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08.04 Vehicle Sound Design & Simulation

Design and simulation of Helmholtz resonator assembly used to attenuate tire acoustic cavity resonance noise
Time: 8:40 pm

Author: Wei Zhao

Abstract ID: 1706

Tire acoustic cavity resonance noise (TACRN) is a typical annoying lower-frequency interior noise of a passenger car. The widely used attenuating method of attaching the porous sound absorption material in tire cavity can reduce TACRN effectively, but causes the increase of tire-wheel assembly weight and cost, also the poor durability. Additionally, the Helmholtz resonator (HR) is also used in the wheel of some cars although having only narrow effective band. The existing investigation shows that the frequency of TACRN varies with the car speed and load and also has the split characteristics. The change of TACRN frequency causes a certain difficulty to suppress TACRN effectively. Aiming at this problem, in this paper, TACRN frequency range of a specific tire cavity under different operating conditions is first calculated and analyzed. Then, for a specific aluminum alloy wheel, a HR assembly including several HRs is designed to make the natural frequencies of HR assembly cover the TACRN frequencies. Finally, the reduction effect of TACRN is simulated and evaluated by comparing the sound fields in tire cavity with/without HR assembly under same volume velocity sound source. This work is helpful for attenuating TACRN effectively under the changing operating conditions.

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Simulation of the frequency split of the fundamental air cavity mode of a loaded and rolling tire by using steady-state transport analysis
Time: 8:00 pm

Author: Won Hong Choi

Abstract ID: 2889

It has been found that when a tire deforms due to loading, the fundamental air cavity mode splits into two due to the break in geometrical symmetry. The result is the creation of fore-aft and vertical acoustic modes near 200 Hz for typical passenger car tires. When those modes couple with structural, circumferential modes having similar natural frequencies, the oscillatory force transmitted to the suspension can be expected to increase, hence causing increased interior noise levels. Further, when the tire rotates, the frequency split is enlarged owing to the Doppler effect resulting from the airflow within the tire cavity. The current research is focused on determining the influence of rotation speed on the frequency split by using FE simulation. In particular, the analysis was performed by using steady-state transport analysis which enables vibroacoustic analysis in a moving frame attached to tire in the frequency domain. The details of the modeling are described and results are given for a tire under different rotation speeds, presented in terms of dispersion curves that illustrate the interaction between structural and acoustical modes. The results are compared to those for static tires and tires spinning without translational velocity to highlight the effects of rolling.

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Experimental Observations in Tire Cavity Resonance and Interactions with Periodic Noise Components
Time: 7:40 pm

Author: Jordan Schimmoeller

Abstract ID: 3224

Tire cavity resonance is one of the major sources of tire-related in-cabin noise and vibration. It has gained more attention in recent years with the growth of the electric vehicle market. This is due to the absence of masking noise from the internal combustion engine and powertrain. Thus, the mitigation of this issue has become a critical task for tire and vehicle manufacturers. The excited cavity resonant frequency in an unloaded condition is typically between 170 – 220 Hz. However, multiple studies have shown that loading the tire will result in two dominant resonances transmitted into the cavity. Their corresponding mode shapes are typically described in terms of the direction of their characteristic acoustic pressure variation i.e., fore-aft cavity mode and vertical cavity mode. As the tire’s rotational speed increases, in-cabin measurements show that the tire cavity resonant frequencies separate from each other. Further, interactions with the periodic component of tire noise at certain speeds are also observed. These periodic components can be attributed to tire non-uniformities and tread pattern related excitation. This interaction is perceived as tonal noise inside the vehicle cabin at discrete speeds. This work presents experimental results summarizing these findings.

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Design of an In-cabin Personal Audio Zone System Using an Optimized Acoustic-Contrast-Control-Pressure-Matching Algorithm
Time: 7:00 am

Author: Zhe Zhang

Abstract ID: 1805

This paper presents the design of an in-cabin personal audio zone (PAZ) system that enables the driver and one rear-row passenger to listen to different audio programs with acceptable mutual disturbance. The system is designed predicated on a modified acoustic-contrast-control-pressure-matching (ACC-PM) algorithm, which is optimized using the genetic algorithm (GA) to find out the optimum tradeoff between performance indices including the acoustic contrast (AC) and error performance (Err) and the numerical stability of the algorithm. Comparison with the traditional ACC-PM algorithm reveals an increased contrast and improved reproduction quality. In addition, perhaps more importantly, the numerical stability of the optimized algorithm is substantially enhanced, making it possible to involve more loudspeakers into the PAZ system to achieve an even better sound compartmentalization performance.

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Suggestive Sound Design – How to use Active Interior Sound Design to improve traffic safety
Time: 7:40 am

Author: Manuel Petersen

Abstract ID: 1874

Active sound design becomes an important addition to the newest generation of premium class electrical vehicles to enhance the emotionality of the driving experience. Musicological research indicates that emotions are altered by certain harmonic sets of pitches, whereas results in traffic psychology show that emotions can influence the driving behavior. Despite these findings, there is no research done on how changes to an active vehicle sound could influence the driving behavior. In this paper, we describe an approach for a suggestive sound design. It’s based on the hypothesis, that the chosen safety distance by a driver could be altered by changing the inherent dissonance of an active interior vehicle sound based on the current safety distance. The suggestive sound design is based on an additive synthesizer utilizing the Shepard-Risset glissando. The sound can be controlled by external signals e.g. CAN signals from real or virtual vehicles. To verify this hypothesis, a driving simulator was built in which the driving experience with a suggestive sound and the resulting driving behavior can be validated through subject studies within an immersive and reproducible virtual reality environment. The research aims at improving road safety by influencing the driver through changes in the interior vehicle sound.

