Transcript FINAL_PROJECT2

‫بسم هللا الرحمن الرحيم‬
Project name :
Active Noise Reduction
Prepared by :
Ahlam Snouber & Safa’ Hashaiki
Supervisor: Dr Jamal Kharousheh
Abstract :
The main problem we improved it in our project is the
NOISE
First of all, noise has been known to cause stress.
Loud noises will give you headaches and make you
feel unwell. Constant noise can also give you
unhealthy stress that builds up over a long period of
time.
the idea behind this project is that by picking up
extraneous noise with a microphone on,
inverting that noise signal with a circuit, and
playing the inverted signal back through the
speakers, the two signals will add together to
zero and cancel the noise.
Background
Sound cancellation
If the sound waves were 180° or one-half a
wavelength out of phase, the sum of the
waveforms would be zero. They would cancel out
each other and there would be no sound.
Sum of waves equals zero sound
Not perfect
Since there are so many frequencies and fractions of
frequencies in some sounds, it is impossible to cancel
them all out with this method. Instead, the
electronics selects a narrow band of frequencies and
averages out the result. This is a fairly good job at
noise cancellation, but it is not 100%.
Introduction
Our project rely on the passive acoustic isolation of
speakers as well as ANR to provide broadband
noise reduction (figure A).
Figure A
ANR systems create anti-noise by first sampling the noise
with a microphone. In an open-loop systemAn inverting
amplifier outputs the anti-noise signal which is then mixed
with the desired signal so that when noise and anti-noise
meet, they cancel each other
Open loop systems have the advantage of simplicity, but
may not perform as well as other NC types.
Applications
There are a number of great applications for active noise
cancellation devices such as:
1. Honda cars
2. Headsets
3. Antenna satellite.
4.Air condition.
5. At studios .
6. At factories if it is developed
7. Although it can be used at home for example in refregenator or
fan of our computer as we made in our test .
The kind of integrated
circuit which we use
Description(
NE5532,OP275)
The NE5532 is a internally compensated dual low
noise
OP-AMP. The high small signal and power
bandwidth
provides superior performance in high quality AMP.
Pin Configuration Diagram for OP275
NE5532,OP275
LM358
Description
The LM358 consist of
two independent,
high gain, internally
Frequency
compensated operational
amplifiers which were
designed
specifically to operate
from a single power
supply over a
wide range of voltage
TBA810
description
The TBA810 is an
integrated circuit in
a 12-lead quad
in-line plastic
package,
intended for use as
a low frequency
class B amplifier.
The process
Before we started, we considered trying the
following experiments:
1.Sound canceling using analog devices
2. sound canceling using software
3.Noise cancellation specific to erasing ambient
noise and keeping directional noise
We decided to start with sound cancelling using an
analog circuit, and go on if we had time (which we
didn't).
We obtained:
.Hi-Fi op amps
.several resistors of varying
resistances
.electric-condenser microphones
.speaker
.bread board, wire, etc
.tba810 integrated circuit
.LM358 circuit
Experimentation
We started by building the circuit. As we went we
got a lot of circuits debugging experience! We
learned the truly inifinite benefits of the
multimeter ,oscilloscope ,measurements
,orcad,capture software to check our circuits and
designing it.
First circuit
the circuit of the microphone which is
used to pass the original signal is as follows :
How does it work
A microphone is connected to J1, a 1/8-inch stereo jack.
Electret-condenser microphones need a 2- to 10-volt bias
voltage for their internal FET pre-amps. That is
supplied by R2. A voltage-dividing network, which also
decouples the bias volt-age from the power supply That
division provided by Rl and Cl.
That is necessary due to the high gain of the entire
signal chain.
The first stage
How does it work??
The signals from the microphone go to
ICl-a.
an NE5532 set up as a standard non-inverting pre-amp.
The gain is set to one plus the ratio of R8/R6 in the feedback
path (1+R8/R6) . The total gain for that stage is about 31
dB.
