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Active sound design is an acoustic technology concept used in automotive vehicles to alter or enhance the sound inside and outside of the vehicle. Active sound design (ASD) often uses active noise control and acoustic enhancement techniques to achieve a synthesized vehicle sound.

The typical implementations of ASD vary, from amplifying or reducing an existing sound to creating an entirely new sound. Each vehicle manufacturer may use different software or hardware techniques in ASD, as there is no one unified model. ASD exists under multiple names, like Acura’s Active Sound Control, Kia’s Active Sound System, Volkswagen’s Soundaktor, and QNX’s Acoustic Management System.

The first instance of in-vehicle active noise cancelling (ANC) was developed by Lotus and featured in the 1992 Nissan Bluebird. In 2009, Lotus partnered with Harman International for an improved ANC system that eliminated noise from the road, tires, and vehicle chassis.^[1] With recent demand for economical and cleaner combustion engine vehicles, engine systems have become more efficient but less audibly appealing to consumers. Electric and fuel cell vehicles operate with high-pitched tones, lacking the recognizable sound of a typical combustion engine.^[2] With ASD, both combustion and electrical vehicle manufacturers aim to improve the reception of these vehicles by increasing the quality of interior and exterior vehicle sound.

Components

Active noise cancelling (ANC) is a software process that uses existing in-vehicle infotainment hardware to eliminate undesirable noise within the interior of a vehicle. This elimination technique is known as harmonic order reduction, where unwanted audio signals are identified by sensors and filtered out of the overall interior vehicle sound.^[3] Manufacturers may use ANC within a vehicle to improve the effects of ASD.^[4]

Engine sound enhancement (ESE) is a technology that allows manufacturers to enhance engine sounds with synthetic noise composed from live engine data, including components such as engine revolutions per minute (RPM) and engine torque. This synthetically composed sound is relayed through interior or exterior vehicle speakers. In ASD, manufacturers may use ESE to enhance perceived engine power without the mechanical alterations that other techniques may require.^[5]^[6]

Motivations for ASD

In the face of environmental restrictions and a demand for fuel economy in the automotive industry, smaller engine subsystems have made interior vehicle noise less pleasant in combustion engine vehicles. Electric and hybrid vehicles lack a distinct engine sound altogether, instead featuring a quieter high frequency noise that causes annoyance for vehicle passengers and poses a threat to pedestrians who may not recognize an oncoming vehicle.^[7] These developments have sparked a consumer demand for a more desirable interior sound, as well as a brand identity in both the interior and exterior of the vehicle that is recognizable and mitigates safety risks.^[8]

Traditional iterations of sound control in vehicles included tedious mechanical alterations such as balance shafts and sound-deadening material that increased manufacturing time and cost. With the renewal of sound design in the form of ASD, manufacturing costs and complications are reduced. Instead of integrating the technology into the engine structure, the sound can be fixed at a later stage of development and optimized to the vehicle.^[9]^[2]

Variations

Active sound design (ASD) takes inputs from engine and vehicle speed, pedal input, exhaust noise, and vehicle vibrations to change the interior and exterior noise of the vehicle. These input variables are filtered to produce desired outputs. Variations of ASD select one or multiple of these variables to implement a new sound. These variations include:

Passive sound generation : signals taken directly from the engine output and relayed in the interior of the vehicle.
Passive and active sound generation: amplifying the exhaust input and creating a new output to enhance the vehicle's exterior noise.
Active mounts : taking inputs from the exterior vehicle and feeding vibration outputs to the vehicle interior.
Synthetic sound : generating a new sound through the interior stereo audio.^[2]

Application and Theory

In a typical combustion engine, cylinders are responsible for burning gasoline and producing energy to power the vehicle. These cylinders fire periodically and can be reduced to a series of sinusoidal waves (by conventions of the Fourier transform). These sine waves are dictated by the rotations per minute (RPM) of the engine crankshaft and the firing order, or arrangement, of the cylinders. To enrich engine sound in the passenger cabin, the harmonic orders of engine sound missing from the interior sound can be amplified through Digital Signal Processing (DSP) techniques.^[2]

To capture the missing orders, the engine load condition is identified by acceleration sensors on the engine of older vehicles, or by way of the Controller Area Network bus (CAN-bus) in modern cars^[9]. Using dynamic band-pass filters (a device that relays specified frequencies), the missing orders are passed. To minimize artefacts (disruptive clicks) during the transfer, the signal is passed through cascading high- and low-pass filters. With an adaptation from the engine’s RPM signal (captured by an inductive voltage transformer), the orders are amplified through the vehicle firewall (body separating the engine from the interior) and interior sound system.^[10]

