08-07-2014, 11:50 AM
Electronic Noise meter
[attachment=65728]
INTRODUCTION
Unwanted 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, increased Cortsol 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.
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 i.e., 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 kPa Sound 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.
NOISE DETECTOR
This circuit is intended to signal, through a flashing LED, the exceeding of a fixed threshold in room noise, chosen from three fixed levels, namely 50, 70 & 85 dB. Two Op-amps provide the necessary circuit gain for sounds picked-up by a miniature electrets microphone to drive a LED. With SW1 in the first position the circuit is off. Second, third and fourth positions power the circuit and set the input sensitivity threshold to 85, 70 & 50 dB respectively. Current drawing is <1mA with LED off and 12-15mA when the LED is steady on.
SPEAKER PROTECTOR CIRCUIT
When the amplifier is switched on, the speaker gets popped up by a high voltage and a loud thud sound can be heard from the speaker. This is very harmful to the speaker and it drastically reduces the speaker’s life. The speaker protector circuit connects the speaker to the power amplifier output only after a few seconds the amplifier is powered ON.
A simple transistor based time delay circuit is used for attaining the purpose. The circuit is so connected to the existing amplifier that, when the amplifier is powered on the bridge also gets powered through the amplifier’s power switch.
BLOCK DIAGRAM
When it is important to measure noise accurately a meter is required. The meter consists of an amplifier, a rectifier, an averager and a DC meter.
Very important in respect to complexity and cost of the equipment is the required accuracy of the noise measurement. As in other measurement tasks one should avert from using more accuracy than appropriate to the design problem under consideration
CIRCUIT DESCRIPTION
The Noise meter is designed to measure the sound level in the room in terms of decibel. The circuit has three sections – A sound detector, Inverting amplifier and an analogue display driver. The input section has a sound detector comprising a condenser Micro phone and associated components like R1, C4 and R2. Resistor R1 regulates the current flowing into the mic, and determines its gain Capacitor C4 is the DC blocking capacitor to remove DC fraction from the sound signals generated by the mic. Resistor R4 (12K) along with feedback resistor R5 (10M) determines the gain of the amplifier built around IC 1.
WORKING OF THE CIRCUIT
The circuit comprises a sound intensity sensor and a display unit.
The sound intensity sensor is built around a condenser microphone. Op amp IC CA 3130 (IC2) and associated components Op amp IC2 is configured as a high gain inverting amplifier. The voltage supply to IC2 at its non inverting Pin 3 is divided to half by resistors R3 and R4, which is also used as the reference voltage. Resistor R1 determines the sensitivity of the condenser microphone.
The microphone picks up sound vibrations and converts them into the corresponding electric pulses, which are fed to the inverting input of IC 2 (Pin 2) via capacitor C4 and resistor R2 Capacitor C4 blocks any DC entering the op-amp, since it may affect the functioning of the op-amp. The output of IC 2 is connected to the inverting input through resistor R5 (10 M) for negative feedback. Since the input impedance of IC2 is very high even a small current can activate the op-amp.
The output of IC2 is given to preset VR1 via capacitor C5, which is used to control the volume. Capacitor C5 blocks DC, allowing only AC to pass through preset VR 1. The AC signals from the wiper of VR 1 are fed to a diode pump comprising diodes D1 & D2. The diode pump rectifies the AC and maintains it at the output level of IC2. Capacitor C6 acts as a reservoir capacitor for DC and resistor R6 provides the path for its discharge
Diodes
The diode is fabricated of a semiconductor material, usually silicon, which is doped with two impurities. One side is doped with a donor or n-type impurity which releases electrons into the semiconductor lattice. These electrons are not bound and are free to move about. Because there is no net charge in the donor impurity, the n-type semiconductor is electrically neutral. The other side is doped with an acceptor or p-type impurity which imparts free holes into the lattice. A hole is the absence of an electron which acts as a positive charge. The p-type semiconductor is also electrically neutral because the acceptor material adds no net charge
Op Amp
The OpAmp was originally designed to carry out mathematical operations in analogue computers, such as bombsights, but was soon recognized as having many other applications. The OpAmp usually comes in the form of an 8 pin integrated circuit, the most common one being the type 741. It has two inputs and one output. The input marked with a - sign produces an amplified inverted output. The input marked with a + sign produces an amplified but non inverted output. The OpAmp requires positive and negative power supplies, together with a common ground. Some circuits can be designed to work from a single supply. If the two inputs are joined together, then the output voltage should be midway between the two supply rails, i.e. zero volts.
