Finder does show the duration and bit rate for both wav and aiff files on my installation.
You could see if the metadata is shown by mdls or after reimporting some directory with mdimport. Or delete the Spotlight local stores with
sudo mdutil -Ea.
Another way to show information about audio files is to use
$ afinfo /System/Library/Sounds/Basso.aiff
File type ID: AIFF
Num Tracks: 1
Data format: 2 ch, 22050 Hz, 'lpcm' (0x0000000E) 16-bit big-endian signed integer
no channel layout.
estimated duration: 0.164490 sec
audio bytes: 14508
audio packets: 3627
bit rate: 705600 bits per second
packet size upper bound: 4
maximum packet size: 4
audio data file offset: 54
source bit depth: I16