Subharmonics and Sound Signatures

In electric and fuel cell vehicles, virtual (synthetic) sounds are often used to accommodate for the absence of a combustion engine sound. To create the optimal sound design in an electric vehicle (EV), manufacturers must acknowledge the psychoacoustic theories behind sound preference. In a study of diesel engine sound quality, experimental analysis compared a subjective rating of sound quality components with J.D. Power’s APEAL study.^[11] ^[12]

Based on studies of user preference in vehicle interiors, manufacturers aim to reduce loudness increment and high-frequency sound for a more pleasant driving experience. In modern EVs, the stock vehicle noise is masked with an RPM-dependent low-pass-filtered sound. This low-pass-filtered sound is a lower-frequency synthetic sound that is based on the EV’s actual engine parameters, like speed and load.

Alt and Jochum’s simple-integer ratio technique of harmonic order is applied to this virtual noise. Subharmonics (lower-frequency copies) are then isolated from the original high-frequency components of the EV.^[13] In an evaluation of several generated sound stimuli, individuals subjectively identified that these subharmonics were preferable for the interior sound of an EV.^[14]

Combustion engine vehicles respond dynamically to different driving conditions. For manufacturers to synthesize a brand sound in an EV, they must consider a sound signature that encompasses a dynamic driving sound. A base sound signature is defined by a schematic of sub-signatures and micro-signatures that can be expanded to increase the dynamic quality of the sound. These sub-signatures can be assigned to parameters (load, speed) or maneuvers that relay particular sound samples. By synthesizing micro-signatures in EV drivetrains, the resulting sound is more vivid and emotional than the base frequencies of the EV.^[15]

Challenges

Consumer Response

For the average consumer, the advent of ASD goes largely unnoticed. With recent BMW models, however, consumers feel cheated by the synthetic engine sound. Numerous instructional videos featured online give a step-by-step on disabling the ASD within BMW’s vehicles, as well as articles that addressed the false-sounding synthetic noise.^[16]^[17]

Brand Identity for electric and fuel cell vehicles

Typical combustion engine vehicles provide sound feedback during operation that represents the brand identity of the car. Because of the nature of the single gear system and arrangement of power converters in electric and fuel cell vehicles, the frequency of sound changes minimally over a period of acceleration and is not well matched to the actual state of the vehicle speed and load. Additionally, the lack of engine noise leaves a spectral gap (empty space) between wind and road noise and amplifies individual vehicle components, reducing the sound quality inside the cabin.^[2]

To create a brand identity, manufacturers must choose between reproducing a typical combustion engine sound and creating an entirely new sound concept.^[14]

Reproduction of the combustion engine process

Current implementations of active sound design in combustion engine vehicles may not accurately reproduce the micro structure variations (variations between cylinder firings) of the combustion process. As the signal waves originate from multiple periodically firing cylinders, identifying and replicating the harmonic engine orders is an inefficient process. Additionally, this approach assumes uniformity in the combustion engine. The force provided from the cylinders is periodic and may vary from one cycle to another, making it impossible for the natural component of engine noise to be replicated.^[2]

Example Applications

Several automotive companies implement their own branded versions of ASD technology.^[18]

In vehicle models such as the BMW M5, an engine management system enhances the sounds provided by speed and engine power by filtering through the audio data it receives. Drivers can select a driving setting that will modify the interior acoustics as well as the actual performance of the vehicle.^[19]

Similarly, the Kia Stinger features five drive modes (eco, comfort, smart, sport, and custom) that adjust the loudness and aggressiveness of the sound inside the vehicle cabin.^[20] Paired with a turbocharged engine, this vehicle is engineered to adapt to user preferences. The turbocharger increases efficiency and forces additional compressed air into the combustion engine, creating a consistent and clean sound output.

Porsche’s ASD implementation combines a Helmholtz resonator and sound symposer to transport engine sounds directly into the vehicle cabin. The Helmholtz universal resonator restricts engine sound through an electronically controlled valve that oscillates with air, much like the sound that is emitted when one blows over the top of a bottle. The sound symposer consists of a line of plastic tubing with a membrane and flap valve that behave much like a human ear. When the Sport button is pressed, the resonator and sound symposer open fully to amplify the engine sound in the vehicle cabin.^[21]

