A familiar question

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Strungout_dave

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Am learning what Db is i came upto the point of
DB= 10*Log(X/Y) after that i was reading about the correlation of Intensity and pressure in sound.Where they stated with a formula of p2/P where P is the pressure and P in italics is for Air impedance.. then they latter on went on to explain it with a example that we had derived early on in the artice. (The lowest sound pressure level that a human can detect is .000000000001 W/m2 so with the formula I= Pa2/P (With the P- room temprature of 400) they said .000000000001= .00002/400 which i didnt understand and and 1w/m2 = 20/400! how did they derive to this.. please forgive me if this a very simple question.. am new to audio and have a very little knowledge in Physics ;-).

Any help would be nice!
 
Good thing is - you don't need to be a physicist do learn audio!
 
Dave,

As Bear said, you don't really need any of that to be a recording engineer. Here's what really matters:

dB is a relative concept. A change of 1 dB is about as small as most people can hear. A change of 6 dB sounds about twice as loud (or half as loud).

When you see dB used as an absolute level, like someone says "you should mix with the volume at about 85 dB" the dB is still relative, but in this case to a reference level of total silence.

Likewise, dB is used for input and output levels, like pro gear at +4 dBm and consumer gear at -10 dBV. Those too are relative. dBm means relative to one milliwatt, and dBV is relative to one volt.

--Ethan
 
Ah!! i see what u mean.. But not yet :-p

Thanx a lot ethan for taking ur time to responding to my post. so Db is just a refrence level.. But what does it mean if my signal is at 0 db and why does my master level goes beyond 0 when my tracks are at unity or even below it?
 
On an analog circuit 0db is usually the cleanest possible signal. Better circuits can handle higher levels before distortion and that is usually called 'headroom'. Different gear responds differently at different levels and with some stuff you push and with others you go easy. With digital audio 0db is the highest possible level before distortion and digital distortion is harsh and ugly.
 
Re: Re: A familiar question

Ethan Winer said:
A change of 6 dB sounds about twice as loud (or half as loud).
Click to expand...
That goes against everything I've ever read and seen published.

My references define an increase of +10dB is being perceived as 2x the apparent loudness. This is defined as an increase of 10 PHONS (+10dB-SPL).

[ edit ]

damn typos...

:D
 
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There's seem to be some confusion on the 10db/6db thing and loudness. I don't know the exact answer but when you double the distance from the source the sound is perceived to drop by 6db. When you increase the sound by 10db you get a perceived doubling in volume.

Those two principles would seem to contradict each other and is probably part of the confusion.
 

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Re: Ah!! i see what u mean.. But not yet :-p

Dave,

> so Db is just a refrence level <

Exactly. And 0 could be anything. 0 on a cassette recorder or open reel tape deck meter is usually 12 dB below 3% distortion. But it could be anything, and pro tape decks even have adjustments so you can make 0 be whatever you want. As they say, "It's all relative."

--Ethan
 
BG,

> That goes against everything I've ever read and seen published. <

Okay, you could be right. I was just guessing. Of course, what sounds "about twice as loud" can vary from moment to moment and person to person. It probably also depends on the frequencies present.

--Ethan
 
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