On 1/20/2012 1:39 PM, D. Peter Maus wrote:

They most certainly are used as selling points. That's why they go to
the effort and expense of conducting them.

Actually the purpose was to determine the minimum bit rate at which HD
could be broadcast where listeners still gave it high marks for audio
quality. They performed the bit-rate testing for different genres of
music, and for voice, so stations could determine optimal bit rates for
their HD sub-channels. Most stations chose to not go beyond HD2 (HD1
same as analog channel) and one HD2 music sub-channel. There are areas
where there is voice on the sub-channel (sports, religious broadcasts,
etc) where an HD3 sub-channel is acceptable. Once you get below the mid
40's then listeners perceive lower quality audio.

The mistake many people make is trying to claim that just because the
audio is perceived as near CD quality by listeners, that the compression
scheme actually results in audio that is not near CD quality. The fact
is that the broadcasters care about what their listeners perceive, not
what an audiophile might discern, and not what a techie with a spectrum
analyzer might figure out.

Every in-depth test of HD Radio, and every casual evaluation by testers
from publications like the WSJ and CR confirms that HD Radio audio is
perceived as being much higher quality than FM. Of course much of the
reason for this may be that so much FM sound so bad due to multipath.