Compress

With recordings that have a wide range of average volume between different segments, compression can lower the louder parts, leaving the quieter parts untouched. This will allow you to get a more even volume level overall.

Select Effects | Dynamics to open the dialog for compression settings.

Select a threshold a little bit higher than the peaks of quieter segments. This is often around -6 dB, but will vary according to the sound source. Uncheck the Auto Gain correction, and experiment with ratios around 4:1. Again, be sure to check the Create Undo option.

Listen to the sample sound after Compression