If it is not, then there are two connections for adding a potentiometer, to remove this OFFSET. The OpAmp has a very high gain, typically (100 dB) 100,000 times. Looking at the left hand diagram, an input with a swing of a fraction of milli volts produces an output that changes between + 12 volts and - 12 volts. In most cases
PCB DESIGN AND FABRICATION
PCB FABRICATION
The PCB manufacturing process involves use of expensive equipments, but homebrew PCB fabrication is less expensive .It requires Intel Pentium PC,600-1200dpi laser printer with premium-quality paper or butter-paper and miscellaneous items like single side copper laminated board, Lacquer thinner, sand paper and others. The various steps involves in PCB fabrication are:
1. PC-based artwork
2. Printing on a laser jet printer
3. Transfer of pattern to copper plate using cloth iron
4. Etching and Drying
5. Drilling and cleaning
6. Caution
SOLDERING
Soldering is the process of joining metals by using lower melting point metal to wet or alloy with the joined surfaces. Solder is the joining material. It melts below 427’C. Soldered joints in electronic circuits will establish strong electrical connections between component leads. The popularly used solders are alloys of tin and lead that melt below the melting point of tin. In order to make the surfaces accept the solder readily, the component terminals should be cleaned chemically or by abrasion using blades or knives. Small amount of lead coating can be done on the cleaned portion of the leads using soldering iron. This process is called tinning. Zinc chloride or ammonium chloride separately or in combination are the most commonly used fluxes. These are available in petroleum jelly as paste flux. A solder joint can at
RESULT ANALYSIS & DISCUSSION
By the completion of this project we have acquired the knowledge of Noise meter features and the project as the noise measurement device with the amorous feature of the circuit. The Noise meter on test performed exceptionally well to its capability and accuracy. All the inherent parts of the circuit performed consistently. It helped us to come out with good judgment. With the features what it inherits, it seems to be advantageous to the present era. This project was the real challenge for us to implement. Lot of problem has come but under the perfect guidance and facilities we challenge those problems and at last we have completed our project in well manner.
FUTURE PROSPECTS AND APPLICATIONS
This project can be applied in the places where we have to keep a check on the noise level that is, when it is desired that the noise level should not exceed pre determined level. Some of the possible applications are:
• Noise meters are used to test work environments, ensuring that noise regulations are observed.
• Used in urban planning to evaluate traffic noise, as well as noise from aircraft, trains and other transportation systems.
• Used to investigate noise complaints from construction, music and traffic.
• It can be used in school and college libraries.
• It can also be used in hospitals and laboratories.
This project can be modified by connecting to Audio announcement circuit. So our project continuously measure sound pressure, and compare with critical noise level set using microcontroller programming. If sound noise pressure exceed from set value, voice announcement circuit start play, giving warning massage. Thus this modified project measures sound pressure level and display it on 16*2 LCD. This project can be very useful for the college library and everywhere where noise level matter.
CONCLUSION
This ‘Electronic Noise meter’ is made from the basic components like. Transistors, resistors, capacitors, diodes IC chips etc is meant to display the noise level in a room. The basic advantage of this Noise meter is that it works in a 9-V battery and hence would work even at the time of power failure. This device can be placed at hospitals, libraries, laboratories, Silent Zones etc to monitor the sound levels.
