As someone who has listened to talk radio programs I was a kid. I can tell you that it is normal for their to be static behind the audio of a interviewee brought in by telephone. This simply happens because the audio quality of an analog telephone line is very bad. Such old technology.
We are taking that audio from that call, that telephone line and amplifying it's imperfections. The problem without the gate is that the static would be there the entire time that the caller's line is open.
The idea is that you bring the caller in and you can keep EVERYTHING except for the caller in Perfect, HIGH STUDIO QUALITY. This is the way talk radio with telephone guests have always been.
Now, it is possible to get some callers who have less static on their lines than others. And of course, you also need to consider your own line phone line as well.
However, despite this static in the back of the audio, the only person this has ever bugged IS ME! Seriously, I've done A LOT of telephone interviews for my podcasts. I'll paste two below for you to sample the quality that I've achieved. Is there static on the line behind the caller? Yep. The audience represented by the two episodes posted below number over 65,000 people who listened.
Do you know how many people complained of the audio quality of my guests? NONE!!!! That's right.. NOBODY COMPLAINED! Why? Because, this is what they expect from a telephone interview. In fact, I received 100's of emails regarding these interviews telling us how AWESOME IT WAS that we had been able to land those interviews.
So have a listen to the links below and tell me if you are able to get audio as good as it.. If not, it could be your phone line.
12 Minutes Into this episode:http://biggestloserpodcast.com/interview-with-ali-vincent/
I would suggest listening at 25 minutes into this episode:http://gspn.tv/pierrechang/