# How sound waves detect faults in girders

1. Jan 13, 2012

### sgstudent

[PLAIN]http://postimage.org/image/4ure9j3sr/[b]1. [Broken] The problem statement, all variables and given/known data[/b]

i have a physics questions about sound Sound waves are used to detect faults in girders. a cro is used to detect these faults, a pulse producer and a detector is placed on opposite sides of the detector.

The safe detector has a upwards spike at 0microseconds and at 10 microseconds.

The unsafe detector has a upwards spike at 0 microseconds and 10 mircroseconds and also one additional but smaller upwards spike at 4 microseconds.

why is the the unsafe detector considered unsafe?

2. Relevant equations

3. The attempt at a solution
my understanding: there is a crack in the girder so when the sound waves is sent in, some of the waves will have to go around it so it causes it to be slower than the sound waves which do pass the crack. because it is slower, so it is shown in the 4 microseconds. meaning that if another pulse is sent out one of the recorded one will be at 10microseconds from the previous one and another which is 4 microseconds ahead of just detected pulse

the image i drew of the CRO is here http://postimage.org/image/4ure9j3sr/
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

Last edited by a moderator: May 5, 2017
2. Jan 13, 2012