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CHAPTER 1
INTRODUCTION
Sound is an important part of human life. Sound has some good and bad effect on our life.
Because of sound we can communicate with each other, we can enjoy beautiful music and so on.
But some time sound irritates us. Loud sound generally called as noise causes many health
problem like headache, decrease in hearing capacity etc. a sonic bomb can shatter a window and
shake plaster of walls. Sound plays an important role in engineering and medical field. From
following figure you will get a rough idea of scope of acoustic.
Figure 1.1 Scopes of Acoustics[12]
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Sound is used for such a wide purpose. So it is essential to measure sound waves in term of
frequency or db level. Measurements provide definite quantities which describe and rate sounds.
These measurements can provide benefits such as improved building acoustics and loudspeakers,
thus increasing our enjoyment of music, both in the concert hall and at home. Sound
measurements also permit precise, scientific analysis of sounds. In past few years various
instruments for measuring sound waves are developed. These instruments are discussed in this
report.
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CHAPTER 2
BASIC OF SOUND
A sound wave is an air pressure disturbance that results from vibration. The vibration can come
from a tuning fork, a guitar string, the column of air in an organ pipe, the head (or rim) of a snare
drum, steam escaping from a radiator, the reed on a clarinet, the diaphragm of a loudspeaker, the
vocal cords, or virtually anything that vibrates in a frequency range that is audible to a listener
(roughly 20 to 20,000 cycles per second for humans). The two conditions that are required for
the generation of a sound wave are a vibratory disturbance and an elastic medium.
2.1 Propagation of sound
Figure 2.1 Propagation of Sound[21]
When sound produce air pressure varies in atmosphere. It forms alternate compression and
rarefaction. In compression pressure is greater than atmospheric pressure that in rarefaction
lower than atmospheric pressure. For better understanding one can imagine ripples in pond
caused by stone throne in water. Sound pressure fluctuates up and down like waves therefore it is
called as sound waves.
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2.2 Characteristics of Sound Waves
Amplitude:
At any point on the wave, the vertical distance of the wave from the centerline is called the
amplitude of the wave. As amplitude increases loudness of sound also increases.
Frequency:
The number of cycles completed in one second is called the frequency.
Wavelength:
When a sound wave travels through the air, the physical distance from one peak (compression) to
the next is called a wavelength. Higher the frequency lowers the wavelength and vice versa.
Figure 2.2 Examples of Higher Frequency and Lower Frequency[11]
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Phase and Phase Shift:
The phase of any point on the wave is its degree of progression in the cycle - the beginning, the
peak, the trough, or anywhere in between. If there are two identical waves, butone is delayed
with respect to the other, there is a phase shift between the two waves. The more delay, the more
phase shift. Phase shift is measured in degrees.
Figure2.3 Example of Phase Shift[15]
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Harmonic Content:
In figure three frequencies are combined to form complex waves. The amplitude of the various
waves are added algebrically at the same point in time to obtained final complex waveform. The
lowest frequency in complex waves is called the fundamental frequency. It determine the pitch
of sound. Higher frequencies in the complex wave are called overtones or upper partials. If the
overtones areintegral multiples of the fundamental frequency, they are called harmonics.For
example, if the fundamental frequency is 200 Hz, the second harmonic is 400 Hz (2 x 200); the
third harmonic is 600 Hz (3 x 200), and so on.
Figure 2.4 Complex Waveform[15]
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CHAPTER 3
DIFFERENT TYPES OF TRANSDUCER
3.1 Microphone
Microphones are transducer which converts acoustical energy into electrical energy. Microphone
is interface between acoustic field and measuring system. It converts sound pressure in to
electrical signals which then can be interpreted by the measuring system. Microphones are
mainly classified in two major groups one who are sensitive to sound pressure and other
sensitive to velocity of particle. There are several types of microphone construction dynamic and
capacitor type of microphones is widely used. There is no such concept of perfect microphone
exist as every microphone has its own strength and weaknesses. Choosing appropriate
microphone makes the job easy. There are many type of microphone such as ribbon microphone,
liquid microphone, laser microphone, fiber optic microphone. Some of the microphones are
discussed in this chapter.
