We're all familiar with the noisy, "squelchy"-sounding audio that seems to characterize voice communications between astronauts and mission control during NASA space missions. Most of us don't give it a second thought, but a poster over at diyAudio wonders why does the audio have to be so bad?
He has a point. Given today's technology - or even 1970's or 80's technology - and the relatively low requirements for reproducing good quality audio, what's the excuse for the poor audio quality heard on low-earth orbit operations like the International Space Station and shuttle missions?
The question has fueled speculation by other forum participants who have chimed in with a variety of possible explanations - some serious and some, well, not so much:
- Old technology - e.g., NASA's still using 1960's germanium transistors
- Bandwidth limitations
- The audio is intentionally degraded - if it sounded too good, no one would believe it was from space
- Is it SSB?
- Something to do with a reduced pressure atmosphere?
- It's analog
- High ambient noise requires throat mics (or noise-cancellation mics)
- Electrically noisy environment
- Failure to use proper audiophile interconnect cables
The conclusion so far seems to be that the low audio quality probably results from a combination of old (1980's) technology and a greater focus on improving video quality. One poster also claimed that the sound was probably consistent with the mic used - "a Crown GLM that has been ruggedized and mounted to a box with the PTT [push to talk] and preamp circuitry inside" - along with heavy compression, companding and band-limiting signal processing.
The thread also includes a link to technical info on the Apollo radio as well as a Boeing page that describes the communications and tracking system on the International Space Station.
Comments, questions or suggestions? Post your comments below or email me at firstname.lastname@example.org.