I just completed a build but had no output to display. I hooked up a speaker to the mobo, but I'm not sure what the beep codes mean. It's one short, then a delay of a couple seconds followed by a long beep and three short beeps, another shorter delay and another short beep. I'm guessing it's a video card issue, but the last beep is throwing me off.
Here is a link to a recording of the beeps: https://clyp.it/hf03grau
Build details:
Ryzen 5 3600X
ASUS Prime B550-M A
Gigabyte GeForce RTX 2070 8 GB WINDFORCE 2X Video Card
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Videos
The manual exists on Asus' support site and it contains the beep codes on page 2-16 ("Chapter 2: Getting Started"):

(Motherboard) ASUS BIOS beep codes
- One short beep - VGA detected, No keyboard detected
- Two short beeps - When using Crashfree to recover BIOS, the new BIOS is successfully recognized.
- One continuous beep followed by two short beeps then a pause (repeated) - No memory detected
- One continuous beep followed by three short beeps - No VGA detected
- One continuous beep followed by four short beeps - Failure of Hardware component
One newer FAQ alternatively blames specifically CPU conditions for the latter case.