3.1.1 Dynamic Microphone or Moving Coil Microphone
It is the simplest microphone. The signal is created when a coil of wire attached to a diaphragm
moves in and out, through a magnetic field, as the air pressure changes. An electrical signal is
created by induction as the wires in the coil cut through the magnetic field. . Dynamic
microphones tend to be quite sturdy and of low cost, so they are commonly used to record
drums, amplifier outputs, human voices, and other sources which produce high sound pressure
levels. A resonant peak is usually found at around 5 kHz, making it a favorite with vocalists.
Figure 3.1 Dynamic Microphones[20]
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3.1.2 Ribbon Microphone
Ribbon type microphone is the part of dynamic microphone. It consists of a thin strip of
conductive corrugated metal (ribbon) between magnetic plates. Vibration of the ribbon according
to the acoustic wave induces a current. The lightness of the ribbon guarantees a flat frequency
response for mid and high frequencies up to 14 kHz. It resonates at very low frequencies (around
40Hz). It is very delicate and well suited for the recording of acoustic instruments. They are,
however, considerably more fragile than moving coil types.
Figure 3.2 Ribbon Microphone[19]
3.1.3 Condenser Microphone
A capacitor is an electrical device able to store electrical charge between two closely-spaced
conductors. In a condenser microphone, the microphone membrane is built parallel to a fixed
plate and forms with it a condenser. A potential differential is applied between the two platesusing a d.c. voltage supply (the polarisation voltage). The movements, which the sound waves
provoke in the membrane, give origin to variations in the electrical capacitance and therefore in a
small electric current. These microphones are more accurate than the other types and are mostly
used in precision sound level meters.r, they are more prone to being affected by dirt and
moisture.
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Figure 3.3 Condenser Microphone[19]
3.1.4 Carbon Microphone
The principle of operation was both simple and ingenious. Sound waves strike the diaphragm
and move it. The movement of diaphragm causes a plunger or piston to move with it. The
plunger compresses and decompresses a chamber filled with carbon granular. Now, carbon
granular will conduct electric current. If a battery is connected to the microphone terminals a
current will flow. How much current will flow will depend on the degree of compression of
carbon granular. Carbon microphones are no longer in use as they give poor quality.
Figure 3.4Carbon Microphones[4]
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3.1.5 Crystal Microphone
Sound waves striking the diaphragm cause varying pressure to be applied to the crystal, which in
turn causes the microphone to produce an output voltage in sympathy with the sound waves. A
crystal microphone does not required battery. Like the dynamic microphone, it directly converts
mechanical energy in to electrical energy.
Figure 3.5 Crystal Microphone[4]
3.2 Characteristics of Microphone
3.2.1 Sensitivity of Microphone
The sensitivity of a microphone is defined as the amplitude (in mV) of the output signal for an
incident sound pressure of amplitude 1 Pa (94 dB) at 1000 Hz. It can also be expressed in
decibels by the following expression:
Sensitivity = 20log10 Vp0/V0p dB re 1V/Pa (1)
Thus, a microphone giving an output signal V of 10 mV for a pressure signal p of 94 dB has a
sensitivity of 10 mV/Pa or -40 dB. Here p0 = 1Pa and V0 = 1 volt.
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3.2.2 Frequency response
The frequency response characteristic is usually flat for good quality piezoelectric or condenser
microphones from 2 Hz to an upper limit which depends on their size. This limit is about 2 kHz
for a 1" diameter microphone, 4 kHz for a 1/2" and 8 kHz for a 1/4" microphone. Below this
limit, the frequency response is independent of the orientation of the microphone with respect to
the noise source, and therefore the microphone can be held in any orientation. Above this limit,
the frequency response will depend upon the direction of the sound wave on the microphone
membrane.