References

^ "Lotus and Harman partner on noise-cancelling, noise-creating tech". Autoblog. Retrieved 2020-11-12.
^ ^a ^b ^c ^d ^e ^f Bodden, Markus; Belschner, Torsten (2014-10-14). "Comprehensive automotive active sound design - Part 1: Electric and combustion vehicles". INTER-NOISE and NOISE-CON Congress and Conference Proceedings. 249 (4): 3214–3219.
^ Elliott, S. J.; Nelson, P. A. (1993-10). "Active noise control". IEEE Signal Processing Magazine. 10 (4): 12–35. doi:10.1109/79.248551. ISSN 1558-0792. {{cite journal}}: Check date values in: |date= (help)
^ https://ip.cadence.com/uploads/1021/TIP_WP_ActiveNoiseControl_FINAL-pdf
^ "Acoustics Management Platform". blackberry.qnx.com. Retrieved 2020-10-23.
^ Weiinau, Kelby (2019-10-03). "Definition of the Sound Enhancement Preferences for a Sport Vehicle". INTER-NOISE and NOISE-CON Congress and Conference Proceedings. 260 (1): 901–912.
^ Moore, Dylan; Currano, Rebecca; Sirkin, David (2020-09-20). "Sound Decisions: How Synthetic Motor Sounds Improve Autonomous Vehicle-Pedestrian Interactions". 12th International Conference on Automotive User Interfaces and Interactive Vehicular Applications. New York, NY, USA: ACM. doi:10.1145/3409120.3410667. ISBN 978-1-4503-8065-2.
^ L. Garay-Vega, A. Hastings, J. K. Pollard, M. Zuschlag, and M. D. Stearns, “Quieter Cars and the Safety of Blind Pedestrians,” National Highway Traffic Safety Administration, Apr-2010. [Online]. Available: https://www.nhtsa.gov/DOT/NHTSA/NVS/Crash%20Avoidance/Technical%20Publications/2010/811304rev.pdf.+%5BAccessed:+09-Nov-2020%5D.
^ ^a ^b Schirmacher, Rolf (2002). "Active Design of Automotive Engine Sound". undefined. Retrieved 2020-10-25.
^ Sontacchi, Alois; Frank, Matthias; Zotter, Franz; Kranzler, Christian; Brandl, Stephan (2016), Fuchs, Anton; Nijman, Eugenius; Priebsch, Hans-Herwig (eds.), "Sound Optimization for Downsized Engines", Automotive NVH Technology, SpringerBriefs in Applied Sciences and Technology, Cham: Springer International Publishing, pp. 13–27, doi:10.1007/978-3-319-24055-8_2, ISBN 978-3-319-24055-8, retrieved 2020-10-23
^ Heinrichs, Ralf; Bodden, Markus (2007-08-28). "Diesel impulsiveness Part I: Customer perspective". INTER-NOISE and NOISE-CON Congress and Conference Proceedings. 2007 (5): 2463–2468.
^ "U.S. Automotive Performance, Execution and Layout (APEAL) Study". J.D. Power. Retrieved 2020-11-10.
^ "Sound Design Under the Aspects of Musical Harmonic Theory (2003-01-1508 Technical Paper) - SAE Mobilus". saemobilus.sae.org. Retrieved 2020-11-10.
^ ^a ^b Gwak, Doo Young; Yoon, Kiseop; Seong, Yeolwan; Lee, Soogab (2014-11-06). "Application of subharmonics for active sound design of electric vehicles". The Journal of the Acoustical Society of America. 136 (6): EL391–EL397. doi:10.1121/1.4898742. ISSN 0001-4966.
^ Bodden, M.; Belschner, T. (2016). "Principles of Active Sound Design for electric vehicles". www.semanticscholar.org. Retrieved 2020-11-10.
^ "Hear the BMW M2 With and Without Active Sound Design". BMW.SG | BMW Singapore Owners Community. 2016-06-17. Retrieved 2020-11-10.
^ Harwell, Drew (2015-01-21). "America's best-selling cars and trucks are built on lies: The rise of fake engine noise". Washington Post. ISSN 0190-8286. Retrieved 2020-11-12.
^ "Vehicle sound design | Tech - Hyundai Worldwide". HYUNDAI MOTORS. Retrieved 2020-11-10.
^ "BMW M5 with Active Sound Design". sgCarMart.com. Retrieved 2020-11-10.
^ "Experiencing Kia by Sound". www.kia.com. Retrieved 2020-11-10.
^ "Where the Music Comes From - Porsche USA". Porsche HOME - Porsche USA. Retrieved 2020-11-12.

