Room Noise Detector

Chapter 1

Introduction to Room Noise Detector

1.1 IntroductionUnwanted sound is considered as the noise pollution which can cause both behavioral and health

problems in human beings. Noise pollution can cause Physiological changes in the body like

hypertension, high stress level, sleep disturbances etc. Normal pleasing sound level is around 30

dB but the normal environmental noise is around 40-60 dB which can be considered as normal.

But if the noise level increases above 80dB, it can affect our psychomotor performance and

creates high stress level, loss of attention, Physiological changes etc. Over exposure to high

intensity affects the hearing ability of many animals. Very high sound causes the reduction in the

number of animals in the habitats leading to habitat loss and may lead to extinction of species.

Noise interferes with the use of their own sound for communication related to reproduction and

migration.

Noise level above 70 dB can increase the risk of cardiovascular problems due to hypertension,

increasedCortsol production etc. Elevated noise can cause arterial constriction leading to

elevated blood pressure and reduced blood flow. Annoyance due to very high sound increases

the Adrenaline level which is the most important reason of arterial constriction and elevated

blood pressure. Other effects include fatigue, headache, gastric problem etc.

A sensor is a device capable of registering a specific substance or physical phenomenon.A

detector is a device that measures a physical quantity and converts it into a signal which can be

read by an observer or by an instrument. There are various kinds of detectors like temperature

detector (Thermocouple), light detector (LDR), sound detector (microphone), etc. Scrutinizing

Room Noise Detector: This circuit keeps a tab on the noise levels in a room usingdetectors like

microphone, and displays output in the form of blinking LED’s. It can detect threethreshold

levels – 50, 70, 85 dB. A three array LED just makes the output look magnificent.

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1.2 Aim of the ProjectUsually, small-scale and large-scale factories do not have systems to inspect noise levels.

Thehigh expenditure to acquire such devices from the current competitive market makes them

shy off from installing such systems. Also they have some physical constraints such as – cannot

bear

heat, heavy mechanical pressure, etc.

Keeping a view of these shortcomings, this project aims at providing a rugged and cost effective

detector circuit assembled using low-cost components with the intention of substituting

thecurrent commercially existing versions. This project aims at giving a highly accurate output

thus

providing a good calibration of the level of noise in the room.

1.3 Basic DetectorsA detector is a device which receives and responds to a signal or stimulus. Here, the

term"stimulus" means a property or a quantity that needs to be converted into electrical

form.Hence, detector can be defined as a device which receives a signal and converts it into

electrical form which can be further used for electronic devices. A detector differs from a

transducer in the way that a transducer converts one form of energy into other formwhereas a

detector converts the received signal into electrical form only.

A good detector obeys the following rules:

Is sensitive to the measured property.

Is insensitive to any other property likely to be encountered in its application.

Does not influence the measured property.

A sound detector has its measurement calibrated in decibels (dBs).

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Room Noise Detector

Chapter 2

Basic theory

2.1 Introduction:

Noise means any unwanted sound. Noise is not necessarily random. Sounds, particularly loud

ones, that disturb people or make it difficult to hear wanted sounds, are noise. For example,

conversations of other people may be called noise by people not involved in any of them; any

unwanted sound such as domesticated dogs barking, neighbours playing loud music, portable

mechanical saws, road traffic sounds, or a distant aircraft in quiet countryside, is called noise.

Acoustic noise can be anything from quiet but annoying to loud and harmful. At one

extreme users of public transport sometimes complain about the faint and tinny sounds

emanating from the headphones or earbuds of somebody listening to a portable audio player; at

the other the sound of very loud music, a jet engine at close quarters, etc. can cause permanent

irreversible hearing damage.

Sound intensity follows an inverse square law with distance from the source; doubling

the distance from a noise source reduces its intensity by a factor of four, or 6 dB.

Presence of Unwanted and excessive noise is called noise pollution. Noise pollution is the

disturbing or excessive noise that may harm the activity or balance of human or animal life. The

source of most outdoor noise worldwide is mainly caused by machines and transportation

systems, motor vehicles, aircraft, and trains. Outdoor noise is summarized by the word

environmental noise. Poor urban planning may give rise to noise pollution, since side-by-side

industrial and residential buildings can result in noise pollution in the residential areas.

The Indoor noise is caused by machines, building activities, music performances, and especially

in some workplaces. There is no great difference whether noise-induced hearing loss is brought

about by outside (e.g. trains) or inside (e.g. music) noise.

