Browse Topic: Acoustics
ABSTRACT Curtiss-Wright has developed an acoustic based sensor technology for measuring friction, shock, and dynamic load transfer between moving parts in machinery. This technology provides a means of detecting and analyzing machine structure borne ultrasonic frequency sounds caused by friction and shock events between the moving parts of the machine. Electrical signals from the sensors are amplified and filtered to remove unwanted low frequency vibration energy. The resulting data is analyzed as a computed stress wave energy value that considers the amplitude, shape, duration and rates of all friction and shock events that occur during a reference time interval. The ability to separate stress waves from the lower frequency operational noise makes this technology capable of detecting damaged gears/bearings and changes in lubrication in equipment earlier than other techniques, and before failure progression increases cost of repair. Already TRL9 in adjacent industries, this technology
Vehicle HVAC noise performance is an important vehicle design validation criterion since it significantly links the brand image of a vehicle. It affects the customer’s buying decision and the business of selling vehicles because it directly affects driving comfort. Customers expect continuous improvement in HVAC noise without compromising cooling performance. The process of cascading vehicle-level acoustic performance to subsystem and component levels becomes an important factor in the vehicle NVH development process. It was found that the component-level [HVAC unit without duct] performance of an HVAC system measured in an anechoic chamber was at par when compared to targets, whereas the subsystem-level performance [HVAC unit with duct and dashboard] was on the higher side of the targets. Advanced NVH tools were used to identify the source of noise at the subsystem level. It helped to locate the source and its transfer path. A design modification done at the transfer path location
When traveling in an open-jet wind tunnel, the path of an acoustic wave is affected by the flow causing a shift of source positions in acoustical maps of phased arrays outside the flow. The well-known approach of Amiet attempts to correct for this effect by computing travel times between microphones and map points based on the assumption that the boundary layer of the flow, the so-called shear layer, is infinitely thin and refracts the acoustical ray in a conceptually analogy to optics. However, in reality, the turbulent nature of both the not-so-thin shear layer and the acoustic emission process itself causes an additional smearing of sources in acoustic maps, which in turn causes deconvolution methods based on these maps – the most prominent example being CLEAN-SC – to produce certain ring effects, so-called halos, around sources. In this paper, we intend to cast some light on this effect by describing our path of analyzing/circumventing these halos and how they are linked to the
Design verification and quality control of automotive components require the analysis of the source location of ultra-short sound events, for instance the engaging event of an electromechanical clutch or the clicking noise of the aluminium frame of a passenger car seat under vibration. State-of-the-art acoustic cameras allow for a frame rate of about 100 acoustic images per second. Considering that most of the sound events introduced above can be far less than 10ms, an acoustic image generated at this rate resembles an hard-to-interpret overlay of multiple sources on the structure under test along with reflections from the surrounding test environment. This contribution introduces a novel method for visualizing impulse-like sound emissions from automotive components at 10x the frame rate of traditional acoustic cameras. A time resolution of less than 1ms eventually allows for the true localization of the initial and subsequent sound events as well as a clear separation of direct from
From a Noise Vibration Harshness (NVH) perspective, electric vehicles represent a great opportunity since the noise of the combustion engine, dominant in many driving conditions, is no longer present. On the other hand, drivers accustomed to driving cars with a strong personality (for example typically sporty ones) may perceive "silence" as a lack of character. Our internal study, conducted with a jury of people, has in fact already shown that for half of customers silence should characterize (Battery Electric Vehicle - BEV) vehicle; but, at the same time, the other half of the jury expects feedback from the vehicle while driving. The silence inside the passenger compartment, from an NVH point of view, can therefore be compared to a blank sheet of paper, on which, if desired, sounds designed to satisfy the driving pleasure expected by the customer can be introduced. Starting from this scenario, the paper describes: the approach adopted to define how many and what are the levers to
As palliative acoustic material mixtures and compositions become more complex, the ability to accurately simulate their acoustic performance within an installed NVH component is becoming increasingly difficult. Historically, Biot parameters and their associated TMM models have been used to simulate the acoustic performance of multi-layered material compositions. However, these simulations are not able to account for real-world complexities such as manufacturing imperfections or inter-layer gluing effects. The assumptions made by simulation models, such as the perfectly diffuse field, are rarely true in actual measurements, let alone in the vehicle, further increasing the uncertainty when comparing measurement versus simulation. There already exists widely accepted methods for obtaining Biot parameters for single-layer materials. Typically, a multi-layer simulation considers each individual layer in isolation rather than its interactions with the rest of the composition after heating
