There are many "Audition alternatives", but it's hard to recommend anything without knowing what you want it for. Audacity might be OK if your needs are very basic. Pro-tools is kind of the industry standard DAW. Reaper is sort-of-free and quite popular. Ardour is FLOSS and good (although with paid binaries). Izotope RX9 is brilliant for cleaning up audio clips. Mixbus is supposed to have a great emulation of classic analogue mixers. Hindenburg is popular with podcasters. Etc.