Noise Reduction Design And Implementation Of The Aero Inner Communicators

Aero inner communicators(abbreviated to AIC)is one important part of the avionics system.It mainly achieves the internal communication in crews of airplane,and completes external communication by controlling the HF,VHF radio and SATCOM.At the same time,by the AIC,pilot can monitor the audio signals provided by the navigation devices of the avion(such as compass,beacon,altimeter etc.).As the audio terminal,AIC must have good call quality,which is related to whether the flight crew complete a given task successfully.With the development of aviation industry in our country,the technique using in AIC has been gone through from the analog processing technology to the digital processing technology with the RS485 bus and Ethernet bus.The digital AIC solves the problem that analog AIC is easily disturbed.Meanwhile,noise reduction technology used in AIC also has been developed from using the DNR simulation method and ASIC special noise reduction chip to using single channel speech spectral subtraction with DSP.The communication quality of AIC has been improved in a certain extent.As the AIC produces some noise by itself,noise reduction still needs to be further improved.On the other side,the comfort of communication also needs to be enhanced especially in the strong noise cabin environment.In this paper,through analyzing the noise sources of AIC,besides using noise cancelling headphones to improve voice clarity,we mainly reduce noise of the machine from three aspects:the noise reduction circuit design,which reduces the noise in the stages of product circuit design,minimizes the impact of circuit noise;using the Voice Squelch to suppress the voice channel noise;using speech enhancement algorithm to reduce the environmental noise,and improve the voice quality of machine.In these aspects,we analyze the commonly used methods and propose some improving measures.And the corresponding experimental results are given.By improving and optimizing the circuit design,the signal-to-noise ratio increased 6 dB when the headphone background noise is the 2.3 mV;using the relative magnitude determination method,the mute switch method and picking up the dynamic background noise,it achieves a more effective muting effect;the speech enhancement algorithm combining multiple algorithm make SNR greatly increased.Finally,we introduce the comprehensive noise reduction processing method.It achieves noise reduction,and has been tested with the related military standards.