Audio Effects sound different after export

Hello,

I am trying to design sound in Premiere Prio CS6.

I use audio effects such as Pitchshifter, Bass and Treble to design my sounds. In the timeline, after I have finished adding effects to my sounds, they sound the way I want them to. However, when I export everything, they sound different. Why is that? How can I fix this problem?

I export with these settings:

Format: H.264

Preset: Youtube HD 1080p 23.976

File Type: mp4

Audio Format: AAC

Audio Codec: AAC

Sample Rate: 48000 Hz

Channels: Stereo

Audio Quality: High

Bitrate Settings [kbps]: 256

Precedence: Bitrate

Any help would be appreciated.

Thanks

Kewin