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Acceleration sound design for vehicles using distortion products
Time: 6:20 am

Author: Yu Aburagi

Abstract ID: 2154

When considering the acoustic design of automobiles, low-frequency sounds can increase the excitement levels for users. However, there are several problems accompany an increase in the low-frequency levels of an engine sound. For example, it is difficult to create a balance between silence and excitement when a sound’s different order components are changed. It is also difficult to generate heavy bass engine sounds in practical scenarios. Thus, the application of distortion products in the auditory system of the cochlea is considered. Distortion products are perceived when two or more sounds with slightly different frequencies are played simultaneously. This study was conducted to examine the possibility of achieving powerful engine sounds using distortion products. At first, the relationship between different combinations of complex sounds and the pitch perception of distortion products was investigated. As a second step, the application of distortion products to the acceleration sound was also considered. The results suggested the possibility of synthesizing a low-frequency component using distortion products inside a cochlea.

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Auralization of electric vehicle’s interior noise SEA simulation
Time: 6:00 am

Author: Eunsoo Jo

Abstract ID: 2250

Statistical Energy Analysis (SEA) has become an essential step to minimize the vehicle interior noise level. The outcome of SEA is typically 1/3 octave spectrum, and consequently it is difficult to understand the subjective effect of interior noise. This study investigated two approaches to achieve the binaural synthesis of SEA results. One is directly from the SEA 1/3 octave result and the measured coherence function. The other makes use of Source Path Contribution (SPC) to estimate the time signals on the exterior panels and subsequently applies the SEA results as a set of Finite Impulse Response (FIR) functions. Both approaches seem to result in realistic binaural signals as well as the correctly scaled sound pressure levels at the receivers. The one using SPC results can generate the input data for an NVH driving simulator by decomposing the harmonics and the masking noises. This means that the SEA result can be experienced by driving the simulated vehicle freely.

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An analytical model for predicting noise radiated by switch reluctance electric motors
Time: 8:00 am

Author: BAHADIR SARIKAYA

Abstract ID: 2601

Switch reluctance motors (SRM) have become a prominent alternative for electric vehicles in recent years due to their simple, high power density architecture and cost-effective manufacturability. Despite its potential, NVH problems have been one of the biggest challenges for SRM’s implementation. Vibration and noise generated by the SRM are mainly caused by phase switching related torque ripple, unbalanced electromagnetic forces from air gap variations and lamination problems. Our proposed model is an analytical noise radiation prediction model which relates geometrical, material and electrical design inputs to radiated sound power. The electromagnetic part of the model is nonlinear with saturation and provides back-emf and flux linkage by receiving design inputs. The computed magnetic energy, radial and tangential rotor forces are utilized as excitation sources to a continuous shell dynamic model to obtain the steady-state vibration response. Finally, surface velocities obtained from the shell model are used to calculate sound power. Utilizing a shell structure provides axial, radial and tangential information on the casing by considering the effect of magneto-restrictive forces of laminations, torque ripples and unbalanced electromagnetic forces. The effect of air gap, lamination error, and stator and rotor geometry on sound radiation are studied through an example case study.

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A dynamic shell model for diagnostics of rotating machinery under periodic excitation
Time: 8:20 am

Author: Murat Inalpolat

Abstract ID: 2605

In this paper, a generalized dynamic model of a shell structure has been developed and utilized for diagnostics purposes. The dynamic model is three-dimensional, includes the effects of rotary inertia and shear deformation, and can handle moving loads in radial, tangential and axial directions. The model is utilized to determine in-plane radial displacements of the shell structure under concentrated radial loads for different boundary conditions. The periodic loads are constructed using harmonics obtained through the Fourier series expansion method. The modal expansion technique is implemented for calculation of the steady state forced response of the shell structure. A simplified acoustic radiation model is also implemented in conjunction with the dynamic shell model to predict the noise radiated from a rotating circular cylindrical shell structure under different kinematic, loading and boundary conditions. Moreover, forced vibration response and acoustic radiation predicted will be employed to reveal patterns in the signals that can potentially be used for diagnostics of rotating machinery applications. The shell model is derived using a comprehensive approach and thus can be used to model prevalent engineering applications ranging from electric motors to gears and bearings.

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Perceptual Difference on HVAC Sound Quality between Electric and Conventional Vehicles
Time: 6:40 am

Author: Katsuya Yamauchi

Abstract ID: 2629

The heating, ventilation and air-conditioning (HVAC) system is one of the most critical sources in in-vehicle noise environment, especially when cars are moving at low speed or at lower engine rotation. With the transition to electric vehicles (EV) from internal combustion engine vehicles (ICEV), the contribution of powertrain becomes lower on the background noise inside car cabins. The authors have been conducting a collaborative research on HVAC sound quality inside car cabins. In this paper the results of a subjective evaluation of HVAC sound quality were presented, that attempted to compare the perceptual differences among the two groups, i.e. EVs and ICEVs. The result revealed the difference in the noise perception among the two types of vehicles especially softer air flow rate conditions.

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