Continuing route canalysis -
You should check the software compatability of the discs your playing
Some CD players do have problems reading certain material (especially older models), and the result can be a distorted signal. For example there are CDs that've been recorded in the DSD (Direct Stream Digital) format. Sony did a limited release of these CDs, although their maintstream DSD format is SACD. Point is, some CD players have real problems reading these and other non-mainstream formats such as HDCD encoded discs with the result of sonic anomolies such as the 'phut phut phut' helicopter sound you hear.
Have you checked if this problem occurs with all discs, or just one or two?Look on the label of your CD(s) that seem to be having the problem, and see if any are non-mainstream formats, such as DSD or HDCD.
If you get no luck on this, perhaps you could check polarity of wiring, and make sure all interconnects are connected in the correct Left Right inputs/outputs.
Cheers BigEars
O'Shag
Austin Powers of Audio