I number of times we have been asked what is the easiest way to check if a noisy channel is nosy because of noise on the cable or noise generated by a faulty component on the card. The following is a simple step-by –step process that will tell if the noise is on the cable or generated by a fault on the analogue channel card.
What is a noisy channel?
Typically, if you have an analogue channel set to use VoX as a recording trigger, the channel should not be recording if there is no voice on the line. Sometimes, due to noise on the line, or noise generated by a faulty component on the analogue channel card, recording starts and stops at random times. When you listen to such recordings, typically you will be able to clearly hear noise signals.
To determine if the noise is on the line or generated by a fault on the channel card:
- Disconnect the cable (line) that is connected to the channel.
- For the channel in question, change the recording trigger from VoX to Off-Hook (say Off-Hook 4).
- Recording will start on the channel. Wait for couple of minutes.
- For the channel in question, change the recording trigger back to VoX (the same VoX level as it was before). This will end the recording on the channel.
- Listen to the recording. If you hear mostly silence, then the noise is on the line. If you hear the noise (the same noise as recorded when the line is connected to the channel), then the noise is generated on the card (most likely by a faulty or out-of-spec component on the card).