In the acoustic study of the interior noise of a vehicle, whether for structure-borne or air-borne excitations, knowing which areas contribute the most to interior noise and therefore should be treated as a priority, is the main goal of the engineer in charge of the NVH. Very often these areas are numerous, located in different regions of the vehicle and contribute at different frequencies to the overall sound pressure level. This has led to the development of several “Panel Contribution Analysis” (PCA) experimental techniques. For example, a well-known technique is the masking technique, which consists of applying a “maximum package” (i.e., a package with very high sound insulation) to the panels outside of the area whose contribution must be measured. This technique is pragmatic but rather cumbersome to implement. In addition, it significantly modifies the dynamics and internal acoustics of the vehicle. In another well-known technique, the contribution of a certain area is defined
The development of an effective Acoustic Vehicle Alerting System (AVAS) is not solely about adhering to safety regulations; it also involves crafting an auditory experience that aligns with the expectations of vulnerable road users. To achieve this, a deep understanding of the acoustic transfer function is essential, as it defines the relationship between the sound emitter (the speaker inside the vehicle) and the receiver (the vulnerable road user). Maintaining the constancy of this acoustic transfer function is paramount, as it ensures that the sound emitted by the vehicle aligns with the intended safety cues and brand identity that is defined by the car manufacturer. In this research paper, three distinct methodologies for calculating the acoustic transfer function are presented: the classical Boundary Element method, the H-Matrix BEM accelerated method, and the Ray Tracing method. Furthermore, the paper encompasses an assessment of the correlation between these methods and their
One of the five major performances of vehicles, NVH(Noise, Vibration, Harshness), has recently emerged in electric vehicles, again. And, front loading NVH simulation is essential to respond nimbly to automotive industry these days. However, the two components of the simulation, mathematical sound absorption modeling equation, and the acoustic parameters, the input factor, is requiring improvement because of lack of robustness. In this study, we tried to strengthen, standardize, and refine the connectivity between micro (fine structure) and macro (acoustic parameter-related physical properties) characteristics, and improve the consistency with actual NVH performance. As a porous polymer material, polyurethane foam, which is widely used for the interior and exterior of automobiles, is treated as a target material. It is expected that further refining of the correlation between three-dimensional microstructure properties of foam such as pore, throat, strut, window, etc. and acoustic
This research looks at the acoustic and mechanical characteristics of polypropylene (PP) composites supplemented with natural fibers to determine whether they are appropriate for automotive use. To generate composites that are hybrids, four diverse natural fibers, including Calotropis gigantea (CGF), jute, sisal, and kenaf, were mixed into PP matrices. The study examines how fiber type, frequency, and thickness affect sound absorption and mechanical strength. The results show that these natural fiber-reinforced composites have improved mechanical characteristics, with CGF (73.26 shore D value of Hardness), sisal (42.35 MPa tensile) and jute fibers showing particularly promising materials. Furthermore, the acoustic study emphasizes these materials’ frequency-dependent sound absorption properties, with particular efficacy in mid-frequency regions. Such organic reinforcement fiber materials’ acoustic performance is tested at 5 mm and 10 mm thicknesses. When a 5 mm thick sample is examined
Customer preference towards quieter vehicles is ever-increasing. Exhaust tailpipe noise is one of the major contributors to in-cab noise and pass-by-noise of the vehicle. This research proposes a silencer with an integrated acoustic valve to reduce exhaust tailpipe noise. Incident exhaust wave coming from the engine strikes the acoustic valve and generates reflected waves. Incident waves and reflected waves cancel out each other which results in energy loss of the exhaust gas. This loss of energy results in reduced noise at the exhaust tailpipe end. To evaluate the effectiveness of the proposed silencer on the vehicle, NVH (Noise, vibration, and harshness) performance of the proposed silencer was compared with the existing silencer which is without an acoustic valve. A CNG (Compressed natural gas) Bus powered by a six-in-line cylinder engine was chosen for the NVH testing. After NVH evaluation, it was found that when using the proposed silencer, overall exhaust tailpipe orifice noise
A cutting-edge technology known as acoustic touch helps people see using sound. The technology has the potential to transform the lives of those who are blind or have low vision. The next-generation smart glasses translate visual information into distinct sound icons
