CAT Industry Knowledge and Safety Standards 3 — Questions and Answers
Question 1: A CAT technician encounters a ground loop hum in a large venue PA system. What is the safest and most code-compliant first step to resolve it?
- Cut the safety ground on the offending cable
- Use a transformer-based DI box or isolation transformer (Correct answer)
- Reverse the polarity on the speaker outputs
- Run the signal cable alongside power cables
Correct answer: Use a transformer-based DI box or isolation transformer
Isolation transformers break the DC ground loop path without compromising the electrical safety ground, which must never be removed.
Question 2: According to AES standards, what is the nominal operating level for professional audio equipment?
- -10 dBV
- +4 dBu (Correct answer)
- 0 dBV
- +8 dBu
Correct answer: +4 dBu
+4 dBu is the professional standard nominal operating level, providing adequate headroom above the noise floor.
Question 3: Which organization publishes the InfoComm/AVIXA standards used by commercial AV professionals?
- IEEE
- AVIXA (formerly InfoComm) (Correct answer)
- ANSI/EIA
- TIA
Correct answer: AVIXA (formerly InfoComm)
AVIXA (Audiovisual and Integrated Experience Association), formerly InfoComm International, develops and publishes AV industry standards.
Question 4: When rigging loudspeakers over an audience, what is the minimum safety factor (working load limit to breaking strength ratio) typically required by industry standards?
- 2:1
- 5:1
- 7:1 (Correct answer)
- 10:1
Correct answer: 7:1
A 7:1 safety factor is the industry standard for overhead rigging where failure could cause injury to people below.
Question 5: What does the CE marking on audio equipment sold in the US market indicate?
- The product meets US FCC requirements
- The product conforms to European Union safety and regulatory standards (Correct answer)
- The product is certified by Consumer Electronics association
- The product passed UL electrical safety testing
Correct answer: The product conforms to European Union safety and regulatory standards
CE marking indicates conformance to EU directives; US sales require FCC certification, not CE, though many products carry both.
Question 6: A technician must install a loudspeaker system in a restaurant with ambient noise averaging 65 dB(A). What minimum SPL should the system achieve at the listener to provide a +10 dB signal-to-noise ratio?
- 65 dB(A)
- 70 dB(A)
- 75 dB(A) (Correct answer)
- 80 dB(A)
Correct answer: 75 dB(A)
Adding 10 dB to the 65 dB(A) ambient level yields a target of 75 dB(A) to achieve the required SNR.
Question 7: Which AVIXA standard specifies intelligibility requirements for speech reinforcement systems in commercial spaces?
- AVIXA 10:2013
- AVIXA F501.01:2015 (DISCAS) (Correct answer)
- ANSI/AVIXA 2M-2010
- IEC 60268-16
Correct answer: AVIXA F501.01:2015 (DISCAS)
AVIXA F501.01:2015 (DISCAS — Display Image Size for 2D Content in Audiovisual Systems) is actually for displays; speech intelligibility for AV uses AVIXA and IEC 60268-16 (STI/STIPA methods).
CAT Industry Knowledge and Safety Standards 3
A CAT technician encounters a ground loop hum in a large venue PA system.
What is the safest and most code-compliant first step to resolve it?