Figure 3.6 Frequency response of a free field (0) microphone[2]
Some microphones have been designed in order for the response characteristics to be flat when
the sound direction of propagation is perpendicular to the membrane. These microphones are
called free field microphones and should be oriented toward the most significant sound source.
In above figure we can see frequency response is almost flat for 00
but when sound waves
incident equally from all possible direction it is not flat. (Response is shown by R curve in
figure)
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Figure 3.7 Frequency response of a diffuse field (R) microphone[2]
Other microphones have been designed for the response characteristics to be flat when the sound
comes in all directions at the same time as in a diffuse field. They are called diffuse field
microphones. Their frequency response characteristic is very near the response characteristic
under an incidence of 70 and these microphones should therefore be oriented at 70 toward the
predominant sound source. In figure we can see straight response curve R which is at 70
0
.
3.2.3 Dynamic Range
The output of a microphone is limited on the one hand by the internal noise of the transducer and
on the other hand by the distortion resulting from high noise levels. In addition, the instrument to
which the output signal of the microphone is fed will saturate if the signal is too high and will
also give a false result (that is, its background noise level) if the signal is too low. Therefore,
high sensitivity microphones are needed to measure very low noise levels (lower than 30 dB),
and low sensitivity ones have to be used for high noise levels such as for impact noise (above
130 dB). The dynamic range of typical good quality microphones is thus between 100 and 120
dB.
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CHAPTER 4
DIFFERENT WAYS OF SOUND MEASUREMENT
Many types of measuring systems can be used for the measurement of sound depending on the
purpose of the study, the characteristics of sound and the extent of information that is desired
about the sound. Various instrument used for the measuring of sound is as follows:
SOUND LEVEL METERS
FREQUENCY ANALYZERS
NOISE DOSIMETERS
RECORDERS
Many types of measuring systems can be used for the measurement of sound depending on the
purpose of the study, the characteristics of sound and the extent of information that is desired
about the sound. The various elements in a measuring system are:
The transducer; that is, the microphone
The electronic amplifier and calibrated attenuator for gain control
The frequency weighting or analyzing possibilities
The data storage facilities
The display
It is not necessary that the entire above element will be used in every measuring device but
microphone is very important device and used in almost all the sound measuring device.
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4.1 Sound Level Meter (SLM)
The electrical signal from the transducer is fed to the pre-amplifier of the sound level meter and
if needed, a weighted filter over a specified range of frequencies. Further amplification prepares
the signal either for output to other instrument such as a tape recorder or for rectification and
direct reading on the meter. The rectifier gives the RMS value of the signal. The RMS signal is
then exponentially averaged using a time constant of 0.1 s ("FAST") or 1 s ("SLOW") and the
result is displayed digitally or on an analog meter.
Figure 4.1 Sound level meter block diagram[2]
According to measurement precision there are four types of sound level meters i.e.0, 1, 2 and 3.
The type 0 sound level meters is intended as laboratory reference standard. Type 1 is intended
especially for laboratory use and for field use where the acoustical environment has to be closely
specified and controlled. The type 2 sound level meter is suitable for general field application.
The type 3 is intended primarily for field noise survey application. The frequency response for
all types is defined from 10 Hz to 20000 Hz with a higher accuracy at frequencies from 100Hz to
8000Hz.
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4.2 Frequency Analyzer
The objective of frequency analysis is to determine how the overall level is distributed over a
range of frequencies. The most usual analysis for occupational hygiene noise studies is octave
band analysis. For more detailed information, narrower bands can be used such as one-third
octave analysis or constant bandwidth analysis.
There are two basic forms of spectrum analyzers, swept tuned and real-time. As the description
suggests, a swept tuned analyzer is tuned by electronically sweeping its input over the desired
frequency range thus, the frequency components of a signal are sampled sequentially in time.
Using a swept tuned system enables periodic and random signals to be displayed but does not
allow for transient responses.
Real time analyzers however, sample the total frequency range simultaneously, thus preserving
the time dependency between signals. This technique allows transient and periodic / random
signals to be displayed.
