Dahua HDCVI DVR audio Outpur Problem

[sawakura 0]

Hi everyone

I install a HCVR5108H-S2, now i want to connect a speaker to DVR, so i can talk to my worker on the field.

I bought a 2.0 Speaker, it only have a 3.5mm jack, so i use a 3.5mm to RCA adapter like this one

When i plug into the DVR, it arouse squeaking sound even i set the volume at 10%. I tested the speaker with my dvd player, it work flawlessly

How can i resolve the problem