[Elecraft] PsychoAcoustics and Delay

[Jim Brown]

On 9/1/2012 5:58 PM, Bill Frantz wrote:
> Thanks for telling us about this "feature".

Psychoacoustics is the study of the human perception of sound, and its 
practitioners are a part of the Acoustical Society of America, of which 
I am a member. The discipline is quite well developed, and what these 
folks had learned as early as 1850 formed the basis of modern stereo 
sound recording and reproduction.  One of the earliest scientists was 
Joseph Henry, inventor of voltmeters and motors, whose name is on the 
unit of inductance.

Sound system professionals have had to deal with electrical delay 
resulting from digital signal processing (called "latency") since the 
early '90s, when DSP came into widespread use in large sound systems, 
and with acoustic delay that results from "time of flight" of sound from 
live musicians on stage and big loudspeaker systems at considerable 
distance (and height) from the musicians. Indeed, managing these delays 
is a critical part of sound system design, especially in large spaces 
and venues.

When listening to a reproduction of our own voice, the human ear/brain 
can tolerate delays up to about 60msec, but begins having fatigue with 
much more than about 50 msec, and begins having serious trouble speaking 
with a delay more than about 80-90 msec.  As a pro audio engineer doing 
a LOT of live sound, I've seen VERY experienced announcers turn to silly 
putty with 100 msec.  Musicians start having issues with tempo with 
delays much more than 30-40 msec, which is why stage monitors have to be 
so bloody loud!

A common real world example is a "star" singing the Anthem at home 
plate, with an acoustic delay of 120-150 msec through the sound system 
to the singer's ears.  The solution is simple -- we give the singer 
undelayed sound from his/her mic into headphones or a big monitor 
speaker directly in front of them.

I don't know of any studies relating to delays and our ability to send CW.

73, Jim K9YC