Common mode choke coil for audio/data line pair recommendation.

I just need a common mode choke coil recommendation and or a part # for the following issue:
1. 12 gauge copper audio pair (underground) that run approx 5ooo' from source to load. The only signal on the pair is a 1440 hz audio tone. Impedance at source and load is the normal 600 ohms.2. Approx 2500' from the source (underground) AC power line noise is getting induced onto the audio pair which causes an extremely noisy signal to arrive at the load. The underground AC power lines feed airfield lighting (approx 120-240 vac).3. I have already troubleshot equip / safety / shield grounding.Any thoughts would be greatly appreciated.  

Hi Chris,you can make a first selection by accessing a distributor's selection page such as this one:https://www.digikey.com/products/en/filters/common-mode-chokes/839
By entering the filter type (power line, signal line, or power and signal line), number of lines and impedance, you can get a first selection of available components. After that, you can choose the device which best fit your specific requirements.

Instead of a common-mode choke, I suggest obtaining two 1:1, 600ohm:600ohm, audio transformers, and connect the two ends of the line through the two transformers to isolate the line from both source grounding and load grounding. The source drives the primary winding of the first transformer. The secondary drives the line. The other end of the line drives the primary of the second transformer. The secondary drives the load. Small 1:1 power transformers would also likely work. Those with plastic barrier between primary and secondary would have less capacitance between primary and secondary. This low capacitance would provide a higher common-mode impedance at 1440 Hz than a reasonable choke would provide, and hence better rejection of common-mode signals.

Thx Peter. I already fabricated 2 600:600 transformers and will be installing next week. I was going to try a CMF dual mode choke as plan B in case the xformers don't work. I just don't know what values to use to select the CMF chokes. All the values I can think of are 600 ohm impedance, approx 740 - 2880 hz audio tones and maybe about 50 ma of noise current. Do you have any thoughts on what values I could use to select a proper choke?

Thx Paul,I will give it a shot.

Your audio pair needs to be in its own conduit separate from any power wiring. A steel conduit will reduce magnetic pickup by your audio pair.