> I don't know of any studies relating to delays and our ability to
> send CW.
Empirically the issue starts to become noticeable when the delay is
more than an element (dit/dah) and certainly becomes critical when
the delay is a substantial part of a letter. Just like the "soloist"
and the National Anthem, the solution is to provide undelayed sidetone
from the keyer rather than an off air monitor or RF derived sidetone.
BTW, another place acoustic/DSP delays have become an issue is with
live TV news. In the old days we used off-air analog signals or
analog cell-phones for "IFB" (interruptable fold back) but with the
advent of digital cellular systems and digital broadcasting, the delays
are well in excess of the "magical" 150 - 200 ms threshold. For TV
applications, the solution is to provide "mix minus" - that is the
program feed *without* the reporter's own voice - so the reporter
can interact normally with other participants.
73,
... Joe, W4TV
On 9/1/2012 11:57 PM, Jim Brown wrote:
> 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
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