Scott Shepard wrote:
>If you define sound as periodic rarefications and compressions of a gas
>medium, then this is not a sound. What has been detected, over all that
>distance and time, is electromagnetic radiation. By the same token, the
>signals traveling through your audio cables are not sound. They are
>electrical signals ANALOGOUS to a sound event. Takes a transducer such
>as a microphone or speaker to convert between the two.
>It's easy to confuse them, I remember some confusion about it coming up
>in my electroacoustics class in EE school. The point of the story, I
>think, is that the frequency of the electromagnetic signal detected was
>such that, if it were a sound, it would be the pitch indicated. Not
>very precise scientific journalism, calling it a sound.
You misunderstand the original evidence. No super-low-frequency
electromagnetic signal has been detected. What has been seen
(visually) is waves of compression and rarification in interstellar
gas. From the photographs the speed and wavelength has been
calculated. Compression waves in gas are properly described as sound.