車輛總工程師并不滿意他在最近一次試駕中聽到的車內(nèi)的噪聲。
他原本正在仔細(xì)復(fù)核一款新的變速箱，并打算把它用在公司最具競(jìng)爭(zhēng)力的跑車系列上。然而，當(dāng)車搭載上這款變速器后，車內(nèi)產(chǎn)生了很大噪音，效果令人難以接受。對(duì)此，首席工程師顯然很不滿意，而據(jù)設(shè)計(jì)師和制造工程師解釋，這款新的變速箱的最大特色就是其纖薄輕巧的鋁制外殼。然而，這款輕巧的外殼正是制造出巨大噪音的“罪魁禍?zhǔn)?rdquo;。
公司已經(jīng)投入資金做了這個(gè)部件的預(yù)定，項(xiàng)目截止日期也不斷逼近，一通電話被撥到了Pranab Saha的辦公室。
“他們請(qǐng)我?guī)退麄冊(cè)O(shè)計(jì)一個(gè)解決方案，”Saha這么說道。Saha是密歇根州 Waterford 地區(qū)咨詢公司 Kolano & Saha 的注冊(cè)噪聲控制工程師、聲學(xué)專家。他告訴我們，一開始，由于鋁箔襯背絕緣材料的緣故，這款變速箱的噪音問題得以掩蓋。然而，這塊絕緣材料上必須開幾個(gè)孔，這樣才能不影響連接和布線。而問題就在于這些切口會(huì)給噪聲的傳播制造通道。
對(duì)此，Saha的解決方案是：與其在變速器外殼采用絕緣材料，不如將絕緣材料放在變速器通道下方。工程師將重新審視自己的 CAD 圖紙?jiān)O(shè)計(jì)，并進(jìn)行相應(yīng)的修改。接下來，他們將進(jìn)行噪聲分析，驗(yàn)證新解決方案的有效性。
Saha指出，“這只是我們幫客戶解決噪聲問題的案例之一：該從哪里入手優(yōu)化 NVH 性能呢？”
目前，分析、衰減和消除車輛 NVH 影響，已經(jīng)成為汽車研發(fā)中不可分割的一部分。NVH 工程團(tuán)隊(duì)正在開展“每天降噪一分貝”的項(xiàng)目，要像降低車輛重量或提高車輛燃料經(jīng)濟(jì)性一樣，努力降低車艙內(nèi)的噪聲。
“噪音和震動(dòng)（N&V）這個(gè)領(lǐng)域很特殊，因?yàn)樗陌l(fā)展原動(dòng)力來自于市場(chǎng)競(jìng)爭(zhēng)，而非政府規(guī)定，”Saha解釋道，“如今，我們會(huì)聽到有些OEM吹噓，說自己某款車的車內(nèi)聲效比市面上的某一款好，噪音也更小。而隨著汽缸鈍化、混合動(dòng)力以及電動(dòng)汽車等技術(shù)被引入市場(chǎng)，降噪減震會(huì)變得愈發(fā)重要。”
Cooper-Standard全球產(chǎn)品戰(zhàn)略副總裁兼防震系統(tǒng)開發(fā)組主管Joe Emmi告訴我們，隨著自動(dòng)駕駛汽車所搭載的全新人機(jī)交互界面（HMI）走向市場(chǎng)，車廂更安靜和駕車更平順已經(jīng)成為了人們的一種訴求。
目前，OEMs和一級(jí)供應(yīng)商已經(jīng)投入了數(shù)十億資金，用于開發(fā)新的 NVH 軟件、設(shè)施、材料及支付 Saha 等其他聲學(xué)專家咨詢公司的咨詢費(fèi)。此外，吸音材料對(duì)保證車輛的 NVH 性能非常關(guān)鍵，因此吸音材料制造商的發(fā)展也邁入上升趨勢(shì)。根據(jù) 2017 年《大觀研究》(Grand View Research) 報(bào)告，2021 年之前，消聲產(chǎn)品的全球市場(chǎng)規(guī)模的年均復(fù)合增長(zhǎng)率將達(dá) 6%，在 2021 年達(dá)到 135.2 億美元。
在此背景之下，聰明的供應(yīng)商也開始順應(yīng)市場(chǎng)趨勢(shì)，推銷自己的消聲材料，比如：Material Sciences Corp. 用于儀表盤的“無聲鋼（Quiet Steel）”，日企Technol Polymer Co. Ltd的“Hushlloy”熱塑性消聲塑料，以及Sika Automotive公司可用于抑制車身共振的共擠型合成橡膠“Sika Damp”。
此外，為了響應(yīng)汽車行業(yè)對(duì) NVH 性能的重視，市場(chǎng)中還涌現(xiàn)了一批專用NVH 性能優(yōu)化軟件，包括：SCS 公司的 V-Path 傳播路徑分析軟件；HEAD Acoustics 公司的 Artemis NVH 測(cè)試軟件；Genesis 公司的 LEA；Altair Engineering 公司的 HyperWorks 套裝，及達(dá)索系統(tǒng) CATIA V6/3DS 內(nèi)的嵌入式NVH 工具箱及Siemens PLM 等等。