A number of analyzers are available for use with the sound level meter. The simplest models are
sets of passive filters (octave or one third octave) that can be inserted between the two amplifiers
of the SLM. Other analyzers are specific instruments making it possible to automatically scan the
whole range of frequency bands. These are sequential instruments making measurements in one
band at a time. This strongly restricts their use as the noise must be constant both in amplitude
and in frequency during the 5 to 10 minutes of the analysis.
More sophisticated analyzers have the possibility to make the frequency analysis in all desired
bands at the same time. These are analyzers using a set of parallel filters or using the fast Fourier
transform of the input signal before recombining the data into the desired bands.
One important aspect to be considered about the filters is their frequency characteristics. Ideally,
the filter should provide an attenuation of infinity outside the band. In practice, this is never the
case. For most common filters, the attenuation at the cut off frequencies is usually around 3 dB
and is some 24 dB per doubling of frequency outside that range. Figure gives the typical
frequency characteristic of an octave band filter. The practical implication of this is that a signal
of 100 dB at 1000 Hz for instance will give a reading of 76 dB in the octave bands centered at
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500 Hz and 2000 Hz, although no energy is present at frequencies covered by these two octave
bands.
Figure 4.2 Typical 500Hz Octave Band Filter Characteristic[2]
Figure 4.3 Example of the Octave Spectrum of a Noise Including a Pure Tone in the Octave
Centered At 1000 Hz[2]
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As an example, consider the octave band spectrum of figure 6.5, presenting a predominant value
for the 1000 Hz octave band (106 dB). A pure tone of 106 dB at 1000 Hz would give a reading
of 106 - 24 = 82 dB both for the 500 Hz and the 2000 Hz octave bands. The levels of 90 and 91
dB respectively would not be very much influenced by this and therefore would reflect the total
intensity at frequencies inside these bands.
However the frequency of the pure tone might be 1175 Hz: the attenuation provided by the 2000
Hz octave band filter would then be 15 dB and the level in this band 91 dB. Similarly for a 860
Hz tone, the attenuation for the 500 Hz octave band would be 16 dB and the level wrongly
estimated at 90 dB.
Advantage of Frequency Analyzer
The advantage of this technique is its speed. Because FFT spectrum analyzers measure all
frequency components at the same time, the technique offers the possibility of being hundreds of
times faster than traditional analog spectrum analyzers. In the case of a 100 kHz span and 400
resolvable frequency bins, the entire spectrum takes only 4 ms to measure. To measure the signal
with higher resolution, the time record is increased. But again, all frequencies are examined
simultaneously providing an enormous speed advantage.
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4.3 Noise Dosimeter or Personal Noise Exposure Meter (PSEM)
Noise dose is not mentioned in the noise regulation, but it is useful to understand this important
concept as many noise calculations use noise dose. Also, noise dosimeters are frequently used in
occupational noise survey work. Noise dosimeter is also known as Personal noise dosimeter or
Personal noise exposure meter.
A noise dose is a way of quantifying an amount of noise to which a worker is exposed. A noise
dose can be expressed:
As a percentage of an acceptable, or criterion noise dose, or
In terms of absolute units, known as Pa2h (say Pascal squared hours)
A worker exposed to the daily limit of LEX = 85 dBA (over 8 hours/day) receives the criterion
dose of 100% (" 1 Pa2h).
Noise dosimeters are noise integrating devices small enough to be worn by workers. They are
used for personal noise sampling over long periods of time. At the end of the sampling time, they
indicate the noise exposure dose acquired during that time. It is worth noting that the
characteristics of the dosimeters have never been standardized. Furthermore, they are extremely
limited as they provide one single value at the end.
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Advantage and disadvantage of SLM and PSLM
When using SLMs, small inaccuracies in measured levels or estimated exposure time can have
significant effects on the resulting daily noise exposure level, particularly when noise levels are
high. They are however useful for gathering large amounts of information quickly and in the
hands of a skilled noise assessor, the results are usually reliable.