@@ Line 1: / Line 1: @@
+{{Userspace draft|source=ArticleWizard|date=October 2020}}'''Active sound design'''  is an [[Acoustics|acoustic]] technology concept used in [[Motor vehicle|automotive vehicles]] to alter or enhance the [[sound]] inside and outside of the vehicle. Active sound design (ASD) often uses [[active noise control]] and [[acoustic enhancement]] techniques to achieve a synthesized vehicle sound.
-'''Active sound design''' (ASD) is an automotive audio application in which the car engine's sound is generated based on various engine parameters like speed and throttle input. This technology is implemented in [[BMW M5]] and [[Renault Clio]].<ref>http://www.autoblog.com/2011/09/23/active-sound-design-enhances-v8-burble-inside-bmw-m5/</ref>
+The typical implementations of ASD vary, from amplifying or reducing an existing sound to creating an entirely new sound. Each vehicle manufacturer may use different [[software]] or [[Electronic hardware|hardware]] techniques in ASD, as there is no one unified model. ASD exists under multiple names, like Acura’s [https://www.autobytel.com/car-ownership/technology/what-is-acura-active-sound-control-125813/ Active Sound Control], Kia’s [https://www.kia.com/worldwide/KiaBuzz/Stories/View.do?SEQ=23 Active Sound System], Volkswagen’s [[Soundaktor]], and QNX’s [https://blackberry.qnx.com/en/products/acoustic/sound-design Acoustic Management System].
-Some people feel that the sounds these systems generate to mimic engine and transmission noises are inauthentic and, as a result, they disable them.<ref>{{cite web |last1=Adams |first1=Eric |title=From Acura to VW, BMW to Porsche, Car Companies Are Getting Sneakier About Engine Sound Enhancement |url=https://www.thedrive.com/tech/22834/from-acura-to-vw-bmw-to-porsche-car-companies-are-getting-sneakier-about-engine-sound-enhancement |website=The Drive |publisher=The Drive Media, Inc. |accessdate=29 July 2019}}</ref> This application was founded by the Korea Ministry of Environment (MOE) as the "Environmental Health Action Program".<ref>{{Cite journal|url=https://asa-scitation-org.ez/doi/abs/10.1121/1.4898742|title=Application of subharmonics for active sound design of electric vehicles|journal=The Journal of the Acoustical Society of America|year=2014|doi=10.1121/1.4898742|access-date=2019-07-28|last1=Gwak|first1=Doo Young|last2=Yoon|first2=Kiseop|last3=Seong|first3=Yeolwan|last4=Lee|first4=Soogab|volume=136|issue=6|pages=EL391–EL397|pmid=25480088}}</ref> Although this application is a relatively new idea, car industries have been making great strides. Various technologies are being employed to enhance vehicle engine sound including things such as active control systems.<ref>{{Cite web|url=http://web.b.ebscohost.com.ez/ehost/detail/detail?vid=0&sid=df134693-ea3b-4de6-8366-5b33d470b309%40sessionmgr102&bdata=JnNpdGU9ZWhvc3QtbGl2ZSZzY29wZT1zaXRl#AN=117552014&db=a9h|title=Development of Personalized Engine Sound System using Active Sound Design Technology|website=SAE International Journal of Passenger Cars|access-date=2019-07-28}}</ref> The purpose of '''active sound design''' is to provide customers with cars that make the sounds they prefer. The main goal for car manufacturers is to appeal to the buyers by allowing them to buy a certain car and giving them the opportunity to make it sound like another.<ref>{{Cite journal|url=https://asa-scitation-org.ez/doi/abs/10.1121/1.4785459|title=New development of two-dimensional sound index for the design of brand sound in the passenger cars|journal=The Journal of the Acoustical Society of America|year=2004|doi=10.1121/1.4785459|access-date=2019-07-28|last1=Lee|first1=Sang‐Kwon|last2=Jo|first2=Byung‐Og|last3=Kim|first3=Byung‐Soo|volume=116|issue=4|page=2623}}</ref>
+The first instance of in-vehicle active noise cancelling (ANC) was developed by [[Lotus Cars|Lotus]] and featured in the 1992 [[Nissan Bluebird]]. In 2009, Lotus partnered with [[Harman International]] for an improved ANC system that eliminated noise from the road, tires, and vehicle [[chassis]].<ref>{{Cite web|title=Lotus and Harman partner on noise-cancelling, noise-creating tech|url=https://www.autoblog.com/2009/04/16/lotus-and-harman-partner-on-noise-cancelling-noise-creating-tec/|access-date=2020-11-12|website=Autoblog|language=en}}</ref> With recent demand for economical and cleaner [[Internal combustion engine|combustion engine]] vehicles, [[engine]] systems have become more efficient but less audibly appealing to consumers. [[Electric vehicle|Electric]] and [[Fuel cell vehicle|fuel cell vehicles]] operate with high-pitched [[Musical tone|tones]], lacking the recognizable sound of a typical combustion engine.