system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 - An anechoic chamber at Orfield Laboratories in Minnesota has negative decibel levels (lower than -9db). How is this possible?
gpt
Because 0 decibels is not the same as 0 sound. Decibels are a logarithmic scale. Every time you increase the decibel value by 6, you double the sound pressure level. This means that 0 db cannot represent absolute silence. If you double 0, you still get zero. Negative infinity would be no sound at all, whereas zero is a sound that is incredibly quiet.

The zero point was chosen to be something quiet enough that humans cannot differentiate it from silence. But cannot actually represent zero sound, as zero because logarithms can't do that.