Slowed Down Audio Frequency

It always depends on how much you need to slow down the audio by. The more you do the more artefacts are generated I'm afraid. So it is always a case of juggling with the settings to get the best result for any given audio and how much slow down you can get away with. If you are using the Stretch and Pitch effect in Waveform view there are the two different algorithms available, Audion and iZotope Radius. The two may give different results with different types of audio. So try both.