VDV Audio/Video Systems Installation 4 — Questions and Answers
Question 1: Which tool is used to verify that an HDMI cable will support 4K/60Hz signals before installation in a finished wall?
- Cable certifier (e.g., Fluke DSX)
- HDMI signal tester/verifier (Correct answer)
- Tone generator and probe
- Optical power meter
Correct answer: HDMI signal tester/verifier
An HDMI signal tester verifies that the cable can carry 4K/60Hz by checking bandwidth, HDCP handshake, and signal integrity.
Question 2: What is the purpose of a ground loop isolator in an audio system?
- To prevent speakers from being driven below their impedance rating
- To eliminate the 60Hz hum caused by different ground potentials between equipment (Correct answer)
- To boost low-frequency signals in a subwoofer system
- To protect against lightning strikes on exterior cable runs
Correct answer: To eliminate the 60Hz hum caused by different ground potentials between equipment
A ground loop isolator uses a transformer to break the DC path between two pieces of equipment, eliminating hum caused by ground potential differences.
Question 3: A rack is running hot and equipment is shutting down due to thermal protection. What is the FIRST corrective action a technician should take?
- Replace all equipment with lower-power models
- Add a rack-mount exhaust fan and verify adequate front-to-back airflow (Correct answer)
- Move the rack to a cooler room
- Reduce the number of active HDMI cables
Correct answer: Add a rack-mount exhaust fan and verify adequate front-to-back airflow
Installing a rack exhaust fan and ensuring proper front-to-back airflow is the most immediate and effective solution for rack thermal issues.
Question 4: When installing a home theater surround sound system, what is the recommended placement angle for surround speakers relative to the primary listening position?
- Directly behind at 180 degrees
- 90 to 110 degrees to the side (Correct answer)
- 45 degrees in front
- 60 degrees behind
Correct answer: 90 to 110 degrees to the side
Dolby and DTS recommend placing 5.1 surround speakers at 90–110 degrees to the sides of the listening position for optimal envelopment.
Question 5: What does 'signal-to-noise ratio' (SNR) measure in an audio system?
- The ratio of speaker power to amplifier power
- The level of the desired signal compared to the level of background noise (Correct answer)
- The ratio of treble to bass in the audio spectrum
- The impedance mismatch between source and load
Correct answer: The level of the desired signal compared to the level of background noise
SNR measures how much stronger the desired audio signal is compared to the unwanted noise floor, expressed in decibels (dB).
Question 6: Which type of video cable uses a threaded locking connector and is the professional broadcast standard for HD-SDI signals?
- HDMI Type A
- DisplayPort
- BNC coaxial (Correct answer)
- DVI-D
Correct answer: BNC coaxial
BNC connectors are the standard for SDI and HD-SDI coaxial video cables in professional broadcast and AV installations due to their secure locking mechanism.
Question 7: A technician is installing a projection screen and needs to calculate the correct screen size. The room is 24 feet deep and the farthest viewer is at 20 feet. Using the 2H rule, what is the minimum recommended screen height?
- 5 feet
- 10 feet (Correct answer)
- 12 feet
- 24 feet
Correct answer: 10 feet
The 2H rule states the farthest viewer should be no more than 2 times the screen height away, so 20 feet ÷ 2 = 10 feet minimum screen height.
VDV Audio/Video Systems Installation 4
Which tool is used to verify that an HDMI cable will support 4K/60Hz signals before installation in a finished wall?