SAE International一直以來都致力于為NVH工程師提供一個(gè)專業(yè)的交流、溝通的平臺(tái)，學(xué)會(huì)每?jī)赡昱e辦一次（今年會(huì)議與展覽將在密歇根州的Grand Rapids地區(qū)舉辦）的“噪音與震動(dòng)技術(shù)大會(huì)與展覽（Noise and Vibration Conference and Exhibition）”。
“控制變量法”
N&V工程師研究的領(lǐng)域包含了信息源、路徑（包括實(shí)體架構(gòu)和空氣）和接收器（即噪音和震動(dòng)的目標(biāo)物）。這個(gè)領(lǐng)域中，越早確定問題所在并著手解決，成功的可能就越大。在一定程度主觀判斷的基礎(chǔ)之上，這些工程師把重點(diǎn)放在量化目標(biāo)參數(shù)之間的關(guān)系上，比如：通過某種數(shù)據(jù)獲取方式精確比對(duì)聲音和頻率的測(cè)量值。
終端客戶輸入也是分析的一部分。對(duì)于很多客戶而言，提高音效和減少噪音及降低其分貝同樣重要。心理聲學(xué)專家對(duì)此十分認(rèn)同。聲音的音量、刺耳度和清晰度指數(shù)（一種在噪音環(huán)境下聆聽講話的清晰度測(cè)試）都是主觀參數(shù)。
接受本文采訪的專家都認(rèn)同說，與鋼結(jié)構(gòu)相比，輕薄的鋁結(jié)構(gòu)在眾數(shù)分析中會(huì)展現(xiàn)出更多不同的N&V特性，并且有不少特性令專家相當(dāng)犯難。要控制好震動(dòng)就需要更結(jié)實(shí)的車身面板和附加的抑制材料，如LASD底部填補(bǔ)劑和洞孔填充泡沫。
有些應(yīng)用程序采用了主動(dòng)降噪系統(tǒng)（詳見Honda補(bǔ)充報(bào)道，將于近期即將在微信平臺(tái)推送）。這類應(yīng)對(duì)方案常被冠以“創(chuàng)可貼”的稱呼，原因就在于它們并不直擊問題根源——也就是基本設(shè)計(jì)框架的問題，比如：氣缸體諧振過度等結(jié)構(gòu)性問題。此外，這種解決方案還會(huì)增加車身重量。
Altair Engineering汽車部的高級(jí)副總裁Richard Yen觀察后指出，“很多公司在NVH方面都做得不錯(cuò)，但它們的根本問題是總要等到汽車研發(fā)的尾聲階段才進(jìn)行各種測(cè)試。也就是說他們把大量的錢花在了糾錯(cuò)上。”
如果選擇使用鋁制材料，工程師往往會(huì)添加更多用料，以達(dá)到和鋼結(jié)構(gòu)同樣的降噪減震效果。在NVH專家Saha看來，這樣做的結(jié)果就是“實(shí)際上在汽車內(nèi)部‘購(gòu)置空間’來安放噪震吸收材料，而不是直擊車體基本結(jié)構(gòu)的問題。而他們對(duì)此的解釋就是吸收材料比較輕。”
緩沖墊已經(jīng)成為了將發(fā)動(dòng)機(jī)噪音屏蔽在客廂外的一種戰(zhàn)略性“城防工事”。緩沖墊像“防火墻”一樣覆蓋在隔板兩邊。最初，緩沖墊是充當(dāng)屏障和解耦裝置的，而如今，它的作用無疑是充當(dāng)吸收材料。而作為一種“耗散性”材料，顯然，緩沖墊會(huì)占據(jù)更多剖面空間。
如今，為了追求更高的燃料經(jīng)濟(jì)性，越來越多的OEM開始將目光放在氣缸鈍化等提升能源效率的技術(shù)上，而由于發(fā)動(dòng)機(jī)在開啟/關(guān)閉部分氣缸時(shí)（比如 6 缸切換至 4 缸或 3 缸）會(huì)產(chǎn)生不均勻燃燒，造成發(fā)動(dòng)機(jī)低頻震爆（具體水平取決于傳播路徑有所不同），從而帶來噪聲。為了應(yīng)對(duì)這一獨(dú)特需求，相關(guān) NVH 創(chuàng)新技術(shù)更是層出不窮。
氣缸間歇式發(fā)動(dòng)機(jī)會(huì)帶來一些不同以往的NVH問題，緩解這些問題的有效方案有很多，如：控制扭矩轉(zhuǎn)換離合器打滑時(shí)，采用發(fā)動(dòng)機(jī)主動(dòng)制動(dòng)控制系統(tǒng)（AEB）和變速箱支撐膠墊（效果好但成本高），以及使用車內(nèi)音響系統(tǒng)主動(dòng)降噪等等。[更多詳情請(qǐng)參閱SAE技術(shù)論文 2014-01-1675，由Tula Technologies發(fā)布]合成材料會(huì)在一些扭矩反作用應(yīng)用上產(chǎn)生吸收震動(dòng)的效果。基于此，Cooper-Standard正在一款歐洲車型上使用連續(xù)纖維的熱塑性塑料發(fā)動(dòng)機(jī)支架。
整車建模
NVH方面的建模已經(jīng)相當(dāng)成熟了。其核心就是統(tǒng)計(jì)能量分析（SEA）工具，包括Cambridge Collaborative Inc.研發(fā)的SEAM 3D，以研究潛水艇的結(jié)構(gòu)噪音。自此，汽車業(yè)就將其作為了一種有效的CAE設(shè)計(jì)工具，用來研發(fā)NVH聲音工具，為輕巧型車型設(shè)計(jì)服務(wù)。通過使用SEA，工程師能評(píng)估在中頻和高頻時(shí)復(fù)雜結(jié)構(gòu)的動(dòng)態(tài)反應(yīng)，并彌補(bǔ)輕量化設(shè)計(jì)帶來的NVH方面的不足。
