Speeding up or slowing down a clip introduces metallic noise when adjusting for pitch I'm slowing down some audio. I chose to "Maintain Audio Pitch" because I don't want it to sound like a very deep voice. However, when I play back the audio, it sounds like it's going through a metal filter.

Is there a better way to change the duration of a clip and have it sound more natural?
Most of the time you should not rely on the automatic Maintain Audio Pitch setting because it causes the audio to be distorted (both when speeding up and slowing down). 

Instead, leave that checkbox unchecked, and add one of these filters instead:


Pitch Shifter (Obsolete)
AUPitch


And play around with the settings until it sounds better.

See SPEED UP Video with No Audio DISTORTION in Premiere Pro for more info.