Abstract – Acoustic sound, pilotage and ranging ( SONAR ) are normally used for submerged measuring applications. The most popular underwater applications utilizing acoustic echo sounder is plumbing appraising which echo sounder is to measured deepness. Depths in acoustic echo sounder are computed based on sonar equation. In sonar equation, elapsed clip from detector conveying echo sounders wave to the underside and reflected back to the detector were measured. The chief parametric quantity lending in calculation of deepness utilizing acoustic echo sounder are travels clip and velocity of sound ( SOS ) . If SOS accurately known, deepness can accurately find. The values of SOS are assorted depend on the temperature, salt and denseness. There are assorted equipments and expression can be used to find SOS accurately. This paper will discourse on field observation of SOS value at different types of H2O ( sea H2O, estuary and fresh H2O ) and analyzed the mistakes in deepness if carry oning work traversing at different types of H2O.

Introduction

In field of hydrography, Bathymetry is most popular technique used in depth measuring. This technique normally called sounding. Sounding can be carried out utilizing assorted method and system such as mechanical method ( Lead line and sounding pole ) and acoustic method ( individual beam reverberation sounder ( SBES ) and multi beam reverberation sounder ( MBES ) ) . Several book explicate more item on these method and system. Ingham ( 1975 & A ; 1987 ) , Poerbandono and Djunarsjah ( 2005 ) , USAGE ( 2002 ) , IHO ( 2008 )

Figure 1: Depth measuring utilizing acoustic echo sounder rule

We Will Write a Custom Essay Specifically
For You For Only $13.90/page!


order now

Most of hydrographic instrument or system used sonar rule in mensurating deepness. The Fig. 1 shows the basic rule of depth measuring utilizing acoustic echo sounder.

In depth finding utilizing acoustic echo sounder, travel clip of acoustic echo sounder transmitted from transducer to the bottom surface and reflected back are measured. By utilizing following equation deepnesss can easy computed:

( 1 )

From the equation ( 1 ) , it clearly shown that to go clip and velocity of sound is the major part to find accurate deepness. Travel clip of acoustic echo sounder can be accurately measured utilizing echo sounder nevertheless velocity of sound may be measured accurately utilizing direct ( Velocity profiler or Conductivity, Temperature and Depth detector ) or indirect method ( saloon cheque and empirical expression ) . It means that the velocity of sound demand to find accurately to do certain computed deepness is accurate.

Speed of sound in H2O is variable due and depends on the temperature, salt and denseness. ( Alkan et Al, 2006, Jamshidi 2010 ) . In the other words, value velocity of sound non consistent when propagate through different types of H2O. Study of velocity of sound are need cause of most of echo sounder equipments need to puting and change the velocity of sound value. The purpose of this survey was to place the value of velocity of sound at the assorted types of H2O ( sea H2O, estuary and fresh H2O ) and eventually analyzed the mistakes in deepness if carry oning work traversing at different types of H2O.

survey country

This survey was carried out at 3 different locations based on the purpose of the the survey. For sea H2O observation, analyze country is located at Pantai Marang, Terengganu ( Fig. 2 ( a ) ) , Taman Tasik Shah Alam, Selangor ( Fig. 2 ( B ) ) for fresh H2O observation and Kuala Terengganu, Terengganu ( Fig. 2 ( degree Celsius ) ) for estuary observation country.

The point marked on the on the map are the approximative location whereby each point are the location of the velocity of sound observation was conducted. The points are located by utilizing a handheld GPS.

Figure 2 Study Area

Field observation and calculation

In order to obtain velocity of sound at the survey country, the flow chart of field observation are constructed and shown at Fig. 3. There are three different location were selected for the three types of H2O that is sea H2O, fresh H2O and estuarine site. Firstly informations are collected at sea H2O at 10 different points. The intent of roll uping informations at assorted points is to happen the mean sound speed informations for each type of H2O followed by sound speed at estuarine site and fresh H2O. For fresh H2O, the observation was conducted at two different times that is at dark and twenty-four hours clip. These observations are merely conducted at the fresh H2O to place the consequence of velocity of sound at different temperature at the surface of H2O.

Figure 3 Filed Observation Method

Speed of sound informations were measured utilizing portable sound speed profiler ( Digibar Pro ) developed by ODOM at all proposed location. The investigation was set in times data acquisition manner and lowered the investigation from the surface bed to the bottom bed ( Fig 4. )

Figure 4 Stairss in take downing investigation

The value of velocity of sound can be determined by utilizing empirical expression, by utilizing the Density or Depth ( D ) , Temperature ( T ) and Salinity ( S ) . All this value can be measured or reciprocally calculated utilizing several different types of instruments. In this survey, the value of denseness, temperature, salt reciprocally calculated utilizing sound speed profiler ( SVP ) equipment. There is several Numberss of equations available to cipher the velocity of sound in H2O from the less accurate ( simples equation ) to the most accurate ( complicated equations ) . The most popular and accurate equation for ciphering sound of speed are Chin and Millero ( 1977 ) , Del Grosso ( 1974 ) , Makenzie ( 1981 ) and Medwin ( 1975 ) ( Alkan et al, 2006 ) . In this survey, velocity of sound is estimated based on simple equation non a complicated equation ( Del Grosso, Makenzie and Medwin ) .

