this post was submitted on 22 Oct 2023
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Can't hear but still cause damage?
I didn’t know the answer to this so I looked it up - yes. Over 120 Db can cause damage even if it’s ultrasonic and you can’t hear it. Apparently at 155Db the heat created by the sound wave can be dangerous as well.
Just a small note, it's written dB, small "d", big "B".
"B" is the unit symbol for bel and "d" is the symbol for the SI prefix deci, a tenth.
In that case can we use just B. MB, etc.
Oh yes, sure you can, 140 dB is 0.000014 MB. The confusing thing is just that the non-SI unit byte also uses the symbol "B" and uses the SI prefix "M" quite often.
Sometimes when I calculate optical power levels I actually use B in between. For example:
How much signal is 88 optical channels at 1.6 dBm of power each?
0 dBm = 1 mW by definition
1.6 dB = 0.16 B = log10 ( x ) --> x = 10 ^ 0.16 = 1.45
So 1.6 dBm is 1.45 * 1 mW = 1.45 mW
Then 88 channels is 88 * 1.45 mW = 127.60 mW = 127.60 * 1 mW
log10(127.60) = 2.11 B = 21.1 dB
So 127.20 mW is 21.1 dBm, just below the output specification of our amplifier, good, nothing should melt.