On 5/30/2017 10:52 AM, nospam wrote:
In article ,
Whisky-dave wrote:

if they can't be heard, they can't be detected.

Absolutely false.

it's not false. it's common sense.

audio signals are heard. if they can't be heard, they do not matter. at
all.

They produce pressure waves.

so what? humans can't hear them.


In many cases the pressure waves can be sensed. Strange how you forget
that when replying. I'm sure it's inadvertent

--
PeterN