A Soundbooster or the Active sound design is an acoustic technology idea used in automobiles to change or enhance sound both inside and outside the car. To create a simulated vehicle sound, active sound design (ASD) frequently employs active noise control and acoustic augmentation techniques.

ASD can be used in a variety of ways, from amplifying or lowering an existing sound to producing a completely new sound. Because there is no single uniform paradigm for ASD, different software or hardware techniques may be used by different car manufacturers. Acura’s Active Sound Control, Kia’s Active Sound System, Volkswagen’s Soundaktor, and QNX’s Acoustic Management System are all names for ASD.

The Lotus Bluebird, which debuted in 1992, was the first vehicle to use active noise cancellation (ANC). Lotus teamed together with Harman International in 2009 to develop an upgraded ANC system that minimized road, tire, and chassis noise. Engine systems have gotten more efficient but less audibly appealing to consumers as the desire for inexpensive and cleaner combustion engine vehicles has grown. The sound of an electric or fuel cell vehicle is high-pitched, unlike a traditional combustion engine. Manufacturers of both combustion and electric vehicles hope to improve vehicle reception by improving the quality of interior and outside vehicle sound with ASD.

Components

Active noise cancellation (ANC) is a software procedure that employs existing in-vehicle infotainment hardware to remove unwanted sounds from a vehicle’s interior. Unwanted audio signals are detected by sensors and filtered out of the overall interior car sound, a technique known as harmonic order reduction. Manufacturers may employ adaptive cruise control (ANC) within a vehicle to mitigate the impacts of ASD.

Engine sound enhancement (ESE) is a technology that allows manufacturers to improve engine noises with synthetic noise created from real-time engine data, such as RPM and torque. This synthetically created sound is sent through the vehicle’s interior or outside speakers. Manufacturers can employ ESE in ASD to improve perceived engine power without having to make the mechanical changes that other techniques might necessitate.

ASD Motivations

Smaller engine subsystems have made interior vehicle noise less pleasant in combustion engine vehicles due to environmental limitations and a drive for fuel economy in the automotive industry. Instead of a recognizable engine sound, electric and hybrid vehicles emit a quieter high-frequency noise that annoys passengers and poses a danger to pedestrians who may not detect an approaching vehicle. Consumer desire for a more appealing interior sound, as well as an identifiable brand identity in both the interior and outside of the car that reduces safety concerns, has risen as a result of these advances.

Traditional iterations of car sound management included time-consuming mechanical changes like balance shafts and sound-deadening material, which increased manufacturing time and cost. Manufacturing costs and complexities are minimized because to the revival of sound design in the form of ASD. Rather than integrating the technology into the engine structure, the sound can be fixed and tailored to the vehicle at a later stage of development.

Variations

To adjust the interior and external noise of the car, active sound design (ASD) uses inputs from engine and vehicle speed, pedal input, exhaust noise, and vehicle vibrations. To obtain the required outputs, these input variables are filtered. ASD variants Choose one or more of these factors to create a new sound. The following are some of the variations:

• Signals acquired directly from the engine output and conveyed in the inside of the car are referred to as passive sound creation.
• Passive and active sound generation: enhancing the vehicle’s outside noise by amplifying the exhaust input and producing a new output.
• Active mounts: take inputs from the outside car and send vibration outputs to the inside.
• Synthetic sound is the creation of a new sound using the internal stereo audio system.

Theory and Practice

Cylinders are responsible for burning gasoline and producing energy to power a standard combustion engine. The periodic firing of these cylinders can be reduced to a series of sinusoidal waves (by conventions of the Fourier transform). The engine crankshaft’s rotations per minute (RPM) and the cylinders’ firing sequence, or arrangement, determine the sine waves. The harmonic orders of engine sound that are lacking from the interior sound can be increased using Digital Signal Processing (DSP) techniques to enrich engine sound in the passenger cabin.

The engine load state is determined by acceleration sensors on older vehicles’ engines, or by the Controller Area Network bus (CAN-bus) in current cars, in order to record the missing orders. The missing orders are passed via dynamic band-pass filters (a device that relays specific frequencies). The signal is routed through cascading high- and low-pass filters to reduce artefacts (disruptive clicks) during transmission. The orders are amplified through the vehicle firewall (body separating the engine from the inside) and interior sound system, using an adaption of the engine’s RPM signal (recorded by an inductive voltage transformer).

