicle interior noise and perception of sound. Quiet operation of brake and clutch units also reflects the vehicle built and material quality. Noise emitted from these sub-assemblies has to meet certain acceptance criteria as per different OEM requirements. Not much work has been carried on this over the years to characterize and quantify the same. An attempt has been made in this paper to study the sound quality of brake and clutch pedal assemblies at component level and validate the same by identifying the parameters affecting SQ. Effect on noise at different environmental conditions was studied with typical operating cycles in a hemi-anechoic chamber. The effect of sensor switches integrated within the clutch and brake pedal on sound quality is analyzed. It is found that the operating characteristics of switches drives the noise and SQ. Wavelet analysis was carried out to correlate loudness sound quality metric with time-frequency amplitude modulations. Jury evaluation was performed to correlate subjective to objective data. Structural modifications were then suggested to improve the perception of sound. Significant improvement in the brake and clutch pedal assembly sound quality was achieved in product development with marginal impact on cost.

Rajamanickam, Ramkumar, Chivate, Shriniwas, Shinde, Gaurav, Karanth, Nagesh Voderahobli, Akre, Shalil, Desale, Kishor

Deconvolution Methods and Systems for the Mapping of Acoustic Sources from Phased Microphone Arrays

TBMG-261821/1/2017

NASA’s Langley Research Center researchers developed DAMAS using an iterative algorithm to deconvolute noise signals, allowing for more accurate quantification of the position and strength of acoustic sources. Recent development of the DAMAS microphone phased array processing methodology allows the determination and separation of coherent and incoherent noise source distributions. The DAMAS technology represents a significant breakthrough in the field of aero-acoustics.

Improvements to the Functional Beamforming Formula

TBMG-2600812/1/2016

The purpose of this work is to improve the signal-to-noise ratio of acoustic measurements made in a wind tunnel with a microphone phased array. The functional beamforming method is improved to compensate for effects of acoustic propagation through turbulence, and to correct for inaccurate steering vectors. This increases the accuracy with which acoustic measurements can be made in a non-acoustic or acoustic wind tunnel.

TOUCH TAKES HOLD, switches lend a hand

16OFHP10_0710/1/2016

Touch screens are becoming the norm, but knobs and switches are often used to improve operator comfort. System developers are leaving no technology unturned in their effort to boost performance by improving comfort. Touch screens dominate human-machine interface (HMI) development, but rotary knobs and push buttons remain relevant, as do joysticks, which could replace steering wheels. The electronic systems in cabs are evolving to meet expectations of operators used to the convenience of handheld electronics. However, evolving control strategies can't discount user's familiarity with knobs and buttons.

Costlow, Terry

Evaluation of Aircrew Noise Exposure Levels on a Canadian CH-147F Chinook Helicopter

F-0072-2016-11421

5/17/2016

The cabin and cockpit noise levels of a Royal Canadian Air Force CH-147F Chinook medium to heavy lift utility helicopter were evaluated in this study. The sound pressure levels were measured at nine aircrew locations through 43 unique and representative flight and ground conditions in accordance with the ISO 5129:2001 standard. Additionally, the performance of a combination of currently in service helmets and headsets were evaluated in accordance with the ANSI Standard S12.42. The hearing protection performance results were used in combination with the measured sound pressure levels to evaluate the performance of the hearing protection in the context of the CH-147F noise environment. Results showed that the David Clark headsets equipped with active noise reduction provided the most superior hearing protection. The maximum exposure limit duration was calculated for each microphone location, hearing protector performance and flight condition combination. It was found that the David Clark headsets provided sufficient protection for an unlimited duration of exposure for an individual with a properly fitted headset. It was also found that improperly fitted hearing protection could result in an increased risk of hearing damage after merely 18 seconds.

Price, Andrew, Ghinet, Sebastian, Chen, Yong, Wickramasinghe, Viresh, Grewal, Anant