Sound Measurement Final

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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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RESULTS

ON PC

HORNADC and

CHASSIS

Sensor(Microphon

Fig 4.8 Acoustic Data Acquisition Setup[15]


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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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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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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

System,Newness Publications, 1st

Edition 2003, pg. 01-66.

[10] http://homepages.wmich.edu/~hillenbr/206/ac.pdf

[11] Hans-Petter Halvorsen, DataAcquisition in LabVIEW,Telemark University College,

2013.08.16


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[12] https://ccrma.stanford.edu/courses/192a/2-Microphones.pdf

[13] http://chinpen.net/blog/page/5/

[14] http://www.aes.org/sections/pnw/reference/basics_of_sound.pdf

[15] Adnan Sheikh, Experimentaland Simulation Study of Different Horn Amplifier Length

for Cleaning, M.E (Machine Design)Report, FCRIT, Vashi, 2013.

[16] Hans-Petter Halvorsen, WirelessData Acquisition in LabVIEW, Telemark University

College, 2011.02.03

[17] http://www.ni.com/pdf/manuals/374238c.pdf

[18] http://criticalrecordingstudio.com/blog/dynamic-vs-ribbon-vs-condenser/

[19] http://www.mediacollege.com/audio/microphones/dynamic.html

[20] http://physics.tutorvista.com/waves/sound-reflection.html

[21] http://www.thinksrs.com/downloads/PDFs/ApplicationNotes/AboutFFTs.pdf

[22] http://www.ehow.com/list_6633025_advantages-disadvantages-magnetic-tapes.html

[23] Warrington, McLoughlin, Evaluation of Occupational Noise Exposure- Advantages and

Disadvantages of Noise Dosimeter versus Sampling Using a Sound Level Meter,

Proceeding of ACOUSTICS, 9 November 2005.


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Documents

Sound Measurement Final