High noise levels can contribute to cardiovascular effects in humans, a rise in blood pressure,

and an increase in stress and vasoconstriction, and an increased incidence of coronary artery

disease. In animals, noise can increase the risk of death by altering predator or prey detection and

avoidance, interfere with reproduction and navigation, and contribute to permanent hearing loss.

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2.2 Unit of Sound:

Decibel (dB) is the unit used to measure the intensity of sound. Decibel is considered as a value

between two powers rather than a specific unit. It is the logarithmic unit used to describe a ratio.

The ratio may be power, sound pressure, voltage or intensity or several other things. ‘0 dB’

occurs when the measured intensity is equal to the reference level ie, it is the sound level

corresponding to 0.02 mpa. In this case, sound level is,

20 log (P measured / Preference) = 20 log 1 = 0 dB

0 dB does not mean no sound ; it means a sound level where the sound pressure is equal to that

of the reference level. It is also possible to have negative sound levels. For example, -20 dB

means a sound with pressure 10 times smaller than the reference pressure. That is 2 kPaSound

pressure level is given in units of dB(A) or dBA. Sound pressure level on the dBA scalar is easy

to measure and is therefore widely used. For sound pressure level, the reference level, (reference

level for air) is usually chosen as 20 micropascals (20 kPa), or 0.02 mPa.

Some of the common sound levels in terms of decibel are,

1. Weakest sound 0 dB

2. Silent environment with natural sound 30 dB

3. Normal human conversation 60-70 dB

4. City with heavy traffic 80-90 dB

5. Drilling or grinding machinery 90-110 dB

6. Jet aircraft & explosion 140-150 dB

2.3 Effects of Noise on Human Body

Noise pollution affects both health and behavior. Unwanted sound (noise) can damage

psychological health. Noise pollution can cause trouble, hypertension, high stress levels, tinnitus,

hearing loss, sleep disturbances, and other harmful effects. Furthermore, stress and hypertension

are the leading causes to health problems.

Sound becomes unwanted when it either interferes with normal activities such as sleeping,

conversation, or disrupts or diminishes one’s quality of life.

Chronic exposure to noise may cause noise-induced hearing loss. Older males exposed to

significant occupational noise demonstrate more significantly reduced hearing sensitivity than

their non-exposed peers, though differences in hearing sensitivity decrease with time and the two

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groups are indistinguishable by age 79. A comparison of Maaban tribesmen, who were

insignificantly exposed to transportation or industrial noise, to a typical U.S. population showed

that chronic exposure to moderately high levels of environmental noise contributes to hearing

loss.

High noise levels can contribute to cardiovascular effects and exposure to moderately high levels

during a single eight-hour period causes a statistical rise in blood pressure of five to ten points

and an increase in stress, and vasoconstriction leading to the increased blood pressure noted

above, as well as to increased incidence of coronary artery disease.

2.4 Effect of Noise on Wildlife

Noise can have a detrimental effect on wild animals, increasing the risk of death by changing the

delicate balance in predator or prey detection and avoidance, and interfering the use of the

sounds in communication, especially in relation to reproduction and in navigation. Acoustic

overexposure can lead to temporary or permanent loss of hearing.

An impact of noise on wild animal life is the reduction of usable habitat that noisy areas may

cause, which in the case of endangered species may be part of the path to extinction. Noise

pollution has caused the death of certain species of whales that beached themselves after being

exposed to the loud sound of military sonar, (see also Marine mammals and sonar).

Noise also makes species communicate more loudly, which is called Lombard vocal response.

Scientists and researchers have conducted experiments that show whales' song length is longer

when submarine-detectors are on. If creatures do not "speak" loudly enough, their voice will be

masked by anthropogenic sounds. These unheard voices might be warnings, finding of prey, or

preparations of net-bubbling. When one species begins speaking more loudly, it will mask other

species' voice, causing the whole ecosystem eventually to speak more loudly.

Marine invertebrates, such as crabs (Carcinusmaenas), have also been shown to be impacted by

ship noise. Larger crabs were noted to be impacted more by the sounds than smaller crabs.

Repeated exposure to the sounds did lead to acclimatization.

European Robins living in urban environments are more likely to sing at night in places with

high levels of noise pollution during the day, suggesting that they sing at night because it is

quieter, and their message can propagate through the environment more clearly. The same study

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Room Noise Detector

showed that daytime noise was a stronger predictor of nocturnal singing than night-time light

pollution, to which the phenomenon often is attributed.