<ref name=":0">{{Cite journal|last=Bodden|first=Markus|last2=Belschner|first2=Torsten|date=2014-10-14|title=Comprehensive automotive active sound design - Part 1: Electric and combustion vehicles|url=https://www.ingentaconnect.com/content/ince/incecp/2014/00000249/00000004/art00011|journal=INTER-NOISE and NOISE-CON Congress and Conference Proceedings|volume=249|issue=4|pages=3214–3219}}</ref> With ASD, both combustion and electrical vehicle manufacturers aim to improve the reception of these vehicles by increasing the quality of interior and exterior vehicle sound.
+=== Components ===
+'''Active noise cancelling''' (ANC) is a [[software]] process that uses existing [[In-car entertainment|in-vehicle infotainment]] hardware to eliminate undesirable [[noise]] within the interior of a vehicle. This elimination technique is known as [https://www.ecmweb.com/content/article/20897096/fundamentals-of-harmonics#:~:text=We%20define%20harmonics%20as%20voltages,%2C%20200%20Hz%2C%20etc.) harmonic order] reduction, where unwanted [[Audio signal|audio signals]] are identified by [[Sensor|sensors]] and filtered out of the overall interior vehicle sound.<ref>{{Cite journal|last=Elliott|first=S. J.|last2=Nelson|first2=P. A.|date=1993-10|title=Active noise control|url=https://ieeexplore.ieee.org/document/248551|journal=IEEE Signal Processing Magazine|volume=10|issue=4|pages=12–35|doi=10.1109/79.248551|issn=1558-0792}}</ref> Manufacturers may use ANC within a vehicle to improve the effects of ASD.<ref>https://ip.cadence.com/uploads/1021/TIP_WP_ActiveNoiseControl_FINAL-pdf</ref>
+'''Engine sound enhancement''' (ESE) is a [[technology]] that allows manufacturers to [[Acoustic enhancement|enhance]] engine sounds with synthetic noise composed from live engine [[data]], including components such as engine [[Revolutions per minute|revolutions per minute (RPM]]) and engine [[torque]]. This synthetically composed sound is relayed through interior or exterior vehicle [[Loudspeaker|speakers]]. In ASD, manufacturers may use ESE to enhance perceived [[engine power]] without the mechanical alterations that other techniques may require.<ref>{{Cite web|title=Acoustics Management Platform|url=https://blackberry.qnx.com/en/products/acoustic/sound-design|access-date=2020-10-23|website=blackberry.qnx.com}}</ref><ref>{{Cite journal|last=Weiinau|first=Kelby|date=2019-10-03|title=Definition of the Sound Enhancement Preferences for a Sport Vehicle|url=https://www.ingentaconnect.com/content/ince/incecp/2019/00000260/00000001/art00102|journal=INTER-NOISE and NOISE-CON Congress and Conference Proceedings|volume=260|issue=1|pages=901–912}}</ref>
+=== Motivations for ASD ===
+In the face of [[Environmental protection|environmental restrictions]] and a demand for [[Fuel economy in automobiles|fuel economy]] in the [[automotive industry]], smaller engine [[System|subsystems]] have made interior vehicle noise less pleasant in combustion engine vehicles. Electric and [[Hybrid vehicle|hybrid]] vehicles lack a distinct engine sound altogether, instead featuring a quieter [[high frequency]] noise that causes annoyance for vehicle passengers and poses a threat to pedestrians who may not recognize an oncoming vehicle.<ref>{{Cite journal|last=Moore|first=Dylan|last2=Currano|first2=Rebecca|last3=Sirkin|first3=David|date=2020-09-20|title=Sound Decisions: How Synthetic Motor Sounds Improve Autonomous Vehicle-Pedestrian Interactions|url=http://dx.doi.org/10.1145/3409120.3410667|journal=12th International Conference on Automotive User Interfaces and Interactive Vehicular Applications|location=New York, NY, USA|publisher=ACM|doi=10.1145/3409120.3410667|isbn=978-1-4503-8065-2}}</ref> These developments have sparked a consumer demand for a more desirable interior sound, as well as a [[Brand|brand identity]] in both the interior and exterior of the vehicle that is recognizable and mitigates safety risks.<ref>L. Garay-Vega, A. Hastings, J. K. Pollard, M. Zuschlag, and M. D. Stearns, “Quieter Cars and the Safety of Blind Pedestrians,” ''National Highway Traffic Safety Administration'', Apr-2010. [Online]. Available: https://www.nhtsa.gov/DOT/NHTSA/NVS/Crash%20Avoidance/Technical%20Publications/2010/811304rev.pdf.+%5BAccessed:+09-Nov-2020%5D.</ref>