SEA“能讓聲學(xué)工程師采用‘控制變量法’做研發(fā)，”Pranab Saha說，“比如說，某個(gè)組件的質(zhì)量減輕后，噪音水平會(huì)怎么變？”
通用汽車最近開始使用一種內(nèi)部開發(fā)的建模工具，叫做DISPET。DISPET能讓工程師把NVH工具包在不同車型中的作用發(fā)揮到最大。在開始時(shí)錄入車身設(shè)計(jì)和動(dòng)力系統(tǒng)噪音后，就能具體指定所需的NVH材料。“就給定的厚度和表面密度，用戶只要輸入測(cè)得的聲音數(shù)據(jù)即可，”一位熟悉DISPET的工程師告訴我們，“系統(tǒng)會(huì)告訴你是否達(dá)到預(yù)期的降噪目標(biāo)。而如果你自己不知道目標(biāo)數(shù)值是多少，DISPET會(huì)告訴你，在某個(gè)頻率下，數(shù)值是否高了或低了一分貝。”
整車NVH模擬技術(shù)在業(yè)界有有很強(qiáng)的競(jìng)爭(zhēng)優(yōu)勢(shì)，因此，各家OEM對(duì)其內(nèi)部程序的具體運(yùn)作守口如瓶。大約五年前，Altair Engineering在這一技術(shù)的商業(yè)化方面處于領(lǐng)先。Altair的NVH模擬器樣子很像電腦游戲的手柄，你的面前有一塊巨大的液晶屏，駕駛員就在屏幕里的“路上”。
“有了整車模擬器后，我們又建了一個(gè)相關(guān)的模型，可以利用測(cè)試數(shù)據(jù)模擬出在某一噪音和震動(dòng)環(huán)境下駕駛汽車的場(chǎng)景。”Altair降噪減震的項(xiàng)目總監(jiān)Jiamin Guan解釋道，“這一模擬需要汽車在不同環(huán)境條件下駕駛時(shí)的數(shù)據(jù)，同時(shí)，也會(huì)讓你有身臨其境的噪音感受。”
Altair與著名的專業(yè)儀表公司Brüel &Kjaer合作，共同開發(fā)出了這套能盡享“實(shí)車”體驗(yàn)的模型。模型是在某一汽車項(xiàng)目著手之初就建好的，也就是在設(shè)定標(biāo)桿和具體規(guī)格時(shí)。Altair的第一步就是想象有一個(gè)虛擬的目標(biāo)客戶，然后怎樣找到一款符合其要求的車。之后建模團(tuán)隊(duì)給出各種可行性較高的方案，進(jìn)行包裝并增加功能需求，接著讓客戶來聆聽與感受這些測(cè)量出的數(shù)據(jù)。
整車模型“可以讓社會(huì)中不同層次的客戶群體來體驗(yàn)各種我們想要確定采用的噪音和震動(dòng)水平，并讓我們知道人們是否認(rèn)可這些數(shù)值。”Guan談到，“回放這些噪音和震動(dòng)水平后，我們可以在某些地方進(jìn)行精修。我們可以了解人們喜歡的是什么，不能接受的什么，以及更看重怎樣的‘音效’。一旦我們有了具體的目標(biāo)數(shù)值，無論是對(duì)于我們還是客戶而言，接下來要考慮的就是如何實(shí)現(xiàn)它們了。”
Guan稱，整車建模工具讓工程師能夠在汽車重量和成本一定的前提下，自由地進(jìn)行改進(jìn)，并評(píng)估這些概念性的想法。“如果沒有整車建模，很多東西我們就無法確定。比如說，相比鋼結(jié)構(gòu)的車身，鋁材質(zhì)對(duì)于震動(dòng)的影響大小有多少。有些構(gòu)思可以通過整車建模來評(píng)估，無論最終是否能夠達(dá)標(biāo)。”
大多數(shù)的NVH討論會(huì)似乎都繞不開汽車電動(dòng)化這個(gè)話題。對(duì)于聲學(xué)以及N&V方面的專家而言，這一趨勢(shì)會(huì)讓他們的工作變簡(jiǎn)單還是變得更難呢？“我們接到電話，讓我們從聲學(xué)和密封性兩方面給電動(dòng)汽車的隔音系統(tǒng)拿主意。”Pranab Saha說，“盡管我們還沒有感受到很大的變化，但顯然供應(yīng)面轉(zhuǎn)向電動(dòng)汽車應(yīng)該是大勢(shì)所趨。”Saha和其他專家都提到，盡管電動(dòng)汽車的整體噪音減小了，但此前被內(nèi)燃機(jī)掩蓋的其他噪音則現(xiàn)了原形。
Saha表示，“NVH專家仍在努力調(diào)試新的隔音系統(tǒng)，以應(yīng)對(duì)今后電動(dòng)汽車頻段上的新挑戰(zhàn)。”
The vehicle chief engineer did not like what he was hearing on this recent evaluation ride.
