DSP Implementation Of Broadband ANC System Of Duct Fan

Noise pollution is widespread in people’s production and life.People who have been exposed to noise for a long time will not only suffer from hearing impairment,but they are also prone to psychological problems.In addition,the noise in some work scenes may also interfere with language communication,affect work efficiency,and even cause unforeseen accidents.In industrial scenes,duct fans are widely used for ventilation in factories,mines,tunnels and buildings.In daily life,fans are also inseparable from automobiles,air conditioners,and household range hoods.At the same time,the hazard of fan noise is also high,often with higher sound pressure level and longer duration.It is of practical significance to study how to effectively suppress fan noise.For fan noise,most of the traditional control methods are passive noise control,such as installing muffler devices at the air outlet and air inlet of the fan,or adding noise barriers to the overall fan equipment to isolate the noise.In addition to its poor suppression of low-frequency noise,fan passive noise reduction has many shortcomings.For example,the installation of noise suppression devices at the air outlet and air inlet of the fan will affect the air inlet and outlet of the fan and reduce the efficiency of the fan.In order to compensate for the reduced work efficiency,the power of the fan had to be increased,which greatly increased the energy loss.In addition,if the overall noise barrier method is adopted,a large volume of noise reduction material is required,which is expensive.The active noise control method is based on the principle of sound wave cancellation,has the advantages of small size,relatively low cost,and hardly affects the operation of the fan,and has a good suppression effect on low-frequency noise.However,at present,the active noise control method is mostly used in the field of earphones,and the application in duct fans is less.In addition,traditional active noise control is mostly implemented by analog circuits,and the ability to cope with changing systems is weak.As the calculating ability of the chip increases,adaptive active noise control using digital signal processors becomes possible,but compared with analog circuits,digital methods introduce higher delays,especially for compact structures,smaller spaces and shorter distances.In the pipeline,the active noise control method is limited by the causality of the system,and the effect is not ideal.Aiming at the application scenarios of duct fans,this paper uses active noise reduction methods to make up for the lack of passive noise reduction.At the same time,the practical application of active noise reduction in duct fans with a relatively compact structure is studied.The research content mainly includes the following aspects:1)The research analyzes the principle of fan noise and its noise characteristics,the propagation characteristics of fan noise in the pipeline,the influence of various parameters of the pipeline on the sound field in the pipeline,and the causality restriction of the feedforward ANC system.In view of the above research,a preliminary design of the active noise control system of the duct fan is carried out,including the position of the microphone and the loudspeaker in the duct and some details of the layout.2)The hardware peripheral part.Due to mainstream development platforms,such as Tronlong’s TL138/1808/6748-EVM development board,the digital signal processor(DSP)chip used is Texas Instruments TMS320C6748,and it is also equipped with an AIC3106 audio chip,which has a high circuit delay and is not suitable For the application of active noise control.In view of this problem,select the appropriate audio chip AD73311,redesign the circuit,write the driver and debug.3)Software design part.After completing the low-latency hardware design,the algorithm needs to be implemented on the hardware platform.In the algorithm implementation process,according to the actual application,a DC bias processing module and a divergence detection module are also added.Finally,the duct fan platform,software,hardware,and algorithm are combined to build an adaptive active noise control system for actual duct fans.The function and algorithm are verified,and the current results and existing problems are based on this.Carried out analysis and outlook.