Yes. But also if they are already hosted somewhere, most clients play directly most of the media links, posted in notes like this for example (first chapt of Treasure island on librivox). Eventually someone may make a specific audiobook client over nostr with dedicated nostr kind for this. But for now depending size and format you can upload them if you like to a blossom server, nostr.build , nostrcheck.me , cdn.satellite.earth etc.