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1) There is a pipe 100 m long with 1 sensor placed at each end. The constant wave velocity is 3500 m/s. The stress wave hits sensor 1 after 3.94 ms and hits sensor 2 after 24.62 ms. Please find the location of the source from sensor 1 in m truncated to two decimal places.

2) What is the significance if the time difference between hits equals 0?
The source is located at sensor 1.
The source is located at sensor 2.
The source is located outside of the two sensors.
The source is located at the midpoint between the two sensors.
3) If the source is located outside of the area between the two sensors, what effect does this have on the time difference between hits?

It doesn't have any effect. You can still calculate the time difference the same way for source location.
The time difference measurement is equal to the time of flight between the outer sensor pair and an exact source location can't be found.
Find the time difference the same way but make it negative before using it to find the source location.
The time difference equals 0.
4) There is a pipe 11 m long with 1 sensor placed at each end. The attenuation characteristics of the pipe are defined by the following equations:
db=-8x  for  0<=x<=1
db=-2x-6 for x>1
Where x is the distance the sensor is from the source. If the attenuation of sensor 1 exceeds that of sensor 2 by 21.7 db, what is the distance of the source from sensor 1 in m truncated to one decimal place?

5) In acoustic emission, the Kaiser effect may be regarded as a special case of the felicity effect. What felicity ratio does the Kaiser effect exhibit?
1
0
0.5
infinity
6) What is the frequency range for acoustic emission?
between 100kHz and 1MHz
between 20kHz and 300kHz
between 100kHz and 300kHz
between 20kHz and 1MHz
7) In a two dimensional plane, there are three sensors. The distance between sensor 1 and sensor 2 is 100 m with 10º angle from the reference line. The distance between sensor 1 and sensor 3 is 100 m with a 70º angle from the reference line. The constant wave velocity is 3500 m/s. If the time difference between hits of sensor 1 and sensor 2 is 24.8 ms and the time difference between sensor 1 and sensor 3 is 23.9 ms, what is the distance from sensor 1 rounded to one decimal place and the reference angle of the source rounded to the nearest degree?

distance:
angle:
8) Which of the following factors do not tend to increase acoustic emission response amplitude?
low temperature
a material containing discontinuities
homogeneity
large grain size
9) What type of sensor is predominantly used in acoustic emission testing?
capacitive transducers
piezoelectric elements
laser interferometers
10) In a two dimensional plane, there are four sensors. 
Sensor 1 is located at x=1.1 m and y=-3.8 m.
Sensor 2 is located at x=3.6 m and y=-3.9 m.
Sensor 3 is located at x=2.5 m and y=0.1 m.
Sensor 4 is located at x=-0.8 m and y=-0.7 m.
The constant wave velocity is 350 m/s. 
The stress wave hits sensor 1 after 20.97 ms, sensor 2 after 19.48 ms, sensor 3 after 9.21 ms, and sensor 4 after 17.37 ms. What are the x and y coordinates of the source rounded to one decimal place?

x:
y:
11) If the order of arrival of an acoustic emission event to three sensors is the sequence 312, determine the zone where you would find the source.

A      D
B      E
C      F