Electronic components supplier Siemens VDO Automotive claims that active control of a vehicle#;s engine sound significantly influences the driver’s enjoyment and comfort levels.
Research to develop the company’s Active Noise Control (ANC) technology has identified what engine frequencies increase driving enjoyment levels, Siemens says.
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Vehicle makers wanting to identify both desirable and undesirable engine sounds are increasingly turning to the relatively new field of scientific acoustic study.
“For example, preliminary studies show low and constant sound levels are not always preferred,” said Siemens VDO Automotive project manager Dr. Marcus Lewis.
“Harmonious sequences of tones are particularly popular. In fact, motorists make similarly high demands on a good engine sound as they do on a symphony.”
Since even the best designed engines cannot completely eliminate resonance, the company has developed ANC technology which actively influences engine sound at its source with a loudspeaker installed in the air intake system to generate opposing frequencies.
Lotus has demonstrated similar technology in the past to reduce road- and drivetrain-generated vehicle interior noise levels.
“The system works off the physical phenomenon of interference,” Siemens#; Lewis said.
“When two sound waves meet, their amplitudes are superimposed on one another and a new tone is generated with a different volume. In some cases, the waves cancel one another out completely, creating silence.”
Siemens VDO Automotive conducted North American ANC field tests that indicated that most people prefer silence only when driving their vehicles in situations requiring increased concentration, such as at night or during poor weather.
However, harmonious tone sequences seem to be favoured during daytime leisure driving, while harmonics emphasising the acceleration phases are preferred during in-town driving.
In addition to a speaker, the patented ANC concept uses a microphone, also mounted in the air intake system, to continuously monitor and measure sound levels at set driving situation-related points.
An electronic controller calculates the corresponding tone sequence, which is delivered to the intake system by the speaker.
The entire ANC system only requires a few watts to operate, due to its close proximity to the sound source.
The ANC approach allows vehicle manufacturers to more freely manipulate and design engine sound to match the character or branding of a vehicle model or platform.
BMW did this in the early 1990s with careful tuning of exhaust system design and gas flow patterns after research showed, while the German company was developing a range of new V8 petrol engines, that customers preferred a distinctive ‘V8 beat#; to the engine note.
The engineers were surprised to find that customers wanted more to hear more of an engine note than the designers originally thought desirable in a new-generation range of cars and engines.
Siemens says that ANC also increases the rated output of an engine by eliminating the need for passive filters and resonators that hinder the flow of natural air intake.
