# Case 09: Noise Detection Device in the Library


##  Introduction 
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- Noise has always been a serious problem in library management. If you stay in an environment above 85db for more than 8 hours, it will damage the hearing ability, although under normal circumstances the library will not have such a large source of noise , but the impact to readers from smaller noise cannot be ignored in the library . Thus, we can make a library noise detection device to remind people of the current environmental noise level.


##  Function
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- Detect the noise level from the sound sensor on the micro:bit and have the value displayed on the OLED screen, program to light on the LED with the equivalent color. 

## Products Link
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- 1 x [microbit Smart City Kit](https://shop.elecfreaks.com/products/elecfreaks-micro-bit-smart-city-kit-without-micro-bit-board?_pos=1&_sid=ce30b50b6&_ss=r)

## Picture
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![](./images/microbit-Smart-City-Kit-case-01-02.png)

## Hardware Connection
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Connect the green led to P1, the yellow to P2, the red to P9 and the OLED to the IIC  port on IoT:bit. 

![](./images/microbit-Smart-City-Kit-case-04-03.png)

## Software Program

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Click "Advanced" in the MakeCode drawer to see more choices. 

![](./images/microbit-Smart-City-Kit-case-01-04.png)

For programming, we need to add a package: click "Extensions" at the bottom of the MakeCode drawer and search with "iot-environment-kit" in the dialogue box to download it. 

![](./images/microbit-Smart-City-Kit-case-01-05.png)



***Notice:*** If you met a tip indicating that some codebases would be deleted due to incompatibility, you may continue as the tips say or create a new project in the menu. 

## Program

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Initialize the OLED and display the sound level on the OLED screen. 

![](./images/microbit-Smart-City-Kit-case-09-07.png)

If the sound level is below 100, program to light on the green led, if it's below 150, program to light on the yellow led; or to light on the red led. 

![](./images/microbit-Smart-City-Kit-case-09-08.png)


Link: [https://makecode.microbit.org/_2D82PVTC2Vhr](https://makecode.microbit.org/_2D82PVTC2Vhr)

<div style="position:relative;height:0;padding-bottom:70%;overflow:hidden;">
<iframe style="position:absolute;top:0;left:0;width:100%;height:100%;" src="https://makecode.microbit.org/#pub:https://makecode.microbit.org/_2D82PVTC2Vhr" frameborder="0" sandbox="allow-popups allow-forms allow-scripts allow-same-origin">
</iframe>
</div>  


## Result
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- Different LEDs are lightened in accordance with the equivalent sound level.