While PSEMs obviate the need for these various approximation and estimates, they do have their
own inherent inaccuracies due to the manner in which they are used in practice, they are used in
practice. They do however provide a longer term monitoring option for which a SLM would be
impractical. A PSEM can provide information which would otherwise be missed using only a
SLM, and is the more useful tool for assessing noise climate change over time. Again an
experienced noise assessor can examine and interpret the results with a good degree of
confidence.
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4.4 RECORDER
4.4.1 Graphic level recorder
If the sound level meter has a logarithmic DC output facility, common graphic recorders can be
used to obtain a permanent record of the evolution of the sound level, providing that their writing
speed is compatible with the SLOW or FAST characteristics of the SLM. If there is no DC
output or if this output is not proportional to the dB level but only to the RMS pressure, then a
special recorder must be used.
Characteristic of graphic level recorder
the RMS detection capabilities
the frequency response
The writing speeds, that should at least correspond to the slow and fast characteristics of
the sound level meter. For reverberation time measurements, however, much faster
writing speeds are needed the dynamic range of the graph (often 25 or 50 dB) and of the
instrument. It is usually not practical to record graphically the instantaneous noise level at
a workplace for extended periods of time: the graph allows only the determination of
maximum and minimum levels and cannot be used to define any average level. The use
of this technique should be restricted to special cases such as:
the characterization of short event of noise
the determination of intermittency of noise
the study of reverberation of time recording of frequency analysis
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4.4.2 Magnetic Tape Recorders
Magnetic tape recorders are used to make a permanent recording of the noise for future analysis
or reference. Some HIFI audio recorders can be used, providing their frequency response and
dynamic range are suitable. For general surveys, small recorders with a frequency response of +
3 dB in the range 30 Hz to 16 kHz and a dynamic range of 40 dB may be sufficient. For precise
measurements and frequency analyses, higher quality instrumentation is needed. The real
objectives of the instrument have to be assessed since the relative price of these instruments may
vary in the range of 1 to 20.
As the dynamic range of an analog recorder is no more than 40 to 50 dB, usually it is difficult or
impossible to record impulse noise as met in industry or as used for measuring the reverberation
time. Some digital recorders (referred to as DAC recorders) are now available: they have a much
broader dynamic range (around 90 dB) and a good frequency response (2018000 Hz).
Besides analog and digital recorders, there are also frequency modulated (FM) recorders which
are of special interest for measuring vibration as their frequency range extends down to DC. The
criteria for the selection of a tape recorder are:
The frequency responds at the different speeds. Usually the limits are directly proportional to the
speed
The range of speeds
The dynamic range
The cross channel attenuation
The presence of band pass filters enabling the elimination of low frequency noise
The quality of the indicating device and of the input potentiometers, preferably graduated
in dB
The possibility of controlling the output signal
The protection against dust
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Advantage of Magnetic Tape Recorder
Capacity
One of the key advantages of magnetic tape is its capacity for holding data. Magnetic tape was
the first medium able to hold a feature-length movie on a small, inexpensive device, thus
enabling the home video market of the 1980s. In addition, compact cassettes can hold music on
both sides, giving them a 90-minute total playing time, which is even greater than most CDs.
Editing
Magnetic tape is also easy to edit using a traditional linear-editing system. This can involve
duplicating a portion of a tape to a master reel, or physically cutting the tape and attaching the
desired portions together with glue, splicing cement or adhesive tape. Editing in this manner
requires no special computer equipment and may be less expensive and/or easier to learn than
nonlinear digital editing.
Disadvantage of Magnetic Tape Recorder
Generation Loss
One of the disadvantages of magnetic tape is generation loss, which refers to the fact that each
successive copy of a tape loses quality compared to the original. This can make it difficult to use
magnetic tape for editing-intensive projects, or when extremely high fidelity is important. Digital
media, on the other hand, can be copied and reproduced indefinitely with no visible or audible
difference between the original and any of its copies.
