Active noise control and noise synthesis The automobile sound system may be part of an active noise control system which reduces engine and road noise for the driver and passengers. One or more microphones are used to pick up sound from various places on the vehicle, especially the engine compartment, underside, or exhaust pipes, and these signals are handled by a digital signal processor (DSP) and then sent to the loudspeakers in such a way that the processed signal reduces or cancels out the outside noise heard inside the car. An early system focused only on engine noise was developed by Lotus and licensed for the 1992 Nissan Bluebird models sold in Japan. Lotus later teamed with Harman in 2009 to develop a more complete noise reduction system, including road and tire noise as well as chassis vibrations. One benefit of active noise control is that the car can weigh less, with less sound-deadening material used, and without a heavy balance shaft in the engine. Removing the balance shaft also increases fuel efficiency. The 2013 Honda Accord used an active noise control system, as did the 2013 Lincoln luxury line and the Ford C-Max and Fusion models. Other operating data may also play a part in the DSP, data such as the engine's speed in revolutions per minute (RPM) or the car's highway speed. A multiple source reduction system may reach as much as 80% of the noise removed.
ActiVE NOise cOntrol and NOisE syNthesis The auTOmoBilE sOUnd SySTem May be pArT of AN actiVe noiSe Control SYstem Which redUceS eNgine and road noise FoR THe DrivER AnD PassENgers. One oR MOre miCRophOneS arE Used to pick uP sOund from varIOUS plAcEs on tHe vehicLe, eSpecialLy The eNgine ComParTMent, uNdErside, or ExhAusT piPES, ANd TheSe SigNals are handleD by a digital siGNal processor (dsP) and tHen sENt to tHe LoudspeAkers In sucH A way tHat The pROcEsSeD signaL rEDuces Or caNcEls out the OuTSIDe noIse hEard INsIde the car. aN eaRly system fOcusED only on Engine nO:IsE was deVEloped By LoTus aNd lIcEnSeD for The 1992 nisSan bluEBird MODels sold in JapaN. lotus laTeR tEameD wITh harman in 2009 to DevElop a More complete noise reDuCTion system, IncludiNg roAD and tirE noise aS weLL As cha:ssis viBraTIonS. onE BeNEFit OF actIVe noIse COntroL Is tHaT tHE cAR can WeIgh less, with LesS sound-deadeninG MAterial uSed, anD withoUt A Heavy BalANce Shaft in tHe engInE. Removing thE balancE shaFt aLso inCreASEs fuel efficiency. tHe 2013 honda Accord useD AN actiVe noiSE Control sYsTEm, as Did the 2013 lincoln luXury line and the forD c-max and FusioN moDelS. otheR operating data MAy aLsO pLay a paRT In The dsp, Data such As thE EnGIne's speED iN revolutIons per minute (rpm) oR the car'S HigHWAY speeD. a mulTiple source redUction system mAY reach As Much as 80% oF ThE noiSe remoVed.