The sound mind engages how what we hear, how we think. The book makes an interesting and impersuasive argument that sound is more than just hearing. A 20 % of the book is references so there's a lot of science to look at.
We undervalue our sense of hearing and we under-appreciate the impact sweet sounds and disturbing noises have on our well-being. Neuroscientist Nina Kraus of Northwestern University talks about her book, Of Sound Mind. Kraus argues that our listening affects our minds and brains in ways we ignore at our peril.