Rules of thumb for music and audio

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Not sure whether anyone's posted this before, but there's a very good article here by John Siau of Benchmark Media Systems: Rules of Thumb for Music and Audio.  It's long-ish but an easy and entertaining read.

For those preferring instant gratification, here's a summary of the rules:

Rule 1: Light and electrical signals travel about 1 foot in 1 ns.
Rule 2: Sound travels about 1 foot in 1 ms.
Rule 3: Light travels 1 million times faster than sound.
Rule 4: A 2-foot open pipe resonates at 262 Hz which is middle C. (“2, 262, middle C”)
Rule 5: An octave change in pitch requires a 2:1 change in size. Bigger is lower.
Rule 6: A piano has a range that exceeds 7 octaves.
Rule 7: 0 dB SPL is the threshold of normal hearing.
Rule 8: 130 dB SPL is about the highest peak loudness that we can tolerate.
Rule 9: A 1 dB change in loudness is a just noticeable difference (JND).
Rule 10: A 3 dB increase in loudness requires a 2X increase in power.
Rule 11: A 6 dB increase in loudness requires a 4X increase in power which is a 2X increase in voltage.
Rule 12: A 10 dB increase in loudness requires a 10X increase in power.
Rule 13: In a home environment, the SPL at the listening position is about the same as the 1m response of the speaker in an anechoic chamber.
Rule 14: Every bit in a digital system adds 6 dB to the signal to noise ratio (SNR) of the digital channel.
Rule 15: The bandwidth of a digital system is 1/2 of the sample rate.

Enjoy!