Research And Implementation Of Airborne Voice Call System Based On Improved Spectrum Subtraction

With the rapid development of China’s national economy and aviation industry,the application of military or civilian helicopters is becoming more and more widespread and more and more popular,and has penetrated into various fields of human life.As an important electronic device in the aviation field,the airborne voice call system is crucial for call quality and reliability,and uninterrupted calls.These parameters will directly affect aircraft operation and mission execution.Therefore,more and more attention has been paid to the research and development of airborne voice communication systems.This article uses STMicroelectronics ST’s Cortex-M series of high-performance processors STM32H750 as a micro-control unit,its built-in M7 core frequency up to 400 MHz can meet the needs of real-time voice transmission.Adopt low-power stereo audio codec TLV320AIC3106-Q1 as the audio processing chip,which has a stereo headphone amplifier and can perform multiple inputs and outputs in a single-ended or fully differential configuration,can provide multi-channel audio acquisition and playback Multi-party conference call mode.The work flow of the airborne voice call system is that the audio collected by the microphone is transferred to the micro control unit(MCU)through the audio codec chip,and the input voice is reduced in the main processor.The enhanced voice is transmitted through the RS-485 network Go to each node to play.The noise reduction algorithm uses spectral subtraction based on the noise addition model,which has the characteristics of simple implementation and small amount of calculation.Spectral subtraction uses the principle of spectrum subtraction to subtract the noise spectrum from the noisy speech spectrum,thereby removing noise and achieving the purpose of speech enhancement.But if the amplitude spectrum of the noisy speech is subtracted from the estimated noise spectrum and a negative value appears,it is easy to produce "music noise".In view of this situation,the noise spectrum can be over-reduced to achieve the purpose of reducing the amplitude of the broadband spectrum peak,and sometimes it can even be completely eliminated.In order to solve the problem of network transmission,a time-division multiplexing four-layer communication protocol based on RS-485 bus is designed.The universal multi-device time-sharing multiplexing bus protocol can solve the time-sharing andreliable data transmission of multiple devices in one channel.The method of combining dynamic networking link and static networking mode can solve the problem that the communication of the entire system is paralyzed due to the failure of a single host in the static mode.The airborne voice call system designed in this paper can establish a dynamic synchronization mechanism to prevent data collision,so that nodes in a channel can quickly obtain their own time slices and send the voice data to be transmitted in their own reliable time slices.Through testing,we know that the custom communication protocol can meet the needs of each node to send and receive data.The quality and intelligibility of voice calls reached the national military standard level 3 or above,and the signal-to-noise ratio was significantly improved.At present,the airborne voice call system based on improved spectrum subtraction has been successfully applied to the in-flight call system of a certain military helicopter.It can achieve a barrier-free,clear,high-quality voice call between crew members and achieved the expected results.