Measuring loudness in reviews

[goeiecool9999]

In this video Linus mentions the fan goes up to "70+ decibels". I'm not a physicist by any means, but shouldn't decibel measurements come with a measurement distance?
Decibel is simply a measurement of pressure difference. Since the pressure goes down the farther you're away from a sound source you can't really deduce any useful information from a number like 70 dB.
After some google foo I found this page: http://www.noisehelp.com/decibel-scale.html where under the section "Measuring Sound Levels" it's mentioned that "For a reported sound level value to be most useful, it is necessary to specify the conditions under which the reading was taken, especially the distance from the source." leading me to believe my suspicions are correct.

Any thoughts?

[ARikozuM]

You're absolutely correct. I haven't watched the video, but decibels are logarithmic, so the farther you go, the lower the actual sensation of pressure that you'll feel. 

 

Edit: Without knowing the distance and ambient controls, we have no way of knowing what the pressure difference is between the two.

[vanished]

You're right they have to be associated with a distance, but the trick is, for comparison purposes, they measure everything at the same distance, so as long as you're not comparing to anyone else (just different LTT videos), it's not important.

[yathis]

4 hours ago, Ryan_Vickers said:

You're right they have to be associated with a distance, but the trick is, for comparison purposes, they measure everything at the same distance, so as long as you're not comparing to anyone else (just different LTT videos), it's not important.

Yeah but they also need a sound isolation room.

[vanished]

Just now, yathis said:

Yeah but they also need a sound isolation room.

Yeah that wouldn't hurt.  The quieter the product is (closer to ambient levels) the less reliable and meaningful the measurement becomes

[yathis]

1 minute ago, Ryan_Vickers said:

Yeah that wouldn't hurt.  The quieter the product is (closer to ambient levels) the less reliable and meaningful the measurement becomes

It wouldnt really take up too much space really.

Not sure how much that sound isolation foam would cost.

L-man could probably get sponsored and get it for free.

He did for that server room fabric.

[LogicalDrm]

Usually measuring distance is 30cm. Or it should be that. 70db from 30cm would break some ears. Linus has habit of going for insane numbers instead of actual numbers.

[bobhays]

On 6/14/2017 at 4:12 PM, ARikozuM said:

You're absolutely correct. I haven't watched the video, but decibels are logarithmic, so the farther you go, the lower the actual sensation of pressure that you'll feel. 

 

Edit: Without knowing the distance and ambient controls, we have no way of knowing what the pressure difference is between the two.

You're right that the farther you are the lower the decibels, but that has nothing to do with being logarithmic.

[ARikozuM]

Just now, bobhays said:

You're right that the farther you are the lower the decibels, but that has nothing to do with being logarithmic.

I probably worded it poorly and can't even remember what I was trying to say to attempt fixing it. 

[yathis]

Whats the saying go, 1dB is double the loudness

[LogicalDrm]

14 hours ago, ARikozuM said:

I probably worded it poorly and can't even remember what I was trying to say to attempt fixing it. 

You probably wanted to include fact of desibel scale being  logarithmic. Which is something people used to temp/price/performance measuring ofter forget.