He was reviewing a new transmission scheduled for production in his company’s iconic sporty car. But the marriage of transmission and platform was generating unacceptably high cabin-noise levels. The CE wasn’t pleased. His design and manufacturing engineers explained that the new gearbox featured a thin-wall aluminum case for reduced mass. However, the lightweight case was the noise transmitter.
The tooling investment had been made and the program clock was ticking. So a phone call went out to Pranab Saha.
“They called me in to help them devise a solution,” said Saha, an acoustics expert and board-certified noise control engineer with consultants Kolano & Saha in Waterford, MI. He said the client’s original design blanketed the lightweight transmission case with a foil-backed insulation material. Problem was, the blanket included multiple cut-outs so that linkages and wiring could pass through. The cut-outs were built-in noise paths.
Saha’s suggestion: Rather than place the insulation material on the transmission case, put it on the underside of the transmission tunnel. The engineers would revisit their CAD drawings and revised the parts. Their next step is to launch noise study to prove the new solution’s effectiveness.
“That’s one of many examples of us getting called in to solve a problem—where is the best place to install NVH countermeasures?” he noted.
The science of analyzing, attenuating and eliminating Noise, Vibration and Harshness has become an integral aspect of vehicle development. NVH engineering teams now push for “one dB [decibel] per day” reductions in cabin noise levels with the same verve that is devoted to vehicle mass reduction and greater fuel efficiency.
“The N&V [noise and vibration] discipline is unique because it’s driven by market competition, rather than by government legislation,” Saha explained. “The OEMs now brag about the superior interior sound quality and low noise levels of one model versus another. And this will certainly grow more important as technologies such as cylinder deactivation, hybrids and electric vehicles enter the market.”