[attachment=65728]
INTRODUCTION
Unwanted 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, increased Cortsol 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.
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 i.e., 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 kPa Sound 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.
NOISE DETECTOR
This circuit is intended to signal, through a flashing LED, the exceeding of a fixed threshold in room noise, chosen from three fixed levels, namely 50, 70 & 85 dB. Two Op-amps provide the necessary circuit gain for sounds picked-up by a miniature electrets microphone to drive a LED. With SW1 in the first position the circuit is off. Second, third and fourth positions power the circuit and set the input sensitivity threshold to 85, 70 & 50 dB respectively. Current drawing is <1mA with LED off and 12-15mA when the LED is steady on.
SPEAKER PROTECTOR CIRCUIT
When the amplifier is switched on, the speaker gets popped up by a high voltage and a loud thud sound can be heard from the speaker. This is very harmful to the speaker and it drastically reduces the speaker’s life. The speaker protector circuit connects the speaker to the power amplifier output only after a few seconds the amplifier is powered ON.
A simple transistor based time delay circuit is used for attaining the purpose. The circuit is so connected to the existing amplifier that, when the amplifier is powered on the bridge also gets powered through the amplifier’s power switch.
BLOCK DIAGRAM
When it is important to measure noise accurately a meter is required. The meter consists of an amplifier, a rectifier, an averager and a DC meter.
Very important in respect to complexity and cost of the equipment is the required accuracy of the noise measurement. As in other measurement tasks one should avert from using more accuracy than appropriate to the design problem under consideration
CIRCUIT DESCRIPTION
The Noise meter is designed to measure the sound level in the room in terms of decibel. The circuit has three sections – A sound detector, Inverting amplifier and an analogue display driver. The input section has a sound detector comprising a condenser Micro phone and associated components like R1, C4 and R2. Resistor R1 regulates the current flowing into the mic, and determines its gain Capacitor C4 is the DC blocking capacitor to remove DC fraction from the sound signals generated by the mic. Resistor R4 (12K) along with feedback resistor R5 (10M) determines the gain of the amplifier built around IC 1.
WORKING OF THE CIRCUIT
The circuit comprises a sound intensity sensor and a display unit.
The sound intensity sensor is built around a condenser microphone. Op amp IC CA 3130 (IC2) and associated components Op amp IC2 is configured as a high gain inverting amplifier. The voltage supply to IC2 at its non inverting Pin 3 is divided to half by resistors R3 and R4, which is also used as the reference voltage. Resistor R1 determines the sensitivity of the condenser microphone.
The microphone picks up sound vibrations and converts them into the corresponding electric pulses, which are fed to the inverting input of IC 2 (Pin 2) via capacitor C4 and resistor R2 Capacitor C4 blocks any DC entering the op-amp, since it may affect the functioning of the op-amp. The output of IC 2 is connected to the inverting input through resistor R5 (10 M) for negative feedback. Since the input impedance of IC2 is very high even a small current can activate the op-amp.
The output of IC2 is given to preset VR1 via capacitor C5, which is used to control the volume. Capacitor C5 blocks DC, allowing only AC to pass through preset VR 1. The AC signals from the wiper of VR 1 are fed to a diode pump comprising diodes D1 & D2. The diode pump rectifies the AC and maintains it at the output level of IC2. Capacitor C6 acts as a reservoir capacitor for DC and resistor R6 provides the path for its discharge
Diodes
The diode is fabricated of a semiconductor material, usually silicon, which is doped with two impurities. One side is doped with a donor or n-type impurity which releases electrons into the semiconductor lattice. These electrons are not bound and are free to move about. Because there is no net charge in the donor impurity, the n-type semiconductor is electrically neutral. The other side is doped with an acceptor or p-type impurity which imparts free holes into the lattice. A hole is the absence of an electron which acts as a positive charge. The p-type semiconductor is also electrically neutral because the acceptor material adds no net charge
Op Amp
The OpAmp was originally designed to carry out mathematical operations in analogue computers, such as bombsights, but was soon recognized as having many other applications. The OpAmp usually comes in the form of an 8 pin integrated circuit, the most common one being the type 741. It has two inputs and one output. The input marked with a - sign produces an amplified inverted output. The input marked with a + sign produces an amplified but non inverted output. The OpAmp requires positive and negative power supplies, together with a common ground. Some circuits can be designed to work from a single supply. If the two inputs are joined together, then the output voltage should be midway between the two supply rails, i.e. zero volts.