In this study, a novel assessment approach of in-vehicle speech intelligibility is presented using psychometric curves. Speech recognition performance scores were modeled at an individual listener level for a set of speech recognition data previously collected under a variety of in-vehicle listening scenarios. The model coupled an objective metric of binaural speech intelligibility (i.e., the acoustic factors) with a psychometric curve indicating the listener’s speech recognition efficiency (i.e., the listener factors). In separate analyses, two objective metrics were used with one designed to capture spatial release from masking and the other designed to capture binaural loudness. The proposed approach is in contrast to the traditional approach of relying on the speech recognition threshold, the speech level at 50% recognition performance averaged across listeners, as the metric for in-vehicle speech intelligibility. Results from the presented analyses suggest the importance of
As the vehicle electrification progresses and the demand for acoustic comfort increases, the NVH performance of brakes becomes more important theme. In-plane squeal of disc brake is one of phenomena that is difficult to countermeasure. In this study, we used array microphones to search for sound sources of in-plane squeal in order to elucidate the mechanism. The Microphones were set in the out-of-plane direction and the lateral direction of a disc in brake components on a full-sized dynamometer. In the vibration mode in which in-plane stretch vibration was dominant, the sparse and dense parts showed high sound pressure. 3D laser vibrometer was used to check displacements of the disc, and the result indicated a possibility that the sparse and dense parts could vibrate in the out-of-plane direction and generate the sound. Then, complex eigenvalue analysis (CEA) and acoustic simulation were conducted to validate the experimental results. Firstly, frequency of instability mode occurred in
A team of researchers from Heidelberg University and Max Planck Institute for Medical Research have created a new technology to assemble matter in 3D. Their concept uses multiple acoustic holograms to generate pressure fields with which solid particles, gel beads, and even biological cells can be printed. These results pave the way for novel 3D cell culture techniques with applications in biomedical engineering
General Atomics Aeronautical Systems Inc. Poway, CA (858) 312-2810
Electrification brings new benchmarks, tools, and challenges to the ongoing battle with noise, vibration and harshness. The complex science of analyzing and abating noise, vibration, and harshness has entered a “new frontier” as the industry transitions to electrified vehicles, experts in the NVH field tell SAE Media. New design and engineering challenges at the component, system, and full-vehicle levels continue to emerge as EV offerings expand beyond the initial wave of predominantly premium-spec products. Engineers note that benchmarking activity and the introduction of new analysis and testing tools related to NVH mitigation are at “crazy” levels. “Our interest in acoustically improved vehicles always is going to accelerate and the NVH technology must always meet customer expectations,” observed Pranab Saha, whose company Kolana & Saha Engineers in Waterford, Mich., specializes in acoustics, noise and vibration analysis and testing. He noted that some of the latest EV designs show
Pass-by noise measurement is mandatory for automotive manufacturers for conformity of production. With evolving of pass-by noise requirements (under 68 dB in 2024), all the stakeholders should be able to comply with this criterion. OEMs, suppliers of passive acoustic treatments, road manufacturers and tire manufacturers are concerned and should deploy efforts to provide solutions for control of exterior noise. In this regard, simulations are preferable over measurement campaigns as they can provide fast feedback on passive exterior treatments for exterior noise control. In the particular case of Lightyear vehicles, the main contributors to pass-by noise are tires and in-wheel motors. Considering that, a contribution of each of these two sources of noise to pass-by noise will be described. Tire noise sources and motor noise sources will be replaced by simple monopole sources. The best monopole source location for both tires and motors is discussed. Actran vibro-acoustic Finite Element
The transport refrigeration market is in a transformation like what automotive experienced over the last 20 years using a systems engineering approach complemented with complex attribute optimization to manage product development. With a heavy push for electrification due to government regulations, sustainability initiatives, and designing the products to align with the OEMs electrified platforms Noise, Vibration, and Harshness (NVH) must be considered. Understanding the above along with refined customer expectations the NVH attribute has become even more critical to product quality. This paper showcases the acoustic design of an electrified system using a system engineering approach to achieve unit level targets deploying a system engineering V-model philosophy. Unit level requirements were set and flowed down to component level requirements. A 1D acoustic tool was developed leveraging classic physical acoustics theory and legacy product knowledge to target set what was possible for
