CAT Technical Skills 2 — Questions and Answers
Question 1: What is the primary purpose of a high-pass filter (HPF) in a commercial audio system?
- Boost high frequencies
- Remove frequencies below a set point (Correct answer)
- Increase overall gain
- Add harmonic distortion
Correct answer: Remove frequencies below a set point
A high-pass filter attenuates frequencies below its cutoff point, allowing higher frequencies to pass through.
Question 2: In a balanced audio connection, which pin carries the negative (cold) signal in an XLR connector?
- Pin 1
- Pin 2
- Pin 3 (Correct answer)
- Pin 4
Correct answer: Pin 3
In standard XLR wiring, Pin 1 is ground, Pin 2 is positive (hot), and Pin 3 is negative (cold).
Question 3: What does 'SPL' stand for in commercial audio?
- Signal Processing Level
- Sound Pressure Level (Correct answer)
- Speaker Power Load
- System Peak Limit
Correct answer: Sound Pressure Level
SPL stands for Sound Pressure Level, measured in decibels (dB), representing the intensity of sound.
Question 4: Which type of microphone uses an externally applied voltage (phantom power) to polarize its capsule?
- Dynamic microphone
- Ribbon microphone
- Condenser microphone (Correct answer)
- Piezoelectric microphone
Correct answer: Condenser microphone
Condenser microphones require phantom power (typically 48V) to polarize the capacitor capsule and power internal electronics.
Question 5: What is the standard impedance for professional audio line-level signals?
- 8 ohms
- 75 ohms
- 600 ohms (Correct answer)
- 10,000 ohms
Correct answer: 600 ohms
600 ohms is the traditional standard impedance for professional audio line-level signals, originating from telephone transmission systems.
Question 6: A technician measures a signal with 10 times the voltage of another signal. What is the dB difference?
- 10 dB
- 20 dB (Correct answer)
- 40 dB
- 100 dB
Correct answer: 20 dB
The formula for voltage gain in dB is 20 × log10(V2/V1); 20 × log10(10) = 20 dB.
Question 7: Which cable type is most appropriate for high-frequency digital audio signals in a commercial install to minimize interference?
- Unshielded twisted pair (UTP)
- Coaxial cable
- Multi-conductor unshielded cable
- Shielded twisted pair (STP) (Correct answer)
Correct answer: Shielded twisted pair (STP)
Shielded twisted pair (STP) provides both the common-mode noise rejection of twisted pairs and additional EMI shielding from the outer shield.
CAT Technical Skills 2
What is the primary purpose of a high-pass filter (HPF) in a commercial audio system?