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Lotus Engineering & Harman Becker Automotive Systems Active Noise Control - Web Exclusive

Apr 17, 2009
Eurp_0904_01_z+lotus_engineering_harman_becker_active_noise_control+lotus_logo Photo 1/1   |   Lotus Engineering & Harman Becker Automotive Systems Active Noise Control - Web Exclusive

Lotus Engineering, the automotive consultancy division of Lotus Cars has reached an agreement to jointly develop noise management solutions using Lotus' patented Active Noise Control technologies with Harman Becker Automotive Systems, the automotive division of Harman International.

Exclusive rights are granted to Harman Becker to manufacture the latest technology solutions for the worldwide vehicle OEM market. The agreement includes all of Lotus' Active Noise Control technologies comprising Road Noise Cancellation, Engine Order Cancellation, and Electronic Sound Synthesis.

The Road Noise Cancellation and Engine Order Cancellation systems will provide vehicle manufacturers with the ability to improve in-cabin refinement. They operate by reducing both overall noise levels and specific audible frequencies, which may be unpleasant in the cabin space. Electronic systems determine the signal needed to provide cancellation, which is then seamlessly generated through the in-car entertainment system. The result is a quiet, controlled environment, free of intrusive noises.

External Electronic Sound Synthesis provides specified electronic sound models, which can be applied to an external speaker system to improve pedestrian safety. This is especially important for electric and hybrid vehicles, which can be difficult to hear at lower speeds due to their drive mechanism. A synthesised sound, dependant on speed, is projected from speakers at the front and rear of the vehicle, making it instantly recognizable that the vehicle is in motion.

Internal Electronic Sound Synthesis allows sound contouring in the cabin, enhancing the driving experience by creating engine speed and throttle dependant sounds audible through the in-car entertainment system. The system delivers audible feedback to drivers even when the engine is silent or, alternatively, it can be used to reinforce an OEM "sound DNA" to the end user.

Harman International, the high-end infotainment systems provider, will be the production system integrator and supplier, and will work with vehicle manufacturers on model-specific system architecture options.

Lotus Engineering, which has over 20 years of experience in Active Noise Control technologies, will assist manufacturers with system performance optimization. The result of the Lotus and Harman International technology collaboration will be to generate Active Noise Control solutions available to vehicle manufacturers in all markets. Working systems are ready for production implementation and manufacture. The introduction of affordable noise management systems offers multiple benefits to manufacturers and consumers alike, achieving eco-friendly optimization of vehicle weight reductions and improved CO2 emissions.

The Lotus suite of patented Active Noise Control technologies comprises three main systems, each of which can be used individually or in combination.

The first two systems are Road Noise Cancellation (RNC) and Engine Order Cancellation (EOC). Both of these attempt to reduce noise levels in the cabin, particularly at frequencies that are audibly unpleasant. In the case of RNC, the system reduces broadband noise levels at frequencies below 250Hz, whereas EOC tackles harmonic frequencies generated by ignition events in the engine. Input signals from the engine (for EOC) or sensors mounted to the suspension system (for RNC) are fed into the electronic controller, as are sound signals, measured by microphones located in the cabin.

The software algorithms of the controller then calculate what sound is needed to provide cancellation and the speakers of the in-car entertainment system are used to put this into the cabin. All this takes just a few thousandths of a second and repeats and adapts constantly through the complex control system, seamlessly and instantaneously adapting to changes in speed or road condition. The cancellation system operates on the input signals so other noise in the vehicle such as the audio system and speech are not interfered with or cancelled. The result is a quieter, more pleasant cabin.

The third system is Electronic Sound Synthesis, which has applications internally and externally. Internally, Electronic Sound Synthesis enhances the sound in the cabin. The control system uses engine speed signal, a throttle position sensor and the in-car entertainment system to add sound. In this way a car could be made to sound sportier or be given the pleasing sound characters of, say, a flat-6 or V8 engine. Coupled with EOC and RNC, the interior sound in the cabin can be tuned to enhance the driving experience and match the brand attributes of the vehicle.

When applied externally, Electronic Sound Synthesis provides engine sound for hybrid or electric vehicles. To synthesize the engine sound, a road speed signal is taken from the vehicle and a waterproof loudspeaker system is positioned behind the grille allowing the sound to emanate from the front of the vehicle. The sound can also be synthesized from the rear of the vehicle in the same way, allowing warning when the vehicle is reversing.

When a car is operating on the electric motor only, throttle and speed dependent synthesized sound projects an engine sound in front of the vehicle. The technology was designed around the behavior of a conventional engine, using an existing engine sound which makes it instantly recognizable with the pitch and frequency helping to identify vehicle distance and speed. If the hybrid's engine starts operating, at higher speeds or throttle demands or lower battery levels, the control system automatically stops the external synthesis. When the powertrain control system switches the car back to running on the electric motor only, the synthesis controller instantaneously sets the system running again. It is all completely automatic and the driver hears almost none of the additional sound.

In order to generate a realistic engine sound, recordings of a suitable donor engine are made and analyzed to establish the characteristic frequencies at different engine speeds. These frequencies are then entered into the synthesis controller in the form of a "voice" which outputs the sound through an amplifier and the loudspeakers. Alternatively, more futuristic sounds for electric vehicles can be created using sampled sounds and generated waveforms.

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