How to understand the delay and Latency in the audio system?

In the process of sound information transmission, delay parameter index testing is usually involved. For large audio systems, the smaller the time spent by each device encountered in signal transmission theoretically, and the better the adjustable dynamic range of the system as a whole. Also in large systems, we usually want our DSP devices to be able to provide enough signal delay to process signals to speakers at different distances. Is it inconsistent? In fact, these are two different indicators. To solve the confusion, we need to make a conceptual distinction between them:

In network performance testing, Latency and Delay are generally used as distinctions, and audio signals are the same.

1）Latency

When the signal enters a device and the signal exits the device, the total time required is determined by the circuit, hardware structure design, and algorithm of the device itself. So testing this indicator is actually testing the time it takes for the device to process or pass the signal. Taking the audio processor as an example, it includes audio sampling time, decoding and encoding time, audio processing (AEC\AFC\ANC\AGC ), etc., if the time is shorter and reaches a certain threshold range, then we can consider that the index of this device is good, and the shorter the delay, the better the performance.

The generalized delay can even broaden the scope of the discussion to the entire bypass audio system, the length of time it takes for the sound signal to pass through the sound pickup device (such as a microphone) to the final sound reinforcement speaker,

It can also be used to roughly evaluate the design level of the audio system and whether the equipment selection is reasonable.

2）Delay

The length of time between pauses between signals passing from one module to another.(such as digital audio processors, speaker managers, and the Delay function modules that come with DSP digital power amplifiers) can do active signal pause output for the audio system, and its practical significance is very important for audio workers. When achieving relatively good sound pressure coverage, fill sound or auxiliary speakers will be configured at the back of the venue as a supplement. However, due to the difference in the sound propagation time of different sound reinforcement sources, the sound will be blurred and muddy. Even because of the phase, the sound cancels out and affects the overall sound reinforcement. In this case, use the Delay function of the device to adjust the sound image to achieve consistency.

From the description of the above definition, we can see that no matter the delay or delay, it will eventually have an impact on our evaluation of the good or bad equipment or system, and it is still inappropriate to discuss the performance of two parameters of a single device and module. Audio system designers often combine more complex requirements when making product selection, such as product brand, user experience, cost performance, and so on