Durability
Another problem with magnetic tape is its tendency to stretch out over time, causing the quality
of the data to deteriorate. On old video tapes, this generally appears in the form of poor audio,
and picture data can eventually suffer as well. Over time magnetic tape acquires a layer of
magnetic debris from recording and playback heads, which may need to be cleaned periodically
to continue functioning.
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CHAPTER 5
Data Acquisition System
The purpose of data acquisition is to measure an electrical or physical phenomenon such as
voltage, current, temperature, pressure, or sound. PC-based data acquisition uses a combination
of modular hardware, application software, and a computer to take measurements. While each
data acquisition system is defined by its application requirements, every system shares a
common goal of acquiring, analyzing, and presenting. Data acquisition systems incorporate
signals, sensors, actuators, signal conditioning, data acquisition devices, and application
software.
Figure 4.4 PC based Data Acquisition[12]
5.1 DAQ used for Sound Measurement
The hardware that used is generally provided by NATIONAL INSTRUMENT (NI).
A) NI cDAQ-9172
The NI cDAQ-9172 is an eight-slot NI Compact DAQ chassis that can hold up to eight CSeries I/O modules. The chassis operates on 11 to 30 VDC and includes an AC/DC
power converter. The NI cDAQ-9172 is a USB 2.0-compliant device that includes a 1.8
m USB cable.
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Sound And Its Different Ways Of Measurement
Figure 4.5 NI cDAQ 9172[16]
The NI cDAQ-9172 has two 32-bit counter/timer chips built into the chassis. With a
correlated digital I/O module installed in slot 5 or 6 of the chassis, you can access all thefunctionality of the counter/timer chip including event counting, pulse-wave generation
or measurement, and quadrature encoders.
B) NI WLS-9234, NI 9233, NI 9234
The NI WLS-9234 is a four-channel IEEE 802.11 wireless or Ethernet C Series dynamic
signal acquisition module for making high-accuracy audio frequency measurements from
integrated electronic piezoelectric (IEPE) and non-IEPE sensors.
Figure 4.6 NI WLS-9234[17]
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5.2 How to acquire sound pressure signal through DAQ?
As can be seen in figure 8.5, compressor built air pressure, is passed in an acoustic horn which is
kept at 1 m distance from the microphone. This acoustic horn produces sound pressure which is
received by the microphone. NI 9234 collects the sound pressure signal in its analog form, from
the microphone which is then converted to digital form by the same. Lab view software is then
used to interpret the data collected by the NI instrument. Figure 8.6 shows the real time acoustic
setup.
Figure 4.7 Line Diagram for Data Acquisition of Sound Pressure[15]
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Sound And Its Different Ways Of Measurement
RESULTS
ON PC
HORNADC and
CHASSIS
Sensor(Microphon
Fig 4.8 Acoustic Data Acquisition Setup[15]
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Sound And Its Different Ways Of Measurement
CHAPTER 6
APPLICATION OF SOUND WAVES
Ultrasonic Cleaning
Ultrasonic cleaning is oldest industrial application of power ultrasonic. Ultrasonic
cleaning works best on relatively hard material such as metals, glass, ceramic and plastics
which reflect rather than absorb sound. Both cavitations and the agitation of the fluid by
the waves are entailed in the process of ultrasonic cleaning. Very delicate parts that can
be damaged by cavitations are cleaned by wave agitation at much higher frequencies,
from 100 kHz to 1 MHz
Flaw Detection and Thickness Measurements
A method of nondestructive testing, the pulse technique, is used extensively to determine
the propagation constants of solids, particularly in the MHz frequency range. This
method consists of sending a short train of sound waves through a medium to a receiver.
In the transmission mode of the pulse technique, the receiver is placed at a measured
distance from the source. In the echo mode, a reversible transducer acts as both source
and receiver, with a reflector used to reflect the pulses. The speed of sound in a medium
can be determined from the time of travel of the pulse over a given length of acoustic
path.
