Measure phone call delay using Audacity

Audacity Help Forum Windows
1

I’m working on a project to replace a customers phone system - they are reporting intermittent audio delay/latency on calls from some customers

I want to find a way to measure the end to end delay so we can get an accurate measurement

Someone suggested recording both ends of the calls so measure the delay

Does anyone have any experience or advise on how to best do this?

2

I’m assuming that you mean a landline system.

Unless you represent the telephone service provider, any latency in the telephone system between the two properties is beyond your control. The only latency that you have any control over is the latency within the system that you are supplying.

It would therefore be acceptable for both ends of the call to be within your client’s premises, provided that they have at least two independent telephone numbers. Note: You will not get an accurate measurement from a cell phone.

You will need to call from your new system, and receive the call in the same room with a standard land line telephone.

  1. Place the recording microphone close to the earpiece of the standard landline telephone.
  2. Call the landline number from the new system.
  3. Start recording.
  4. Make a loud, abrupt sound (such as a balloon pop, or clapper board) near to the mouthpiece of the new system.
  5. The recording should pick up the direct sound from the balloon / clapper board, followed by the sound from the receiving telephone.
  6. The recording should show two peaks, one from the direct sound and one from the receiving telephone - the distance between the peaks is the latency (Mouth-to-ear delay).
3

I’m working on a project to replace a customers phone system - they are reporting intermittent audio delay/latency on calls from some customers

What kind of phone system? Land-Line systems have nearly zero delay and timing problems when communicating with other land-line systems. However, when they’re communicating with badly designed or busy VOIP digital systems, the delay can be crazy. That’s the first thing that crossed my mind when I read your post. Nothing the client is going to do is going to make some delays vanish. They’re built into the “other end.”

For a VOIP, the first thing you should do is find out the quality of their internet connection. My home system is a salty, wet string between here and the central office and won’t support any good quality, live, fast, outgoing sound, no matter what the software.

If they’re already on a VOIP system, you can make many delays vanish by reverting to a classic land-line.

For testing, see Steve, above. Many times, trying to record round trip impulse sound (Clap) is foiled by the system echo cancellation, so you have to use two systems.

I had a call from a Land-Line to a Help Office whose delay was so bad we started stepping on each other’s words before I sorted what was happening. Nothing I do can ever make that delay go away.

Koz