Here are long-time Audible standards for the seconds of pasted room tone to use in each file:
.5 at beginning of file
2.5 after chapter announcement
At least 2 and no more than 3.5 for mid-chapter section breaks designated by ####, ****, ———, or blank space in the text. Even when the text does not include these visual cues, you may need to add this transitional silence to alert the listener of a scene change. The narrator’s pace and type of story can cause this time to vary, but 2-2.5 seconds usually works well.
3.5 at end of file
Some rights holders will ask for a musical interlude or sound effects between chapters. They also may ask for longer pauses than those shown above and/or request that the narrator speak slower throughout the book so that the finished time will reach a certain threshold. Say NO to these types of requests.
Many indie rights holders have not listened to many audiobooks and do not know the norms of production. They also may be unaware of listener expectations. The audiobook’s pacing will be organically derived in the recording sessions and depend on the narrator’s normal rate of speech, acting choices, and complexity of the text. If a narrator speaks too slowly or adds unnecessary pauses, the listener can give up in frustration, leave negative reviews and ratings, and possibly even return the audiobook.