For sound level measuring, we can use a mobile phone. There are many mobile apps. We will use the application Sound meter.
![](https://lh3.googleusercontent.com/AaHq72N3_j2nx5Xx-usKSTzzafj7vx_OU8sxfGN-xlSOCNGqKDUrZMYa6QY6S7gaSgVS9d9-DKNfq2JAJfAQWHjhcqbtGJp5tYjL1kJD0cN8-rkaqmFqZfKdDCpYhHqMRvqQFNlA)
If we´re measuring the same situation with more mobile phones, we find out that displayed data are different.
![](https://lh3.googleusercontent.com/ruQ4GvFmT5UhUV4ZVBMipfwZ_xb6BTtnMkknFv7516aYImDcmKGlYCXgkITdxvf2a5-t8BsvqsGPn4nJsE-y8HdtJOSVbX5PzfHsa68Ad9vGDt80kvRCDp7OlddGbDyYJuapdV9u)
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.
![](https://lh5.googleusercontent.com/8gA7NGKti23ITwgFq0DsFD0wmIhlvHxYmC0aZsmHGLYh3dD2I8BEQMzWFVEuvssrT-zC8PQIA2ZrOrydbPI4n-pqvwk75_ontJk6cCKYfGTP83ScwpN0Ld9AePXOD0JaOzxhU-Hj)
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.
![](https://lh3.googleusercontent.com/ZA4oaCI69RH2vQl083ouZuh77YxDg2iV7D9WfBkA9Obe76b020i8LLaxjNPuGuqMbra1-WaFIWVVSpHigJQMcNJ51E-0wgWSCppmniMItJ9N3W0iLJXAmg83QXQuuErbVE2owhen)
We will put the measured data into LoggerPro program and we will examine which function is suitable for the description of dependance.
Suitable function:
![](https://lh6.googleusercontent.com/zQEL0ArxM71Cta9a3JGIm8u9REJgeR0GbkkvWVaXp8DgxspHG9HZ-uGX1sgCfUsa4PGIfbP-WT_T4yUNKicSECrw4PN0tavDBNtarC2-2bLXOCfhQ79gjXny_ZhsMD2Kle3PgNZn)
Unsuitable function
![](https://lh4.googleusercontent.com/n9QusBJqfFID4EYbft_MnuxG6Qo0EO1F1H7qcHRspMREmI0WwfGWfDjeUPF6Ypw2VfNat6pccSHHVkkUCeCdFj1vlknoHnOKhsRsBZEwPK2agcS-6vyq8STih4J80cPLLBQy3Im8)
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
![](https://lh4.googleusercontent.com/qRiCTqP4CEk0DTIa3PzumJspHDyWgmhSlvN3MIIq3qxo2IexEg4bBHQ6K1Gh022O5lKhdA9Yacw70RU3rc5ClzEvdkhhDDMCje72l0aKruRsVX5o5fyPnz55Qk4Y5zLyW049ynjR)
For every phone it is important to make a table of measured data and create a special calibrating equation.
![](https://lh5.googleusercontent.com/mRtYxKFcuz9elox9ic3Ht8f1uKOHZjVyce9Q3bT9d4nu2jMb8ZtElCUDJogkY27re0zU-JizUdbu06JFOlldC_cEYdesZN2iFqG6Idlo0GMrrSifbciiCBkMY6_Tqisqqgx7Na4i)
![](https://lh3.googleusercontent.com/ZA4oaCI69RH2vQl083ouZuh77YxDg2iV7D9WfBkA9Obe76b020i8LLaxjNPuGuqMbra1-WaFIWVVSpHigJQMcNJ51E-0wgWSCppmniMItJ9N3W0iLJXAmg83QXQuuErbVE2owhen)
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:
![](https://lh3.googleusercontent.com/Y3bn-lNP84CU16N8BWI7GuDPjyfN-1dTas5m9J7V-bls8L3GI-OCVkvbV8nbstSUSQmaPWAVccWsz8p4iXImRWxTsna_m6qPYFc3NozfN0jQkIXqiorThxEQNPlXvwE2XKw2i-MW)
We will input the measured data into calibrating equations and there should appear almost the same results.
![](https://lh6.googleusercontent.com/aiu8UaX1oxoUcKu2cbrX_Esjl7UmIPPhxm9tYbSUj4KTbyYdNNKpjst_OvB-eXgW6Yz4vrYBxGmgUVqb78j0MfqXQzyM1dMAzcd07zvwVMSKOXf_qPfDYYbkex2tqHEKILwWGB0z)
![](https://lh4.googleusercontent.com/uA35jKxH7kgtd1Z1nimA4OfCDoOEBe0ZxigJ5uBTD4rKidKdB1JQzSJYWuXMHaT2dAYtEk0Rh0vc2cI5qwRTbqvaWdJq6MzDGGoQQLfU9F1nr27A0cCm3F89tXojatKlMiY_mfmQ)
![](https://lh3.googleusercontent.com/eBJj3tAbSZi9SVYR5UrUC2plgptdxA5fbHU84c0pTUxw-kTqPmbEZ_3xO5lmbKXQuhW-6fUzwGlyI_Cx_FQdsuk5ZF7-TdJThcZMnl88ZgMyrQks5ET93XnKDE0F2ZAcMPhaUrg1)
![](https://lh6.googleusercontent.com/-Q4EMcHCbOO7oziXXK7CoijmulbTnuYwnzkxskdh3D6kJ9mMuBKs8y8ZJJeL9zqmlaNx_wZ9-QZpGFcQUcJqHqrtrL2OqPNDutVFTs00lAHRFsoNwY3iG6FBRtPinrGLNf2LGTHC)
![](https://lh6.googleusercontent.com/uRqdUBeHTgvhPDBvz0yjY0xkJBE61MKHS7XybUW01oDiODBR7P7bWO01E_3sq28cl7eg9AUXBwado0HIjU-VGh7TC9Kps9v6cOArFKxi-aIwIM_F4aeAwgAS2TP_-hRjMw-xPABx)
![](https://lh3.googleusercontent.com/LAf_KcRv673wny2IffpYtlkuruBuoI3NrsJRefZwYQjMKsdMPM49MoVBcx7GfCZR4U01_zleu-uckkFhzQ4851SEFh0b9qr9aA_gJNaLOSlXEIrVnJXKeYAcB7JBd9OPFhTy4bIr)