Thank you for your reply.
First and foremost, please be informed that this is a community where everyone is here willingly to help each other on any issues related to using the application and on sharing and discovering music.
Next, the difference between a high quality at 160 kbps (bit rate per second) and 320 kbps is how real a sound can be presented. This has nothing to do with the volume. Here is a video example on 160 kbps vs 320 kbps and here is information writtten by a third party on Spotify's bit rate and streaming quality differences. Lastly, here is a visual representation on differences of sound quality from Quora.com.