Friday, 28 February 2025

Hi-Fi Lessons (2): Useful Numbers

You will wind up learning a bunch of numbers by heart:

The sensitivity of your speakers in dB / m at 1 watt 
The diameter of your speakers' woofer and tweeter 
Twice the power = 3dB volume increase 
10 times the power = 10dB increase = "twice as loud"

30dB = what you think is silence - but actually isn't 
40dB = when no-one is talking on a new train 
50dB = it's not quite loud enough 
60-70dB = about the loudness of a normal voice. Or my acoustic guitar. 
80dB = the volume audio reviewers say they listen at - until their partners yell "TURN THAT DOWN" 95dB = the volume of the taped announcements on London Underground trains

343 m/s = speed of sound (roughly) at sea level 
Frequency = 343 / wavelength in metres; wavelength in metres = 343 / frequency;

27.5 Hz = frequency of lowest note on the piano, and known to music (outside stunt instruments) 
41 Hz = lowest note on double bass 
261 Hz = middle C - literally the middle of the piano keyboard, and the note between the treble and bass clefs in the Grand Clef 
440 Hz = note the oboe plays for everyone else to tune to, otherwise known as "A440" 
4,186 Hz = frequency of highest note on the piano, and known to music (outside stunt instruments)

No comments:

Post a Comment