Del Grosso ( 1974 ) equation.

Del Grosso equation has a more restricted scope of cogency. Range of cogency for temperature is from 0 to 30 A°C, salt 30 to 40 parts per 1000, force per unit area 0 to 1000 kg/cm2. This equation used as an option to UNESCO algorithm. Following equation already reformulated for new 1990 International Temperature Scale ( wong and zhu, 1995 ) and their version is:

degree Celsius ( S, T, P ) = C000 +a?†CT +a?†CS +a?†CP +a?†CSTP ( 2 )

where,

a?†CT ( T ) = CT1T + CT2T2 + CT3T3

a?†CS ( S ) = CS1S + CS2S2

a?†CP ( P ) = CP1P + CP2P2 + CP3P3

a?†CSTP ( S, T, P ) = CTPTP + CT3PT3P + CTP2TP2 + CT2P2T2P2 + CTP3TP3 +CSTST + CST2ST2 + CSTPSTP + CS2TPS2TP + CS2P2S2P2

* T = temperature in grades Celsius, S = salt in Practical Salinity Units, P = force per unit area in kg/cm2

The coefficients value of the Del Grosso equations are shown in table 1.

Table 1: Coefficients in the Del Grosso equation for ciphering velocity of sound

Coefficients

Numeric values

C000

1402.392

CT1

5.01E+00

CT2

-5.51E-02

CT3

2.22E-04

CS1

1.33E+00

CS2

1.29E-04

CP1

0.1560592

CP2

2.45E-05

CP3

-8.83E-09

Central time

-1.28E-02

CTP

6.35E-03

CT2P2

2.66E-08

CTP2

-1.59E-06

CTP3

5.22E-10

CT3P

-4.38E-07

CS2P2

-1.62E-09

CST2

9.69E-05

CS2TP

4.86E-06

CSTP

-3.41E-04

Makenzie ( 1981 ) equation.

Makenzie equation is more simple compared to Del Grosso equation but still has a restricted in scope of cogency. This equation used a map of temperature, salt and deepness. The different between Makenzi, Chen & A ; Millero and Del Grosso is utilizations of deepness in the equation. Range of cogency for temperature is from 2 to 30 A°C, salt 25 to 40 parts per 1000, depth 0 to 8000m.

degree Celsius ( D, S, T ) = 1448.96 + 4.591T – 5.304 ten 10-2T2 +

2.374 ten 10-4T3 + 1.340 ( S-35 ) + ( 3 )

1.630 ten 10-2D + 1.675 ten 10-7D2 –

10-2T ( S – 35 ) – 7.139 ten 10-13TD3

*T = temperature in grades Celsius, S = salt in parts per 1000, D = deepness in meters

Medwin ( 1975 ) equation.

This equation is the simplest equation in calculating velocity of sound. Medwin equation is given as:

degree Celsiuss = 1449.2 + 4.6T a?’ 0.055T 2 + 0.00029 T 3 +

( 1.34 a?’ 0.010T ) ( S a?’ 35 ) + 0.016 D ( 4 )

*T = temperature in grades Celsius, S = salt in parts per 1000, D = deepness in meters

This equation is valid for realistic combinations of Temperature, Salinity and Depth. The scope of cogency of Medwin equation in the scopes, temperature 0 to 35 A°C, salt 0 to 40 parts per 1000 and deepness 0 to 1000 m. By utilizing this equation all the parametric quantities must measured accurately ( Alkan et al 2006 ) .

Speed of sound utilizing svp

Speed of sound at sea H2O

Table 2: Value velocity of sound at sea H2O utilizing sound speed profiler equipment

Depth

Sos

Salt

Temp

A

( m/s )

( ppt )

( OC )

0

1546

30.7

33

0.5

1546

30.6

33

1

1546.1

30.3

33

1.5

1546.1

30.2

33

2

1546.1

30.2

33

2.5

1546.1

30.3

33

3

1546.1

30.3

33

3.5

1546.1

30.3

33

4

1546.1

30.2

33

4.5

1546.1

30

33

5

1546.1

29.8

33

5.5

1546.2

29.9

33

6

1546.2

30.1

33

Average

1546.1

30.2

33

Table 2 shows the consequences of mean value velocity of sound straight measured at the sea H2O depth 0- 6 metre utilizing sound speed profiler. The velocity of sound every deepness shown at the tabular array 2 is based on the mean value of 10 different points of observations at the survey country. The consequence shown that the value velocity of sound is non holding important increased from depth 0-6 metres at sea H2O. The mean value velocity of sound at estuarine site is 1546.1 m/s with regard the mean temperature of 33oC and the norm of salt of 30.2 ppt.