If it is not, then there are two connections for adding a potentiometer, to remove this OFFSET. The OpAmp has a very high gain, typically (100 dB) 100,000 times. Looking at the left hand diagram, an input with a swing of a fraction of milli volts produces an output that changes between + 12 volts and - 12 volts. In most cases
PCB DESIGN AND FABRICATION
PCB FABRICATION
The PCB manufacturing process involves use of expensive equipments, but homebrew PCB fabrication is less expensive .It requires Intel Pentium PC,600-1200dpi laser printer with premium-quality paper or butter-paper and miscellaneous items like single side copper laminated board, Lacquer thinner, sand paper and others. The various steps involves in PCB fabrication are:
1. PC-based artwork
2. Printing on a laser jet printer
3. Transfer of pattern to copper plate using cloth iron
4. Etching and Drying
5. Drilling and cleaning
6. Caution
SOLDERING
Soldering is the process of joining metals by using lower melting point metal to wet or alloy with the joined surfaces. Solder is the joining material. It melts below 427’C. Soldered joints in electronic circuits will establish strong electrical connections between component leads. The popularly used solders are alloys of tin and lead that melt below the melting point of tin. In order to make the surfaces accept the solder readily, the component terminals should be cleaned chemically or by abrasion using blades or knives. Small amount of lead coating can be done on the cleaned portion of the leads using soldering iron. This process is called tinning. Zinc chloride or ammonium chloride separately or in combination are the most commonly used fluxes. These are available in petroleum jelly as paste flux. A solder joint can at
RESULT ANALYSIS & DISCUSSION
By the completion of this project we have acquired the knowledge of Noise meter features and the project as the noise measurement device with the amorous feature of the circuit. The Noise meter on test performed exceptionally well to its capability and accuracy. All the inherent parts of the circuit performed consistently. It helped us to come out with good judgment. With the features what it inherits, it seems to be advantageous to the present era. This project was the real challenge for us to implement. Lot of problem has come but under the perfect guidance and facilities we challenge those problems and at last we have completed our project in well manner.
FUTURE PROSPECTS AND APPLICATIONS
This project can be applied in the places where we have to keep a check on the noise level that is, when it is desired that the noise level should not exceed pre determined level. Some of the possible applications are:
• Noise meters are used to test work environments, ensuring that noise regulations are observed.
• Used in urban planning to evaluate traffic noise, as well as noise from aircraft, trains and other transportation systems.
• Used to investigate noise complaints from construction, music and traffic.
• It can be used in school and college libraries.
• It can also be used in hospitals and laboratories.
This project can be modified by connecting to Audio announcement circuit. So our project continuously measure sound pressure, and compare with critical noise level set using microcontroller programming. If sound noise pressure exceed from set value, voice announcement circuit start play, giving warning massage. Thus this modified project measures sound pressure level and display it on 16*2 LCD. This project can be very useful for the college library and everywhere where noise level matter.
CONCLUSION
This ‘Electronic Noise meter’ is made from the basic components like. Transistors, resistors, capacitors, diodes IC chips etc is meant to display the noise level in a room. The basic advantage of this Noise meter is that it works in a 9-V battery and hence would work even at the time of power failure. This device can be placed at hospitals, libraries, laboratories, Silent Zones etc to monitor the sound levels.