Subharmonics and Sound Signatures

Virtual (synthetic) noises are frequently utilized in electric and fuel cell vehicles to compensate for the absence of a combustion engine sound. Manufacturers must understand the psychoacoustic theories behind sound preference in order to build the best sound design in an electric vehicle (EV). Experimental examination contrasted a subjective ranking of sound quality components to J.D. Power’s APEAL study in a study of diesel engine sound quality.

Manufacturers try to lower loudness increment and high-frequency sound for a more pleasant driving experience based on studies of consumer preference in vehicle interiors. The standard vehicle noise is muffled in current EVs by an RPM-dependent low-pass-filtered sound. This low-pass-filtered sound is a synthetic sound with a lower frequency that is dependent on the EV’s actual engine parameters such as speed and load.

The virtual noise is subjected to Alt and Jochum’s simple-integer ratio harmonic order approach. The EV’s original high-frequency components are then separated from subharmonics (lower-frequency copies). [13] Individuals subjectively picked these subharmonics as preferred for the interior sound of an EV after evaluating different generated sound stimuli. [14]

Vehicles with internal combustion engines respond dynamically to varying driving conditions. Manufacturers must consider a sound identity that includes a powerful driving sound when creating a brand sound for an EV. A base sound signature is made up of a series of sub-signatures and micro-signatures that can be enlarged to improve the sound’s dynamic quality. These sub-signatures can be allocated to factors (such as load and speed) or maneuvers that transmit specific sound samples. The sound produced by creating micro-signatures in electric vehicle drivetrains is more vibrant and emotional than the EV’s basic frequencies.

Consumer Reaction Challenges

The introduction of ASD is mostly overlooked by the typical customer. However, the fake engine sound in modern BMW vehicles makes customers feel misled. Many instructional videos and articles about disabling the ASD in BMW vehicles can be found online, as well as articles about the synthetic noise that sounds fake.

For electric and hydrogen fuel cell automobiles, create a unique brand identity.

Typical combustion engine automobiles emit a sound that conveys the car’s brand identity when in operation. The frequency of sound in electric and fuel cell vehicles fluctuates minimally throughout a period of acceleration due to the nature of the single gear system and arrangement of power converters, and is not well suited to the actual state of the vehicle speed and load. Furthermore, the lack of engine noise creates a spectral gap (empty space) between wind and road noise, amplifying individual vehicle components and lowering cabin sound quality.

Manufacturers must choose between recreating the sound of a normal combustion engine or generating a totally unique sound idea when creating a brand identity.

The combustion engine process is being re-created.

Current active sound design implementations in combustion engine cars may not accurately mimic the combustion process’s micro structural fluctuations (variations between cylinder firings). Identifying and recreating the harmonic engine commands is inefficient since the signal waves are generated by numerous periodically firing cylinders. Furthermore, this method implies combustion engine homogeneity. The force generated by the cylinders is periodic and varies from one cycle to the next, making it hard to duplicate the natural component of engine noise.

Examples of use

Several automakers have their own versions of ASD technology.

• By sifting through the auditory data it receives, an engine management system in vehicles like the BMW M5 increases the noises produced by speed and engine power. Drivers can choose a driving mode that affects both the interior acoustics and the vehicle’s performance.
• Similarly, the Kia Stinger has five drive modes (eco, comfort, smart, sport, and custom) that control the volume and harshness of the sound inside the vehicle. This car, which comes with a turbocharged engine, is designed to respond to human preferences. The turbocharger improves efficiency by forcing more compressed air into the combustion engine, resulting in a constant and clean sound.
• A Helmholtz resonator and a sound symposer are used by Porsche to convey engine sounds directly into the vehicle cabin. The Helmholtz universal resonator muffles engine noise by using an electronically controlled valve that oscillates with air, similar to the sound made when blowing over a bottle’s top. The sound symposer is made out of a line of plastic tubing with a membrane and flap valve that function similarly to the human ear. When you hit the Sport button, the resonator and sound symposer fully open, amplifying the engine sound in the car cabin.