A pair of high-pass filters is formed by C2/R4 and C4/R6.
Those filters block any DC that tries to slip through the preamp.
The second stage
How does it work??
From the output of the pre-amp, the microphone
signal is sent down two different paths. It feeds
both one pole of Sl-a and the phase-inverter. The
phase inverter is nothing more than a second
NE5532 configured as
a unity-gain inverting op-amp
(IC2-a).
The output of IC2-a is connected to the other pole of Sl-a.
That way,
Sl-a can select either the inverted or the non-inverted
signal.
The selected signal on Sl-a’s common pole goes to
potentiometer R14-a. That potentiometer sets the level of
the microphone signal feeding the speaker amplifier
The speaker circuit
The problem of this circuit
That type of op-amp configuration can be easily
modified to add a summing feature by the
inclusion of another load
So that we use another circuit to do the same
work with out that summing which is the
TBA810 CIRCUIT as follows
How does it work
this is Circuit is power amp 7W mono. Use IC TBA810 (
OLD IC).
Output to Speaker 4 OHM. Power Supply 12-14.4V
The circuit is provided with
a thermal limiting circuit which fundamentally changes
the criteria normally used in
determining the size of the heatsink So that after checking
this circuit we find that it is possible for working and
amplify the signal to the limited range
Until now we do the electrical part and we
achieve all the requirements which include
1.taking the sound through the microphone
2.amplifying it in the first stage
3.inverting that signal totally and with out
delay
4.amplifying the signal again to be suitable
for the speaker.
RESULTS
Result of first stage
Result of second stage
THE TRSULT OF THE SUMMER
CIRCUIT
Practical Result
Now we go to apply our project practically on a
fan of the computer which is considered as
asource of noise for along time.
How???
We put the microphone beside it
We return the speaker again from the other side
We turn on the fan
We open the switch of our project
The models use
We use two models
to sum the sounds
first model is
Y model as
follows:
2. the second model is I model as follows :
The sounds will mix together on the pole to
attenuate the source of the noise.
The results of our experience is good
The amplitude of noise is reduced as shown
here
The sound before the process
The sound after the process
FUTURE DEVELOPMENT
Active Noise Control( ANC)
The active noise cancellation system implements the
acoustically adaptive algorithm that cancels the
unwanted sound by generating an antisound (antinoise)
of equal amplitude and opposite phase. The original,
unwanted sound and the antinoise acoustically
combine, resulting in the .
The cancellation of both sounds
SYSTEM DESCRIPTION
The Development Kit contains the following basic
elements:
_ 2 Microphones
_ ANR Controller board
_ LCD Based user interface
_ 1 Speaker
_ CD
_ Power Supply
_ User manual
BENEFITS OF IT
Reduces noise of machinery fans and blowers up to 20dBA
_ Easily programmable user interface, 2 button operation and
LCD display.
_ Adaptable for both point to point and point to zone ANC
applications
_ Real time adaptive algorithms
_ Self calibrated system
_ Computer connection not necessary
_ Ideal for acoustic and vibration applications
The problems which face us
through working
1.determining the kind of amplifier suitable for low noise or low
frequency (not any amplifier is suitable)
Then finding the integrated circuit itself contained the amplify
which is NE5532
2. calculation of the value of the gain for each stage calculated by
the value of the resistor amounted the amplifier which we solve it by
using orcad and capture programme software .
3. after the successful of our circuit electrically and by using
summary circuit ,when we want to apply it practically we don’t
find the suitable form
We cant apply to any device because it is for only low noise with
long time.
4.difficult to find suitable place for microphone and speaker.
5. also the place where the noise can be cancelled or where is the
point of cancellation
So we use two model to add the two signals together to give us small
summation
The first model is Y form
And the other is I form
The most difficult problem
7.the difficult to protect the result in save because
our work is online and in any moment may have
any error despite small error make the result
different .
The End
We are ready for any inquiry