On 14/04/2023 04:18 pm, Norman Wells wrote:

> On 14/04/2023 13:39, NY wrote:
>
>> I used to be able to hear the 15625 Hz line frequency of 625-line TV.
>> Not so it was intrusive but I was aware of it, especially in a TV shop
>> where there were a lot of TVs close together. The 10125 Hz of 405-line
>> TV was very noticeable, though it was rare to find those TVs en-masse.
>>
>> I don't think I could ever hear the 19 kHz pilot tone of stereo FM
>> radio. I could distinguish stereo FM from mono by the increased hiss,
>> but I wasn't aware of a single tone.
>
> Makes you wonder what ill effects it may have had, completely oblivious
> to us, on domestic pets, like dogs.  Kids who could hear high
> frequencies intensely disliked the short-lived Mosquito deterrent as I
> recall, so dogs must have been able to hear them.

When playing the Sgt Pepper CD, my son (then aged about 9) asked:
"What's that funny noise?".

He meant the "run-out groove" tone (originally after "A Day In the Life"
on Side 2) for dogs.

I certainly couldn't hear it.

> It's also a theory of mine that dogs especially were aware of the
> flickering of CRT televisions, which they never seemed interested in,
> however good we regarded the picture.  But there are numerous examples
> now of dogs, and cats, watching LED TVs and reacting to their content as
> if it were real, such as this:

> https://www.youtube.com/shorts/sjvcR4jNKcE
>
> I wonder if that's ever been established scientifically?

Dunno. My cat used to react to (CRT) images of birds in flight, pawing
at the screen.