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:
- We will create a tone of frequency 600 Hz.
- We will gradually set PC´s volume so that the sound meter shows values of 30, 40, 50, 60, 70, 80 dB
- 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.