This contribution describes a novel method for visualizing leakages in automotive structures using a rotating linear array of a few digital ultrasound microphones in combination with a multi-frequency ultrasound transmitter. The rotating array scans the incident sound field generated by the ultrasound transmitter on a circular area. In a typical measurement setup, the ultrasound transmitter is placed in a cavity (e.g. car interior, trunk or similar) and operates at distinct harmonic frequencies at around 40kHz in an omnidirectional fashion. The rotating linear array is operated on the outside of the cavity and captures the sound field escaping through small leakages. While the reduced hardware complexity allows for the design of a lightweight, handheld sound imaging device, the algorithmic portion of the measurement system requires special attention. In fact, established methods of sound imaging like beamforming and nearfield holography cannot be applied to signals stemming from moving
Traditionally vehicles are designed for wind noise under ideal steady wind conditions. But, passenger comfort is affected by high modulation of cabin noise while cruising in traffic due to variations of instantaneous wind speed and direction from driving through large-scale turbulence. In consequence, designing a vehicle for the best performance in a low-turbulence wind tunnel may lead to issues during on-road conditions. To predict the interior noise corresponding to on-road turbulence, a simulation approach is proposed combining an upstream turbulence flow simulation with an SEA vehicle model. This work is an extension of existing well validated procedures for steady wind conditions. Time-segmented transient loads on panels and steady-state structural acoustics transfer functions are combined, producing interior noise results for a series of overlapping time segments. This interior noise prediction, as a function of time, captures the modulation of wind noise results, which are then
Speaker performance in Acoustic Vehicle Alerting System (AVAS) plays a crucial role for pedestrian safety. Sound radiation from AVAS speaker has obvious directivity pattern. Considering this feature is critical for accurately simulating the exterior sound field of electrical vehicles. This paper proposes a new process to characterize the sound directivity pattern of AVAS speaker. The first step of the process is to perform an acoustic testing to measure the sound pressure radiated from the speaker at a certain number of microphone locations in a free field environment. Based on the geometry of a virtual speaker, the locations of each microphone and measured sound pressure data, an inverse method, namely the inverse pellicular analysis, is adopted to recover a set of vibration pattern of the virtual speaker surface. The recovered surface vibration pattern can then be incorporated in the full vehicle numerical model as an excitation for simulating the exterior sound field. In this study
In the current changing noise, vibration, and harshness (NVH) landscape, there is an increased amount of collaboration between NVH engineers and other attribute engineering groups to solve complex issues. One of these complex issues is ride comfort. An increasing amount of ride comfort development is happening between NVH and ride and handling (R&H) engineers. To apply a NVH process to a R&H phenomenon, it is important to ensure that both the transducer selection as well as analysis method will be applicable over the frequency range of interest. Specifically for ride comfort development, the validation of the use of strain gauges and accelerometers along with source path contribution analysis, or transfer path analysis, is key to bridging the gap between NVH and R&H. A source path contribution, also known as a transfer path analysis, model can be utilized to understand the contributions from various sources, both structural and acoustic, to a given set of receivers in the interior of a
Helmholtz resonator is a very common anechoic measure, and it is widely used in pipe acoustic fields. Based on the enlightenment of the classic Helmholtz resonator, this paper proposes a headrest resonator model and extends it to the acoustic field of the passenger cabin to improve the road noise in the car. Firstly, through the theoretical model of Helmholtz resonator, the relationship between its resonance frequency and the geometric size of the resonator is clarified. Secondly, the influence of the headrest resonator on the acoustic field characteristics of the car is studied through finite element simulation analysis. It is demonstrated that the headrest resonator is placed in the car, and the sound pressure distribution characteristics of the passenger's inner ear near the resonance frequency change significantly. At the same time, through 3D printing, a sample of the headrest resonator is made. In addition, the acoustic test of the passenger cabin-headrest resonator coupling
In the context of automotive air boosting systems, such as turbochargers and full-cell compressors, earlier and more realistic noise evaluations are crucial in evaluating the impact a design has on the final acoustic performance perceived by the end user in the vehicle cabin environment. This requires a combined assessment of the acoustic sources from boosting systems, other vehicle interior noise sources, and the acoustic transfer path from the boosting system to the vehicle cabin. Performing such an assessment experimentally cannot be done early in development with representative hardware and can be expensive. Also, managing such an assessment entirely through simulations is very complex and error prone. The present study proposes a hybrid approach to tackle this noise challenge. This methodology combines the noises of high-speed rotating machine simulated rotor-dynamic and electromagnetic simulation processes, their transformation from frequency to time domain, and coupling with
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