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Discussion Starter · #1 ·
Got into Prius "quietness" discussion. Need some help on dB.

Discussion generated desire for some 'rules of thumb' regarding dB. eg one person suggested every 3 dB increase equals doubling the volume of sound. :?:

Is that reasonably accurate ? That would say that 63dB is twice as loud as 60dB, and 66dB is twice as loud as 63dB. Can that be right ?

Accurate or not, can some of you help me, in laymen terminology, with some rules of thumb for relative dB numbers. ?

no logarithms (sp?), formulas, math, :roll: please. I appreciate & understand the relationship is not linear.

for example, what is the difference in loudness btwn 65dB & 70dB; btwn 65dB & 75dB... etc.

thanks !!
 

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Sounds right

I can give you the whole math, but, then, you could find it on the web also (through google.com).

Yes, every 3db increase "sounds" like double the volume to your ears. "db" is the value of log operation.
 

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3dB corresponds to a doubling of power (the number of watts). But, this doesn't mean it sounds like it is twice as loud. In laboratory tests, people can just barely discern a difference of 1dB (a 25% increase in power). In normal situations the just noticable threshold (JNT) is around 3dB.

Hope this helps,
Shawn
 

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Discussion Starter · #4 ·
Re: Sounds right

ceric said:
I can give you the whole math, but, then, you could find it on the web also (through google.com).

Yes, every 3db increase "sounds" like double the volume to your ears. "db" is the value of log operation.
thanks, yes, I googled dB before I posted this question, and waded through a bunch of stuff that tried to convert me to a sound engineer :lol: but did not find good "rules of thumb" in laymen's terminology, so I appreciate the help.

Any other interpretations, assists would be welcome.
 

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The antique chart in my sound level meter has this information:
db effect
20 whisper
30 soft music
65 conversayion
90 start of unsafe sounds
etc.

Prius at speed is about 70 db
 

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TucsonPrius said:
3dB corresponds to a doubling of power (the number of watts). But, this doesn't mean it sounds like it is twice as loud. In laboratory tests, people can just barely discern a difference of 1dB (a 25% increase in power). In normal situations the just noticable threshold (JNT) is around 3dB.

Hope this helps,
Shawn
It would seem to me this site disagrees with you.
http://hyperphysics.phy-astr.gsu.edu/hb ... nd/db.html

The JND (just noticeable difference) (is this different from "JNT"!?) is 1db instead of 3db.
3db is 2X the power of sound wave.
10db increase in sound makes human ears perceive as 2X louder.
 

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Doesn't disagree at all. I said, in laboratory tests people can discern a 1dB difference. In the real world, it's closer to 3dB, which is doubling the power.

Thanks,
Shawn
 

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Are there cheap meters to test the noise level in the car? I am getting some sound proofing installed in one of our Prius and want to test both to see what the difference is.
 

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Discussion Starter · #10 ·
Tadashi said:
Are there cheap meters to test the noise level in the car? I am getting some sound proofing installed in one of our Prius and want to test both to see what the difference is.
I bought an excellent digital sound meter at Radio Shack...about $50. Portable, uses a 9v battery. I've used it in the car a number of times to ck out dB of different road surfaces, windows open/closed etc.
 

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GreyMud said:
I had looked at it, but thought that most of the sound is coming through the windows, so it wouldn't be worth the effort.
Have you tried closing the windows? :twisted:
 

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Discussion Starter · #13 ·
mgaelli said:
GreyMud said:
I had looked at it, but thought that most of the sound is coming through the windows, so it wouldn't be worth the effort.
Have you tried closing the windows? :twisted:
WOW... I LOVE this site. And now I can hear the radio. :?
 
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