Electrical Engineering Signals problem

[c3real]

Assistance on the below question are very very much appreciated! :D Been pondering about them for quite some time.


Problem: A sensor was placed on a car engine to record its vibration. If the speed of the engine is 4rev/s. Which of the following is true?
A. The amplitude spectrum of the signal is symmetrical about f=0
B. The phase spectrum is not important in determining the vibration heard.
C. The amplitude spectrum will exhibit spikes at multiples of 4Hz.
D. All of the above

My guess: D
Explaination: A is correct because the signal is real. therefore amp spect is symmetrical.
B is correct because for human ears, the phase spectrum is not important for sound recognition. C is correct because the engine is vibrating at 4Hz, therefore the sound components are multiples of 4Hz.


Problem: A 5Hz sinusoid is convolved with a rectangular pulse of width 7.1s. What is the result?
A. sinusoid with period 0.2s
B. periodic square wave of period 0.2s
C. sinusoid of 7.3s
D. none of the above

My guess: D
Explaination: 7.3/0.2 has a remainder of 0.1. Which implies that result will not be a 'easily described' waveform. With noise components towards the end.


Problem: A signal generator and a dual trace oscilloscope are available. Which of the following statements is likely to be correct on the task of measuring the reponse of an optical fibre system?
A. Magnitude response can be measured.
B. Impulse response can be measured
C. All of the above
D. None of the above.

 

[Valkarie]

My guess: CExplaination: The signal generator and dual trace oscilloscope are capable of measuring both the magnitude and impulse response of the optical fibre system.