this post was submitted on 22 Oct 2023
360 points (97.4% liked)
Technology
59039 readers
3203 users here now
This is a most excellent place for technology news and articles.
Our Rules
- Follow the lemmy.world rules.
- Only tech related content.
- Be excellent to each another!
- Mod approved content bots can post up to 10 articles per day.
- Threads asking for personal tech support may be deleted.
- Politics threads may be removed.
- No memes allowed as posts, OK to post as comments.
- Only approved bots from the list below, to ask if your bot can be added please contact us.
- Check for duplicates before posting, duplicates may be removed
Approved Bots
founded 1 year ago
MODERATORS
you are viewing a single comment's thread
view the rest of the comments
view the rest of the comments
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.
Trust this guy, when it comes to the small d he knows everything about it.
Oops, thanks for the correction!
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.
i love you
Yes. Industrial grade ultrasonic sensors are harmful to your health. They can be used, for example, to measure the water level in a tank. If you need to enter a place like that, you should physically disconnect the sensor first. You might not hear much of the noise, but you may feel it in your teeth or some other places.
Weren't there some huge high power sonars that could melt people to goo?
Yep, and hurt whales from the pressure.
Oh, so not all bad then