Macos – How to convert WAV to Apple lossless in the terminal

The easiest way to do this is probably with iTunes. In your preferences, go to Import Settings and choose "Import Using" to WAV encoder. Then you can right-click on any AAC song and choose "Create WAV version." You should be able to select a bunch of files at once and do this to them in bulk.

Nota bene: Don't forget to switch your import settings back to AAC when you're done, presuming you still want to be using it.

It is possible the noise you are referring to is dither. Many bitrate conversion algorithms will add dither, which is low amplitude, often frequency-shaped noise to the signal before the conversion. This noise actually increases the audible quality of conversion in most cases. If you don't want dithering, hopefully your application preferences will let you disable it.