Speed of sound at Estuarial site

Table 3: Value velocity of sound at Estuarial Site utilizing sound speed profiler equipment

Depth

Sos

Salt

Temp

A

( m/s )

( ppt )

( OC )

0

1523.1

13.4

30

0.5

1523.4

13.7

30

1

1525.1

15.4

30

1.5

1526.9

17.7

30

2

1531.6

21.6

30

2.5

1533.9

24.2

30

3

1536.5

26.4

30

3.5

1537.7

27.8

30

4

1539.6

29.7

30

4.5

1540

29.6

30

5

1541

30.3

30

5.5

1541.3

30.9

30

6

1541.5

30.9

30

Average

1534

24.0

30

The mean value velocity of sound at estuarine site from depth 0-6 metres is 1534 m/s as shown at table 3. The velocity of sound every deepness is based on the mean value of 10 different points of observations at the survey country. From the consequence, value velocity of sound shown significantly increases when the H2O deepness and salt of H2O addition. However the value of temperature is staying changeless at 30oC at all deepness.

Speed of sound at fresh H2O

Table 4: Value of velocity of sound at fresh H2O utilizing sound speed profiler equipment

Depth

Sos

Salt

Temp

A

( m/s )

( ppt )

( OC )

0

1515.7

0

33

0.5

1515.7

0

33

1

1516.2

0

33

1.5

1516.5

0.2

33

2

1516.8

0.7

33

2.5

1517.3

1.7

33

3

1517.9

1.8

33

3.5

1518

1.8

33

Average

1517

0.8

33

In the tabular array 5, the consequences shows mean value velocity of sound straight measured at the fresh H2O for deepness at scope 0-3.5 metres. The velocity of sound every deepness is based on the mean value of 7 different points at twenty-four hours and dark observations. From the consequence, it shown that the value velocity of sound is increased around 0.1-0.5 m/s at scope of depth 0-3.5meters. The mean value of velocity of sound at fresh H2O is 1517 m/s with regard the mean temperature of 33oC and the norm of salt of 0.8 ppt.

velocity of sound based empirical equation

Table 5 shows the value of velocity of sound at three different empirical equation and differences with the value straight collected utilizing SVP at sea H2O, estuarine site and fresh H2O. From this tabular array 5 ( a ) , the difference value velocity of sound calculated utilizing empirical equation and value from SVP at the scope 0.2-0.5 m/s at sea H2O. Del Grosso equations showed the highest differences meanwhile Medwin equation showed the lowest difference at sea H2O.

Table 5 ( B ) shows, the differences value of velocity of sound calculated utilizing empirical equation and direct measuring utilizing SVP at estuarine site. The value velocity of sound has shown changeless between calculated utilizing empirical equations and straight measured.

At the fresh H2O, value velocity of sound utilizing Del Grosso equation and value from SVP has same value of 1516.7 m/s. However, by utilizing Medwin and Makenzie equation, the value of differences between calculated and direct measuring is at range 0.1-0.3m/s as shown at table 5 ( degree Celsius ) .

Table 5: Comparison value of velocity of sound utilizing equation and SVP at ( a ) Sea H2O ( B ) Estuarial site ( hundred ) Fresh H2O

( a )

Equation

Sos

SOS ( SVP )

DIFF

A

( m/s )

( m/s )

( m/s )

Del Grosso

1546.6

1546.1

0.5

Mackenzie

1546.5

1546.1

0.4

Medwin

1546.3

1546.1

0.2

( B )

Equation

Sos

SOS ( SVP )

DIFF

A

( m/s )

( m/s )

( m/s )

Del Grosso

1534.1

1534

0.1

Mackenzie

1534.1

1534

0.1

Medwin

1534.2

1534

0.2

( degree Celsius )

Equation

Sos

SOS ( SVP )

DIFF

A

( m/s )

( m/s )

( m/s )

Del Grosso

1516.7

1516.7

0

Mackenzie

1517

1516.7

0.3

Medwin

1516.6

1516.7

0.1

Decision

Value velocity of sound at sea H2O, estuarine site and fresh H2O was discuss and presented in this paper. These consequences of survey give utile information for preliminary phase for sounding intents. With this value, hydrographer will salvage clip in choosing suited velocity of sound in graduating echo sounder equipment. The consequence showed the value velocity of sound at sea H2O is 1546.1m/s, estuarine site is 1534 m/s and fresh H2O is 1517 m/s. From this survey, salt is major part in finding of velocity of sound at the survey country.

x

Hi!
I'm Niki!

Would you like to get a custom essay? How about receiving a customized one?

Check it out