Zebra finches become less faithful to their partners when exposed to traffic noise. This could

alter a population's evolutionary trajectory by selecting traits, sapping resources normally

devoted to other activities and thus leading to profound genetic and evolutionary consequences.

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Chapter 3

Block Diagram &Components Used

3.1 Block Diagram :

Fig3.1: Block Diagram of Noise Detector

3.1.2 Explaination of the Block Diagram :

Step 1: The input of the circuit is given via a microphone. The required signal or sound is given

to the circuit via a microphone, which convert the sound signal to it’s equivalent voltage level to

compare the input sound with the identified threshold voltage.

Step 2: The threshold voltage is the equivalent voltage of sound signal beyond which the input

sound signal will be considered as noise. The threshold voltage is adjusted by adjusting the

resistor value, which inturn adjust the voltage drop across the resistor.

Step 3: The comparator is an op-Amp in which the threshold voltage is applied to it’s one

terminal and input sound signal is applied to another terminal. If the input sound signal is less

than the threshold signal then the output of the comparator will be zero. If the input is higher

than the threshold voltage then the output of the comparator will be high. Which will indicate the

presence of noise.

Step 4: The indicator is a device, which indicate the higher value of comparator. LED, buzzer

can be used as indicator.

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3.2 List of Component Used :

Serial

No Components Specification Quantity

1 Op-Amp IC LM358 1

2 Capacitor 1000µF,100µF,.01µF 1,2,1

3 Silicon Diode IN4007 2

5 Resistor 100k, 47k, 1k, 470Ω, 220Ω 1, 1, 1, 2, 1

6 LED - 3

7 Transistor (0-10)k 1

Table 3.2: Components used

3.2.1 Op-Amp IC (LM358) :

These amplifiers have several distinct advantages over standard operational amplifier types in

single supply applications. They can operate at supply voltages as low as 3.0 V or as high as 32

V, with quiescent currents about one−fifth of those associated with the MC1741 (on a per

amplifier basis). The common mode input range includes the negative supply, thereby eliminating

the necessity for external biasing components in many applications. The output voltage range also

includes the negative power supply voltage.

Fig3.2.1: LM358

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Fig: Internal circuit diagram of LM 358

Features

• Short Circuit Protected Outputs

• True Differential Input Stage

• Single Supply Operation: 3.0 V to 32 V

• Low Input Bias Currents

• Internally Compensated

• Common Mode Range Extends to Negative Supply

• Single and Split Supply Operation

3.2.2 Capacitors :

The capacitor’s function is to store electricity or electrical energy. The capacitor also functions

as a filter passing alternating current (AC) and blocking direct current (DC).The symbol is used

to indicate a capacitor in a circuit diagram. The capacitor is constructed with two electrode plates

facing each other but separated by an insulator. When DC voltage is applied to the capacitor an

electric charge is stored on each electrode. While the capacitor is charging up, current flows. The

current will stop flowing when the capacitor has fully charged.

Disc Capacitor Electrolytic Capacitor

Different kinds of capacitors use different materials for the dielectric.

Different kinds of capacitors are as follows :

Electrolytic capacitors(electro chemical type capacitors)

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Fig3.2.2.1

Tantalum capacitors

Ceramic capacitors

Fig:3.2.2.2

In Disc capacitors, only a number is printed on its body so it is very difficult to determine its

value in PF, KPF, uF, n etc. In some capacitor, its value is printed in uF eg.0.1 in some others

EIA code is used e.g. 104.

One or two numbers on the capacitor represents value in PF e.g. 8 = 8PF

If the third number is zero, then the value is in P e.g. 100 = 100PF

If the capacitor has three numbers and the third number is not a zero, it represents the number of

zeros after the first and second digits e.g. 104 = 10 – 0000 PF

If the value is obtained in PF, it is easy to convert it into KPF or uF

PF / 1000 = KPF or n

PF / 10, 00000 = uF

For example, if the capacitor is 104, then it is 10-0000 PF or 100 KPF or n or 0.1 uF

Multilayer ceramic capacitors

Polystyrene film capacitors

Electric double layer capacitors(super capacitors)

Polyester film capacitors

Poly propylene capacitors

Mica capacitors

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Metalized polyester film capacitors

Variable capacitors

3.2.3 Silicon Diode :

Silicon Diodes are electronic components that conduct current in only one direction. In function,

they are similar to one-way valves. Silicon Diodes are manufactured using semiconductor

materials such as silicon, germanium or selenium and are used as voltage regulators, signal

rectifiers, oscillators and signal modulators / demodulators.

