Calibration of Mobile Phones to Measure Sound Levels

  • For sound level measuring, we can use a mobile phone. There are many mobile apps. We will use the application Sound meter.

    If we´re measuring the same situation with more mobile phones, we find out that displayed data are different.

     

     

    To create a noise map of the town, we need to use more mobile phones. So we have to calibrate them.

     

    In a big room we put the best sound meter far enough from a speaker and next to it we put a phone which we want to calibrate. The microphones of both devices must be facing the same direction.

    The calibration process:

    1. We will create a tone of frequency 600 Hz.
    2. We will gradually set PC´s volume so that the sound meter shows values of 30, 40, 50, 60, 70, 80 dB
    3. We will note data from the sound meter into a table.

     

    We will put the measured data into LoggerPro program and we will examine which function is suitable for the description of dependance.
    Suitable function:

    Unsuitable function


    For our calibration it is suitable the function y = ax+bx which has parameters a, b
    X- data measured from a phone    Y - real accurate data

     

    For every phone it is important to make a table of measured data and create a special calibrating equation.

     

     


     

    Test

    In conclusion we will test given methods.
    In a room we will create a sound of constant volume.
    We will prepare 2 different phones and we will read shown data. The phones have these calibrating equations:

     


     


    We will input the measured data into calibrating equations and there should appear almost the same results.