The bots already know how to work with the audio change that they go little by little change the audio put something better
I don't know if it's really the bots are to be blamed, but I know there are sites that pays bitcoin/satoshis directly to a certain microwallet to people solving XRB captchas/audio captchas and they still exists today. Some people actually choose to use them because they pay bitcoin directly but at a lower rate.