What are you trying to do?
I’m trying to set 16 khz sound to Queue Join Announcement. (since 8khz quality is too poor).
FreePBX does not support 16 khz sound?
Everything in Asterisk typically lives at 8k mono
No. Old Asterisk support 8 and 16 khz. New Asterisk support up to 192 khz: Home - Asterisk Documentation
FreePBX is like a Ferrari
Asterisk is the F136GT Engine that makes it go vroom
Asterisk typically uses ulaw or alaw which is 8k
Most things in the phone world use 8k. Anything higher would have to be trans-coded to 8k so they use 8k native. If there is a noticeable quality problem (on a phone not your PC) then they were likely down-sampled wrong.
Strange, I’ve never found 8Khz to sound bad in terms of quality. But it does depend how you record the announcements. I always use a professional recording company.
Your softphones are almost certainly using a codec that has a high frequency rolloff filter of 3.5khz.using a higher bitrate that 8KHz requires transcoding and wasted CPU cycles, if you don’t believe me ask Nyquist.