Audition CS6 - Vocal scratch spikes

Hello

I do all adjustments using headphones.

I then save the audio - and the adjusted audio replaces the former within Premier Pro.

What I notice is that with the headphones covering the ears that the audio is clean without artifact.
However, if I unplug the headphone and play the video through the computer's external speakers there is this annoying scratching spike. Not overwhelming but it is there.

Do I trust the headphones? or should I be influenced by the external speakers?

I had plans to upload this video to Youtube but now I have this nag over the external speakers delivering that sharp shrill spike as the speaker gives forth the lecture .

Let me k now.

Thanks!