+Traditional iterations of sound control in vehicles included tedious mechanical alterations such as [[Balance shaft|balance shafts]] and [[Absorption (acoustics)|sound-deadening]] material that increased manufacturing time and cost. With the renewal of sound design in the form of ASD, manufacturing costs and complications are reduced. Instead of integrating the technology into the engine structure, the sound can be fixed at a later stage of development and optimized to the vehicle.<ref name=":1">{{Cite web|last=Schirmacher|first=Rolf|date=2002|title=Active Design of Automotive Engine Sound|url=https://www.semanticscholar.org/paper/Active-Design-of-Automotive-Engine-Sound-Schirmacher/1f2314c3ed8d75a2fb68fc23316eb7117716cea3|access-date=2020-10-25|website=undefined|language=en}}</ref><ref name=":0" />
+=== Variations ===
+Active sound design (ASD) takes [[Input/output|inputs]] from engine and vehicle [[speed]], pedal input, [[Exhaust system|exhaust]] noise, and vehicle [[Vibration|vibrations]] to change the interior and exterior noise of the vehicle. These input variables are [[Filter (signal processing)|filtered]] to produce desired [[Input/output|outputs]]. Variations of ASD select one or multiple of these variables to implement a new sound. These variations include:
+* '''Passive sound generation''' : [[Signal|signals]] taken directly from the engine output and relayed in the interior of the vehicle.
+* '''Passive and active sound generation''': amplifying the exhaust input and creating a new output to enhance the vehicle's exterior noise.
+* '''Active mounts''' : taking inputs from the exterior vehicle and feeding vibration outputs to the vehicle interior.
+* '''Synthetic sound''' : generating a new sound through the interior [[Vehicle audio|stereo audio]].<ref name=":0" />
+=== Application and Theory ===
+In a typical combustion engine, [[Cylinder (engine)|cylinders]] are responsible for burning gasoline and producing [[energy]] to power the vehicle. These cylinders fire [[Periodic function|periodically]] and can be reduced to a series of [[Sine wave|sinusoidal waves]] (by conventions of the [[Fourier transform]]). These sine waves are dictated by the rotations per minute (RPM) of the engine [[crankshaft]] and the [[firing order]], or arrangement, of the cylinders. To enrich engine sound in the passenger cabin, the [[Harmonics (electrical power)|harmonic orders]] of engine sound missing from the interior sound can be amplified through [[Digital signal processing|Digital Signal Processing]] (DSP) techniques.<ref name=":0" />
+To capture the missing orders, the [[Mechanical load|engine load]] condition is identified by [[Accelerometer|acceleration sensors]] on the engine of older vehicles, or by way of the [[CAN bus|Controller Area Network bus]] (CAN-bus) in modern cars<ref name=":1" />. Using dynamic [[Band-pass filter|band-pass filters]] (a device that relays specified [[Frequency|frequencies]]), the missing orders are passed. To minimize [[Noise|artefacts]] (disruptive clicks) during the transfer, the signal is passed through cascading high- and low-pass filters. With an adaptation from the engine’s RPM signal (captured by an [https://ieeexplore.ieee.org/document/8521570 inductive voltage transformer]), the orders are amplified through the vehicle [[Firewall (engine)|firewall]] (body separating the engine from the interior) and interior sound system.<ref>{{Citation|last=Sontacchi|first=Alois|title=Sound Optimization for Downsized Engines|date=2016|url=https://doi.org/10.1007/978-3-319-24055-8_2|work=Automotive NVH Technology|pages=13–27|editor-last=Fuchs|editor-first=Anton|series=SpringerBriefs in Applied Sciences and Technology|place=Cham|publisher=Springer International Publishing|language=en|doi=10.1007/978-3-319-24055-8_2|isbn=978-3-319-24055-8|access-date=2020-10-23|last2=Frank|first2=Matthias|last3=Zotter|first3=Franz|last4=Kranzler|first4=Christian|last5=Brandl|first5=Stephan|editor2-last=Nijman|editor2-first=Eugenius|editor3-last=Priebsch|editor3-first=Hans-Herwig}}</ref>
+==== Subharmonics and Sound Signatures ====