Fig3.2.3 : Silicon Diode

Semiconductor diodes consist of a PN junction having two terminals, an anode (+) and a

cathode (-). Current flows from the anode to the cathode within the diode . Diodes can be used

as voltage regulators, tuning devices in RF tuned circuits, frequency multiplying devices in RF

circuits, mixers in RF circuits, switching applications, or can be used to make logic decisions in

digital circuits.

3.2.4 Resistors :

A resistor is a component of an electrical circuit that resists the flow of electrical current .A

resistor has two terminals across which electricity must pass, and is designed to drop the voltage

of the current as it flows from one terminal to the next. A resistor is primarily used to create and

maintain a known safe current within an electrical component.

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Resistor

Resistance is measured in ohms, after Ohm’s law. This rule states that electrical

resistance is equal to the drop in voltage across the terminals of the resistor divided by the

current being applied to the resistor .A high ohm rating indicates a high resistance to current.

This rating can be written in a number of different ways depending on the ohm rating.

Fig3.2.4: Resistor

The amount of resistance offered by a resistor is determined by its physical construction. A

resistor is coated with paint or enamel, or covered in molded plastic to protect it. Because

resistors are often too small to be written on, a standardized colour coding systems used to

identify them. The first three colors represent ohm value, and fourth indicate tolerance or how

close by percentage the resistor is to its ohm value. This is important for two reasons; the nature

of resistor construction is imprecise, and if used above its maximum.

Maximum power handling capacity of Resistors is

¼ Watt Max. 50mA

½ Watt Max. 70mA

1 Watt Max. 100mA

Watt Max. 140mA

20 Watt Max.440Ma

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3.2.5 LED (Light-emitting diode) :

A light-emitting diode (LED) is a semiconductor light source. LEDs are used as indicator lamps

in many devices and are increasingly used for other lighting. Appearing as practical electronic

components in 1962, early LEDs emitted low-intensity red light, but modern versions are

available across the visible, ultraviolet, and infrared wavelengths, with very high brightness.

Fig:3.2.5: LED(Light emitting diode)

When a light-emitting diode is forward-biased (switched on), electrons are able

to recombine with electron holes within the device, releasing energy in the form of photons. This

effect is called electroluminescence and the color of the light (corresponding to the energy of the

photon) is determined by the energy gap of the semiconductor. An LED is often small in area

(less than 1 mm2), and integrated optical components may be used to shape itsradiation

pattern. LEDs present many advantages over incandescent light sources including lower energy

consumption, longer lifetime, improved physical robustness, smaller size, and faster switching.

However, LEDs powerful enough for room lighting are relatively expensive and require more

precise current and heat management than compact fluorescent lamp sources of comparable

output.

Light-emitting diodes are used in applications as diverse as aviation

lighting, automotive lighting, advertising, general lighting, and traffic signals. LEDs have

allowed new text, video displays, and sensors to be developed, while their high switching rates

are also useful in advanced communications technology. Infrared LEDs are also used in

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the remote control units of many commercial products including televisions, DVD players and

other domestic appliances. LEDs are also used in seven-segment display.

3.2.6 Transistor :

A transistor is a semiconductor device used to amplify and switch electronic signals

and electrical power. It is composed of semiconductor material with at least three terminals for

connection to an external circuit. A voltage or current applied to one pair of the transistor's

terminals changes the current through another pair of terminals. Because the controlled

(output) power can be higher than the controlling (input) power, a transistor can amplify a signal.

Today, some transistors are packaged individually, but many more are found embedded

in integrated circuits.

Fig 3.2.6: Transistor

The transistor is the fundamental building block of modern electronic devices, and is

ubiquitous in modern electronic systems. Following its development in 1947 by John

Bardeen, Walter Brattain, and William Shockley, the transistor revolutionized the field of

electronics, and paved the way for smaller and cheaper radios,calculators, and computers, among

other things. The transistor is on the list of IEEE milestones in electronics, and the inventors

were jointly awarded the 1956Nobel Prize in Physics for their achievement.

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Chapter 4

Circuit Diagram and Explanation

4.1 Circuit Diagram:

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