How to Tune VICIdial AMD Accuracy When It Is Wrong Too Often

Answering machine detection (AMD (answering machine detection)) is never perfect on day one. It has to be tuned to the kind of leads you dial and the telecom lines you dial through. If AMD is sending real people to a voicemail message or pushing machines to your agents, the fix is rarely to give up. It is to adjust the settings until the decisions match what you actually hear.

Decide what wrong looks like first

There are two kinds of mistakes, and they pull in opposite directions. A false positive (AMD false positive) is when AMD calls a live human a machine and either hangs up or plays a message at a real person. A false negative is the reverse: a machine slips through and an agent (Agent) wastes time listening to a voicemail greeting. Before you change anything, figure out which one is hurting you more, because tightening the settings to fix one tends to make the other worse.

Look at what AMD decided

You cannot tune what you cannot see. The AMD Log Report shows the result the detection function returned on calls placed from your dialers. Pull it for a recent window and compare the logged status (Status (lead status)) against reality on a sample of calls. That tells you whether your problem is too many machines getting through, too many humans getting cut, or both at the edges.

flowchart TD
  A[Call answered] --> B[AMD analyzes audio]
  B --> C{AMD result}
  C -->|HUMAN| D[Send to agent]
  C -->|MACHINE| E[Hang up or play message]
  C -->|NOTSURE| F[Route per your settings]
  D --> G[Check AMD Log Report]
  E --> G
  F --> G
  G --> H[Adjust parameters and retest]

Adjust the AMD parameters

The real tuning happens in the Asterisk AMD application parameters that run when a call goes through the AMD-enabled call processor. These control how long the system listens, how it judges greeting length, and how much silence between words it tolerates before it decides. Tightening them tends to catch more machines but risks cutting humans; loosening them protects humans but lets more machines through. We cover each number in detail in our guide to the AMD Asterisk parameters.

Change one thing at a time. If you adjust three parameters at once and accuracy moves, you will not know which change did it. Make a single change, dial a few hundred leads, pull the log, then decide.

Match the tuning to your traffic

AMD behaves differently across markets. Cell-heavy lists (Lead list) carry more carrier voicemail greetings that sound like people. Different carriers (Carrier) add their own delays and tones. The settings that work for one campaign (Campaign) may be wrong for the next, so tune per campaign rather than chasing one global setup.

Consider whether you need AMD at all

AMD adds processing time to every call, not only the ones that turn out to be machines. For a lot of campaigns a simpler approach works better: set the Dial Timeout to around 22 to 26 seconds so the call drops before most voicemails pick up. Compare the two approaches in our breakdown of AMD versus Dial Timeout, and read the full picture in the AMD and CPD complete guide.

Tuning AMD takes iteration, and it is easier when someone else handles the Asterisk side. VICIfast manages the dialplan, the AMD application, and the audio store so you can focus on the numbers in the log. See VICIfast pricing to get a managed dialer with AMD ready to tune.