Determination of Propagation Velocity and Attenuation through an Interferometer
The interferometer is a continuous wave device that can accurately measure velocity and
attenuation in liquids and gases that can sustain standing waves.
Ultrasonic Delay Lines
Delay lines are used to store electrical signals for finite time periods. These are used in
computers to store information to be extracted for a later stage of calculation. A method
for generating the delay is to convert those signals into ultrasonic waves that then travel
through a material to be reconverted into their original forms.
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Sound And Its Different Ways Of Measurement
The Ultrasonic Flow meter
The Doppler principle constitutes the operating basis of the ultrasonic flow meter. Two
reversible transducers are submerged in the liquid along the line of flow. One transducer
acts as a signal source of ultrasonic pulses and the other acts as a receiver. At short
regular intervals the roles of the transducers are reversed, so that the source becomes the
receiver and the receiver becomes the source. The wave velocities are c + u along the
direction of the flow and c u in the opposite direction, where c represents the
propagation velocity of sound in the fluid and u the velocity of the streamline flow of the
liquid.
Motion and Fire Sensing
One of the few ultrasonic applications in open air is that of the motion and fire sensor,
which is restricted to the lower kilohertz range, where attenuation is not very much. A
magneto-strictive transducer placed at some point in a room emits pulses in all directions.
The reflected signals from the walls and furniture are eventually picked up by a receiver,
from which a constant indication is generated. Any variation in the sound field, caused by
an intruder or a change in temperature, gives rise to a change in this indication, which
triggers an alarm.
Acoustic Cleaner
The function of an acoustic cleaner is simple; compressed air is introduced through a
specific orifice and causes the titanium diaphragm to flex. The flexing causes a pressure
pulse to be produced that is then amplified by the bell. The length and flare constant of
the bell is what determines the fundamental frequency. The sound pressure produced by
the bell causes particulate deposits to resonate and dislodge. Once dislodged, the material
is removed by gravity and/or gas flow.
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Sound And Its Different Ways Of Measurement
CHAPTER 7
CONCLUSION
Sound is an important part of our day to day life. It has large application in industry too.
Measurement of sound gives the information which can be studied. Basic of sound is
studied here. Different types of transducer and sound sensor is learned. In that
microphone is mainly used. Different instruments used for sound measurement studies
have been discussed. Sound pressure level (db) is normally measured with the help of
Sound level meter at the place of application. Noise dosimeter is used for measurement of
individual noise level. Sound waves when requires a high depth of study then, the
Frequency analyzer is used. The DAQ is used to measure physical characteristics, as well
as for the post processing of sound waves. Hence, the DAQ stands out as a very efficient
instrumentation tool for sound measurement. In this way all type of sound measuring
instruments have been studied in this report.
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REFERENCES
[1] Dr.-Ing. GerhartBor , Dipl.-Ing, Stephan Peus, Microphones for Studio and Home-
Recording Applications, Fourth Edition: 1999, Druck-Centrum Frst GmbH, Berlin
[2] BereniceGoelzer, Colin H. Hansen and Gustav A. Sehrndt, Occupational exposure to
noise: evaluation, prevention and control, WHO Publication, 1995.
[3] http://www.worksafebc.com/publications/health_and_safety/by_topic/assets/pdf/occupati
onal_noise_surveys.pdf.
[4] Ron Bertrand, Online Radio& Electronics Course.
[5] W.C. Jones, Condenser and carbon Microphone Their Construction and Use Bell
System Technical Journal, Volume 10, Issue 1, pages 4662, January 1931.
[6] Richard Payne, Uncertainty Associate with the Use of Sound Level Meter,NPL Report
DQl-AC002, April 2004.
[7] Dennis A. Giardino, John P. Seiler, Noise Dosimeters: Past, Present and Future,
Informational Report 1049, Pittsburgh Technical Support Center, Pittsburgh.
[8] Daniel R. Raichel, The Science andApplication of Acoustics,USA: Springer, 2006.
[9] John Park & Steve Mackay, Practical DataAcquisition for Instrumentation and Control
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