Quieter and smoother are requisites for the new human-machine interfaces (HMI) being developed for automated vehicles, said Joe Emmi, vice president of global product strategy and head of the Anti-Vibration Systems group at Cooper-Standard. “Reduced cabin noise is particularly important for voice-recognition systems,” he noted.
OEMs and Tier 1s have invested billions in new NVH software, facilities, materials R&D and in the expertise of Saha and other acoustics specialists in the field. Makers of the absorptive materials that are vital to automotive NVH abatement also are riding a growth curve. The global market for their products is projected to reach $13.52 billion by 2021, at a compounded annual growth rate of 6% from 2016 to 2021, according to a 2017 study by Grand View Research.
Astute suppliers are branding their technologies to suit. The growing list includes Material Sciences Corp.’s “Quiet Steel” used in dash panels; Japan-based Technol Polymer Co. Ltd’s “Hushlloy” anti-squeak thermoplastics, and Sika Automotive’s “Sika Damp,” a co-extruded elastomer aimed at dampening body-panel resonance.
The industry’s commitment to NVH engineering has driven the market for dedicated software programs familiar to engineers: SCS’s V-Path for transfer path analysis; HEAD Acoustics’ Artemis; Genesis’ LEA; Altair Engineering’s HyperWorks suite, as well as NVH toolsets built into Dassault Systemes’ CATIA V6/3DS, Siemens PLM and many others.
SAE International has long served as a professional forum for NVH engineers, with its biennial Noise and Vibration Conference and Exhibition (held this month in Grand Rapids, MI) the premier technical event on the subject.
Playing the ‘what-if?’ game
N&V engineers live in a realm of Sources, Paths (structure-borne and airborne) and Receivers (the noise and vibration targets) where up-front problem identification and solving are critical to success. They focus on quantifying the relationship between objective parameters, such as precise sound and frequency measurements obtained through data-acquisition methods, with a degree of informed subjectivity.
End-customer input is part of the analysis process; to many of them enhancing sound quality is as important as reducing annoying noises and overall volume. Psycho-acoustics specialists agree. Loudness, sharpness and the articulation index (a measure of the intelligibility of hearing speech within a given noise environment) are all subjective parameters.
Experts interviewed for this article agree that lightweight aluminum body structures, in modal analysis, present different and often more challenging N&V characteristics than do steel structures. Keeping vibration in check requires greater stiffness in the body panels and additional damping materials such as LASD (liquid applied sprayable dampening) underbody mastics and cavity-filling foams.
In some applications, active noise control systems are employed (see Honda sidebar). Such solutions are sometimes dubbed “band aids” because they don’t address root causes that typically originate in a fundamental structure—an excessively resonant cylinder block, for example. And they add mass.
Observed Richard Yen, Senior VP Automotive at Altair Engineering: “A lot of companies do a good job in NVH but basically they’re applying a lot of testing at the end of the vehicle development cycle. They spend a lot of money trying to fix the problems.”
When working with aluminum, engineers often add more material to achieve the same amount of NVH reduction of a heavier steel structure. As a result, NVH specialists “see evidence of trying to ‘buy more space’ within the vehicle to make room for absorptive materials, instead of addressing the fundamental structure issues,” said Saha. “They rationalize that absorption materials don’t weigh as much.”
Dash mats have become a strategic bulwark in the battle to keep powertrain noise out of the passenger cabin. The mats cover both sides of the bulkhead formerly known as the firewall. They used to serve as a barrier and decoupler. Today, dash mates essentially play an absorptive role. Known as ‘dissipative’ materials, they require more cross-sectional space.
The growing number of OEMs who have embraced engine cylinder deactivation as a fuel-efficiency play is sparking innovations related to NVH created by the uneven firing when a 60° V6 switches to V4 and V3 operating mode, for example. Signature vibrations and acoustic patterns are created by these events, with powertrain excitation entering the cabin as low-frequency “boom,” depending on the leak paths.
Managing torque-converter clutch slip, adoption of active engine and transmission mounts (typically effective but costly) and active noise control using the vehicle’s audio system can be effective solutions for mitigating the unique NVH challenges of cylinder-deactivation engines. [SAE Technical Paper 2014-01-1675, published by Tula Technologies, offers more detail on this subject.] Composites offer vibration-absorbing benefits in some torque-reaction applications. For this reason Cooper-Standard is launching a new continuous-fiber thermoplastic engine mount on a European vehicle.