+In electric and fuel cell vehicles, virtual (synthetic) sounds are often used to accommodate for the absence of a combustion engine sound. To create the optimal sound design in an electric vehicle (EV), manufacturers must acknowledge the [[Psychoacoustics|psychoacoustic]] theories behind sound preference. In a study of [[diesel engine]] sound quality, experimental analysis compared a subjective rating of sound quality components with [[J.D. Power]]’s APEAL study.<ref>{{Cite journal|last=Heinrichs|first=Ralf|last2=Bodden|first2=Markus|date=2007-08-28|title=Diesel impulsiveness Part I: Customer perspective|url=https://www.ingentaconnect.com/contentone/ince/incecp/2007/00002007/00000005/art00081|journal=INTER-NOISE and NOISE-CON Congress and Conference Proceedings|volume=2007|issue=5|pages=2463–2468}}</ref> <ref>{{Cite web|title=U.S. Automotive Performance, Execution and Layout (APEAL) Study|url=https://www.jdpower.com/business/automotive/us-automotive-performance-execution-and-layout-apeal-study|access-date=2020-11-10|website=J.D. Power|language=en}}</ref>
+Based on studies of user preference in vehicle interiors, manufacturers aim to reduce [[loudness]] increment and high-frequency sound for a more pleasant driving experience. In modern EVs, the stock vehicle noise is masked with an RPM-dependent [[Low-pass filter|low-pass-filter]]<nowiki/>ed sound. This low-pass-filtered sound is a lower-frequency synthetic sound that is based on the EV’s actual engine parameters, like speed and load.
+Alt and Jochum’s simple-[[integer]] ratio technique of [[harmonic]] order is applied to this virtual noise. Subharmonics (lower-frequency copies) are then isolated from the original [[High frequency|high-frequency]] components of the EV.<ref>{{Cite web|title=Sound Design Under the Aspects of Musical Harmonic Theory (2003-01-1508 Technical Paper) - SAE Mobilus|url=https://saemobilus.sae.org/content/2003-01-1508/|access-date=2020-11-10|website=saemobilus.sae.org|language=en}}</ref> In an evaluation of several generated sound stimuli, individuals subjectively identified that these subharmonics were preferable for the interior sound of an EV.<ref name=":2">{{Cite journal|last=Gwak|first=Doo Young|last2=Yoon|first2=Kiseop|last3=Seong|first3=Yeolwan|last4=Lee|first4=Soogab|date=2014-11-06|title=Application of subharmonics for active sound design of electric vehicles|url=https://asa.scitation.org/doi/full/10.1121/1.4898742|journal=The Journal of the Acoustical Society of America|volume=136|issue=6|pages=EL391–EL397|doi=10.1121/1.4898742|issn=0001-4966}}</ref>
+Combustion engine vehicles respond dynamically to different driving conditions. For manufacturers to synthesize a brand sound in an EV, they must consider a sound signature that encompasses a dynamic driving sound. A base sound signature is defined by a schematic of sub-signatures and micro-signatures that can be expanded to increase the dynamic quality of the sound. These sub-signatures can be assigned to parameters (load, speed) or maneuvers that relay particular [[Sampling (music)|sound samples]]. By synthesizing micro-signatures in EV [[Drivetrain|drivetrains]], the resulting sound is more vivid and emotional than the base frequencies of the EV.<ref>{{Cite web|last=Bodden|first=M.|last2=Belschner|first2=T.|date=2016|title=Principles of Active Sound Design for electric vehicles|url=https://www.semanticscholar.org/paper/Principles-of-Active-Sound-Design-for-electric-Bodden-Belschner/bc199cacd8199885bdb748e2384a6729f2e62ceb|access-date=2020-11-10|website=www.semanticscholar.org|language=en}}</ref>
+=== Challenges ===
+==== Consumer Response ====
+For the average consumer, the advent of ASD goes largely unnoticed. With recent BMW models, however, consumers feel cheated by the synthetic engine sound. Numerous instructional videos featured online give a step-by-step on disabling the ASD within BMW’s vehicles, as well as articles that addressed the false-sounding synthetic noise.<ref>{{Cite web|date=2016-06-17|title=Hear the BMW M2 With and Without Active Sound Design|url=https://www.bmw-sg.com/bmw-models/hear-bmw-m2-without-active-sound-design/2016/06/17/|access-date=2020-11-10|website=BMW.SG {{!}} BMW Singapore Owners Community|language=en-US}}</ref><ref>{{Cite news|last=Harwell|first=Drew|date=2015-01-21|title=America’s best-selling cars and trucks are built on lies: The rise of fake engine noise|language=en-US|work=Washington Post|url=https://www.washingtonpost.com/business/economy/americas-best-selling-cars-and-trucks-are-built-on-lies-the-rise-of-fake-engine-noise/2015/01/21/6db09a10-a0ba-11e4-b146-577832eafcb4_story.html|access-date=2020-11-12|issn=0190-8286}}</ref>
+==== Brand Identity for electric and fuel cell vehicles ====
