Sound Level Meter (1)

Sound Level Meter using Arduino By, R.Rajeswari K.Kiran P.Megavarshini M.Savitha

AIM: To implement sound level meter to measure noise in dB by using Arduino UNO.

Project Objective: • Noise Pollution effects on Living beings. • Human ear audible range : 0 dB to 140 dB. • Slightly expensive meter only available for measuring sound levels in dB.

• It is necessary to monitor sound level and keep it under control for good and long time hearing.

Project Overview : Using a normal Electret Condenser microphone , we will measure the sound level and a normal amplifier circuit is used to amplify the sound signals which will be feed to Arduino to calculate the sound signals in dB.

Hardware Required:

Software Required:

• • • • •

Arduino IDE

Arduino UNO Microphone LM386 10K variable POT Resistors and Capacitors

Total cost = 655/-

COMPONENTS:

ARDUINO UNO: • Arduino UNO is a widely used open source micro controller board. • This board is equipped with sets of digital and analog input /output pins that may be interfaced to various expansion boards and other circuits • The board features 14 digital pins and 6 analog pins. • It is programmed with Arduino IDE (Integrated Development Environment) via USB cable. • UNO is generally considered the most user-friendly and popular board among the other Arduino board series.

Why Arduino Uno? • It is an open source project where software and hardware are extensively accessible. • It is flexible, offers a variety of digital and analog inputs. • It is easy to use • It is inexpensive • It is easy to learn for beginners. • Cross-platform: You can program it on Windows, Linux and several other operating systems.

Arduino IDE  Contains all the software which will run the computer in order to program and communicate with the Arduino Board.  Arduino IDE contains an editor which we can use to write sketches in a simple programming language  Using the IDE the program we wrote is converted to C language and then compiled  When the Arduino board is connected to a computer using the USB cable, by using the IDE we are able to compile and upload to board the program.

Electret Condenser Microphone : It is the most common type of transducer that is used to detect or measure sound signals. It functions exactly as opposite of a normal speaker, that is when a sound signal is detected it produces electrical signals.

How to use Electret microphone: The Electret microphone has two plates inside it.The distance between the plates is directly proportional to sound present in the environment. Recommended operating voltage is 2V but it can withstand up to 10V. Microphone has polarity to make sure you connect the positive (output) terminal to supply through the resistor and the ground terminal to the ground. The resistor R1 (.1K) is used to limit the current flowing through the microphone (maximum should be 0.5mA) .

Continued..

The capacitor C1 (1uF) is used to filter the DC noise that might be coupled along with the analog electrical signals (output). Also, note that the capacitor is also polarity sensitive and the positive should be connected to microphone Output pin. This capacitor is rated for 20Hz to 16,000Hz so any sound waves in that range will be picked up the microphone.

100Ω

Specifications: • • • • •

Dimension: 6 x 3.4 mm Operating Voltage: 2V to 10V Current consumption: 0.5mA (max) S/N ratio : More than 62 dB Operating Frequency: 20Hz to 16,000Hz • Impedance: <2.2kΩ

Applications: • Noise detectors • Voice control modules • Sound recorders

LM386 Amplifier: LM386 is a low voltage audio amplifier and frequently used in battery powered music devices like radios, guitars, toys etc. The gain range is 20 to 200, gain is internally set to 20 (without using external component) but can be increased to 200 by using resistor and capacitor between PIN 1 and 8, or just with a capacitor.. LM386 has a wide supply voltage range 4-12v.

Pin Number

Pin Name

Description

1,8

GAIN

Used to set the gain of the IC by connecting to a Capacitor

2

Input (IN-)

The Inverting pin is normally grounded.

3

Input (IN+)

The Non-Inverting Pin of amplifier is provided with audio signal.

4

Ground

The ground pin is connected to the ground of the system

5

Vout

Provides amplified audio output, connected to speaker

6

Vss/Vcc

Connected to power

7

Bypass

Bypass pin is used for connecting a decoupling capacitor

LM386 Audio Amplifier: The IC consumes very less power and hence can be operated using a 9V battery easily. Volume control and gain control is also possible in this. The IC comes in a 8-pin PDIP package and requires very less components to function hence it is highly easy to use.

How to use LM386 IC: The LM386 only requires a couple of capacitors and resistors to start working. The IC is powered using the pin 6 (typically 5 or 9V) and the ground pin 4 is connected to the ground. The inverting pin (pin 2) is normally grounded and the Non-inverting pin (pin 3) is provided with the Audio signal. This audio signal can be from a microphone . The 10k resistor is added in series with the audio signal to act as a volume control.

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The pin 1 and pin 8 are used to set the gain of the Amplifier. If there is nothing connected between these pins then the default gain will be 20 dB, but we can connect a 10 uF capacitor across it to get the maximum gain of the IC which is 200dB. The pin 7 is used to connect a filtering capacitor (0.1uf) for our amplifier IC to avoid unnecessary oscillations. The amplified audio signal can be obtained from the pin 5 which is connected to a 8ohm speaker through a filtering capacitor. The RC network with 0.05uF and 10k resistor is optional.

LM386 Audio amplifier features and specifications: • Supply Voltage: 4-15V • Quiescent Power: 24mW @ 6V • Analog input voltage 0.4V (maximum) • Voltage Gain: 20 to 200 • PSRR: 50dB • Speaker impedance :4Ω Available in 8-Pin PDIP,SOIC packages.

Applications: • • • • •

AM and FM Radio amplifiers Portable music players Low Power Audio amplifiers Power Amplifiers Audio boosters

Circuit Diagram:

Working Explanation: Condenser microphone(transducer) convert sound into an electrical signal which will be amplified by LM386 audio amplifier and supply it to the analog port of arduino.ADC converts analog signal to Digital value which will be converted to values of dB through regression method.And the LED is made to go high if there is sound recorded above 60 dB. Capacitors

Function

C1

Gain(20-200).

C2

Filter DC noise from microphone.

C3

Filter DC noise after amplification.

Application:  To Measure: • • • • • • •

Noise at work and Occupational noise. Environmental and Community noise. Industrial noise. Airport noise. Mining noise. Traffic noise. Construction noise.

 Vehicle Noise Testing

Future Agenda: • Regression method analysis and calculation. • Code Implementation

References: • https://circuitdigest.com/microcontroller-projects/arduino-soundlevel-measurement • www.bksv.com • www.bestengineeringprojects.com • www.enviroeqipment.com • www.noisemeters.com • www.tutorial45.com • https://components101.com/ics/lm386-audio-amplifier-ic-pinoutcircuit-datasheet. • https://circuitdigest.com/electronic-circuits/lm386-audio-amplifiercircuit • https://components101.com/electret-condenser-microphone