CAT CAT Digital Audio and Networking 2 — Questions and Answers
Question 1: In AVB (Audio Video Bridging), what is the role of a 'Talker'?
- The device that originates and transmits audio streams on the network (Correct answer)
- The device that receives and decodes audio streams from the network
- The network switch that manages stream reservation
- The master clock source for the entire AVB network
Correct answer: The device that originates and transmits audio streams on the network
In AVB terminology, a Talker is a source device that advertises and transmits audio streams, while Listeners are the destinations that subscribe to those streams.
Question 2: What is the function of the PTP (Precision Time Protocol) in a networked audio system?
- To synchronize clocks across all devices on the network to a common time reference (Correct answer)
- To prioritize audio packets over video packets on shared switches
- To encrypt audio data transmitted over Ethernet
- To automatically discover and register audio devices on the network
Correct answer: To synchronize clocks across all devices on the network to a common time reference
PTP (IEEE 1588) synchronizes device clocks across a network to sub-microsecond accuracy, ensuring all audio nodes sample and play back audio at the same clock reference.
Question 3: What VLAN practice is recommended when deploying audio-over-IP networks in a commercial installation?
- Segment audio traffic onto a dedicated VLAN separate from general data and management traffic (Correct answer)
- Place all audio and IT devices on the same VLAN to simplify routing
- Disable VLANs entirely and use flat Layer 2 switching for lowest latency
- Use one VLAN for transmit streams and another for receive streams on every device
Correct answer: Segment audio traffic onto a dedicated VLAN separate from general data and management traffic
Placing audio-over-IP traffic on a dedicated VLAN isolates it from general network traffic, reducing congestion and improving reliability and QoS enforcement.
Question 4: What is latency in a digital audio network, and why does it matter in commercial audio systems?
- The delay between audio input and output; excessive latency causes lip sync issues and monitor feedback problems (Correct answer)
- The maximum number of simultaneous audio channels the network can carry
- The bit error rate of the digital audio stream over the network
- The frequency response deviation introduced by codec processing
Correct answer: The delay between audio input and output; excessive latency causes lip sync issues and monitor feedback problems
Latency is the time delay through the audio chain; in commercial systems it affects synchronization between video and audio, creates problems in monitor mixes, and can cause comb filtering in multi-speaker deployments.
Question 5: What does the term 'word clock' refer to in a digital audio studio or live system?
- A master timing signal that synchronizes the sample rate of multiple digital devices (Correct answer)
- The binary word that represents each audio sample in a digital stream
- A clock generator used to derive MIDI timecode
- The internal CPU clock of a digital mixing console
Correct answer: A master timing signal that synchronizes the sample rate of multiple digital devices
Word clock is a square wave reference signal at the system sample rate that all digital devices lock to, ensuring they all sample and convert audio at exactly the same rate to prevent clicks and noise.
Question 6: What is the advantage of using fiber optic cabling for digital audio transport in a commercial installation?
- Immunity to electromagnetic interference and ground loops over very long cable runs (Correct answer)
- Higher audio bit depth than copper Ethernet cables
- Lower latency than copper at distances under 100 meters
- Native compatibility with analog balanced audio without converters
Correct answer: Immunity to electromagnetic interference and ground loops over very long cable runs
Fiber optic cables transmit light rather than electrical signals, making them completely immune to EMI, RF interference, and ground loops, which is critical in noisy commercial electrical environments over long distances.
CAT CAT Digital Audio and Networking 2
In AVB (Audio Video Bridging), what is the role of a 'Talker'?