Full Vehicle Modeling
Modeling in the NVH arena is increasingly sophisticated. Core among them are SEA (Statistical Energy Analysis) packages including SEAM 3D, developed by Cambridge Collaborative Inc. to study structure-borne noise in submarines. It has since been adopted by the auto industry as an effective CAE design tool to develop NVH sound packages for use in lightweight vehicle design. Using SEA, engineers can evaluate the dynamic response of complex structures at mid and high frequencies and recover the NVH deficiency created by the lightweighting actions.
SEA “enables acoustics engineers to play the ‘what-if’ game,” said Pranab Saha. “For example, if mass is reduced in a subassembly, what then will be the noise level?”
General Motors recently began using a modeling tool developed in-house called DISPET that lets engineers optimize NVH packages across vehicle families. With primary inputs being vehicle body design and powertrain noise, they can specify the NVH materials needed. “Users only input the measured acoustic data for a given thickness and surface density,” says an engineer familiar with DISPET. “The system will tell you if it meets the target or not. And if you don’t know the target, DISPET will tell you if you’re 1 dB above or 1dB below (or not), at every frequency.”
Full-vehicle NVH simulation is viewed as a competitive advantage whose internal processes the OEMs guard closely. About five years ago, Altair Engineering took the lead on commercialization. Altair’s NVH Simulator looks like the console of a cool computer video game, with a big flatscreen in front of you puts the driver “on the road.”
“With the Full-Vehicle Simulator, we build a simulation model that uses testing data to drive a model of the vibration and acoustic environment in the vehicle,” explained Jiamin Guan, Altair’s Director of Vibration and Acoustic Solutions. “It takes data from vehicle operation under various conditions and allows you to listen to those as you would hear them in a real vehicle.”
Altair partners with noted instrumentation specialists Brüel & Kjaer to create the “real vehicle” experience. The model is built right at the beginning of a vehicle program, during benchmarking and setting specifications. Altair starts with an imagined target customer and how the vehicle fits into their usage. The model team then builds a competitive set, adds packaging and functional requirements, then brings in customers to listen to and experience the measured data.
The full-vehicle model “allows a broad spectrum of people to experience the noise and vibration levels we’re trying to target—and see if they agree with those targets,” Guan noted. “Based on the playback of the noise and vibration we hone in on specific areas. We see what people really prefer and object to and what “sound quality” means to them. Once we have the targets, this helps us and the client consider how we will achieve them.”
The tool, Guan claims, gives engineers the freedom to make changes and evaluate conceptual options under weight and cost constraints. “Without a full-vehicle model we wouldn’t be able to determine how aluminum, for example, factors into the vibration requirement versus a steel vehicle. These are constructs you can evaluate in the full-vehicle model, whether you can meet the targets or not.”
The subject of Vehicle Electrification seems to enter most conversations about NVH. Is it making acoustics and N&V experts’ jobs easier or more difficult? “We’re getting calls to help decide on sound-package materials—acoustics and seals—for new EV programs,” said Pranab Saha. “The supply base is moving on this trend although we haven’t seen dramatic changes yet.” He and other experts noted that although EVs’ overall sound level is low, other noises previously masked by the combustion engine are now more audible.
“NVH engineers are still working out the sound packages to address the new frequency ranges of future electrified vehicles,” he explained.
汽車聲學(xué)工程師最熟悉的一幕：專家正在測(cè)試車內(nèi)安裝Aachen HEAD的兩路立體聲測(cè)試系統(tǒng)HMS IV。(Wade Bray / HEAD Acoustics Inc.)
為了讓 2018 款?yuàn)W德賽具備最一流的車艙傳聲清晰指數(shù)，本田投入了大量 NVH 技術(shù)資源。 
一輛典型乘用車NVH系統(tǒng)的平鋪分解圖，顯然這種設(shè)計(jì)會(huì)增加重量。（工程師Kolano 和 Saha提供） 
Pranab Saha，博士，工程師，圖為其站在公司的其中一個(gè)消音測(cè)試艙內(nèi)。（照片來源：Lindsay Brooke）
典型的兩層式消聲緩沖板的工作原理圖
在行業(yè)開始關(guān)注控制 NVH 性能的最初 20 年中，車內(nèi)噪聲水平的下降趨勢(shì)。（來源：Car and Driver）
Altair Engineering 的整車NVH模擬器模擬時(shí)的車內(nèi)環(huán)境。