Design Of Multifunctional Sound Level Meter Based On STM32F407

As the rapid economic and social development,the construction,transportation,and resident noise has become one of the main problems which influence people’s rest,normal work and life,the noise problem can not only affects the people’s work efficiency,but also influence people’s health.Therefore,It’s very important to develop an accurate sound level meter to help controlling noise pollution.Compared to the noise measurement technology in developed contries,noise measurement in china is rather fall behind.the current domestic market are still selling many analog sound level meter and small amounts of digital sound level meter base on DSP,the analog sound level’s meter accuracy,dynamic range,stability is insufficient,while,digital sound level meter based on DSP,generally use digital filtering method to implement the frequency weighting and octave filter,because of the fixed-point data type’s finite word length and quantify effects,the designed digital filter will be unstable sometimes,also the computational accurary is not high enough.For the urgent need of accurate noise measurement,one kind of multifunctional sound level meter structure composed by floating-point microprocessor STM32F407+ PCM1804 which could meet the grade 1 sound level meter and grade 1 octave filter requirements was presented.in this thesis,we introduced the way to implement frequency weighting,time weighting and octave filter in digital way and the best structure to implement IIR digital filter firstly.Then,we introduced system’s hardware and software design methods,lastly,testing results of the designed sound level meter and measuring error analysis was discussed.Test results shows that the multifunctional sound level meter based on digital filter method can meet the design requirements.its measurement precision is 0.1 dB,linear measurement range is 30～130dB,the machine noise under the A/C/Z weighting is 19.7/20.8/22.9dB respectively,the frequency weighting and linear error meet GB/T 3785.1 2010 requirent for grade 1 sound level meter,octave filter error meet GB/T 3241-2010 to the requirement of grade 1 filter.