+Typical combustion engine vehicles provide sound feedback during operation that represents the brand identity of the car. Because of the nature of the [[Electric motor|single gear]] system and arrangement of [[Electric power conversion|power converters]] in electric and fuel cell vehicles, the frequency of sound changes minimally over a period of acceleration and is not well matched to the actual state of the vehicle speed and load. Additionally, the lack of engine noise leaves a spectral gap (empty space) between wind and road noise and amplifies individual vehicle components, reducing the sound quality inside the cabin.<ref name=":0" />
+To create a brand identity, manufacturers must choose between reproducing a typical combustion engine sound and creating an entirely new sound concept.<ref name=":2" />
+==== Reproduction of the combustion engine process ====
+Current implementations of active sound design in combustion engine vehicles may not accurately reproduce the micro structure variations (variations between [[Cylinder (engine)|cylinder]] firings) of the combustion process. As the [[Signal processing|signal waves]] originate from multiple [[Periodic function|periodically]] firing cylinders, identifying and replicating the harmonic engine orders is an inefficient process. Additionally, this approach assumes uniformity in the combustion engine. The [[force]] provided from the cylinders is periodic and may vary from one cycle to another, making it impossible for the natural component of engine noise to be replicated.<ref name=":0" />
+=== Example Applications ===
+Several automotive companies implement their own branded versions of ASD technology.<ref>{{Cite web|title=Vehicle sound design {{!}} Tech - Hyundai Worldwide|url=https://www.hyundai.com/worldwide/en/brand/designers-of-sound|access-date=2020-11-10|website=HYUNDAI MOTORS|language=en}}</ref>
+* In vehicle models such as the [[BMW M5]], an [[Engine control unit|engine management system]] enhances the sounds provided by speed and engine power by filtering through the audio data it receives. Drivers can select a driving setting that will modify the interior acoustics as well as the actual performance of the vehicle.<ref>{{Cite web|title=BMW M5 with Active Sound Design|url=https://www.sgcarmart.com/news/article.php?AID=4822|access-date=2020-11-10|website=sgCarMart.com|language=en-us}}</ref>
+* Similarly, the [[Kia Stinger]] features five drive modes (eco, comfort, smart, sport, and custom) that adjust the loudness and aggressiveness of the sound inside the vehicle cabin.<ref>{{Cite web|title=Experiencing Kia by Sound|url=https://www.kia.com:443/Default.do|access-date=2020-11-10|website=www.kia.com|language=en}}</ref> Paired with a [[Turbocharger|turbocharged]] engine, this vehicle is engineered to adapt to user preferences. The [[turbocharger]] increases efficiency and forces additional [[compressed air]] into the combustion engine, creating a consistent and clean sound output.
+* [[Porsche]]’s ASD implementation combines a [[Helmholtz resonance|Helmholtz resonator]] and sound symposer to transport engine sounds directly into the vehicle cabin. The Helmholtz universal resonator restricts engine sound through an electronically controlled valve that [[Oscillation|oscillates]] with air, much like the sound that is emitted when one blows over the top of a bottle. The sound symposer consists of a line of plastic tubing with a [[membrane]] and flap [[valve]] that behave much like a human ear. When the Sport button is pressed, the resonator and sound symposer open fully to amplify the engine sound in the vehicle cabin.<ref>{{Cite web|title=Where the Music Comes From - Porsche USA|url=https://www.porsche.com/usa/aboutporsche/christophorusmagazine/archive/369/articleoverview/article06/|access-date=2020-11-12|website=Porsche HOME - Porsche USA|language=en-US}}</ref>
+==References==<!--- See http://en.wikipedia.org/wiki/Wikipedia:Footnotes on how to create references using <ref></ref> tags, these references will then appear here automatically-->
+<references group="" responsive="1"></references>
+== External links ==
+* https://ieeexplore.ieee.org/document/8521570
+* https://www.ecmweb.com/content/article/20897096/fundamentals-of-harmonics#:~:text=We%20define%20harmonics%20as%20voltages,%2C%20200%20Hz%2C%20etc.)<!--- Categories --->
 == See also ==
 *[[Active noise control]]
-==References==
-{{Reflist|30em}}
 [[Category:Audio engineering]]