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Frequency Deterioration through Air

post #1 of 13
Thread Starter 
So, based on my limited knowledge, I would guess that Lows deteriorate more in a room. For Photons, Energy and Frequency are directly proportional, so I would like think the same for sound waves. This could be a false assumption.

I ask this question because I just read on Innerfidelity that totally flat speakers in a room will sound Warm. I would think they would be bright. So, can anyone explain this to me? Thanks!
post #2 of 13
I don't understand your question. What do you mean by deteriorate?

As for flat speakers, that should be the design goal. Some people prefer more bass and less treble, but that's what EQ is for. And those people probably have no acoustic treatment, so any higher frequency harshness is more likely due to room reflections.

--Ethan
post #3 of 13
Thread Starter 
What I mean is that over a space, I thought bass would be less prominent because it has less energy and therefore would run out of energy quicker when going through the air molecules.
post #4 of 13

There are many different things at play here.

 

1) Attenuation of sound in air due to viscous, thermal and rotational loss mechanisms. This of course varies with temperature, humidity, pressure.

Attenuation increases with frequency. At 20°C, 40% humidity, 101.325 kPa:

1 kHz loss is about 0.005 dB/m,

20 kHz loss is about 0.578 dB/m

 

2) Directivity and dispersion. Tweeter have much narrower dispersion characteristics. Low frequencies will be radiated even backwards.

 

3) Room acoustics. There are reflections, resonances (room modes), room gain, boundary reinforcement ...

post #5 of 13
Thread Starter 
So essentially low frequencies seem louder than high frequencies if they are created at equal intensity from a distance?
post #6 of 13

If you play music very loud a half mile away and listen, odds are most of what you hear will be the bass. But in a room, the acoustics of the room itself are the limiting factor, not whether the sound waves don't travel distances well.

 

The reason that bass sounds louder from a great distance has to do with the directionality of higher frequencies. Bass tends to disperse better. However if you could create a horn speaker the size of a Mac truck, it would likely shoot out balanced sound for a very far distance!


Edited by bigshot - 11/3/13 at 11:40am
post #7 of 13
Quote:
Originally Posted by DutchGFX View Post

So essentially low frequencies seem louder than high frequencies if they are created at equal intensity from a distance?

 

They don't just seem louder but they are louder because low frequencies are attenuated less. But as bigshot wrote, and see the numbers posted above, you probably won't notice the effect unless you're many meters away from the source.

 

 

Room acoustics cause a much bigger difference. Place a speaker a few meters away from each wall on a stand and compare that to placing it in the corner of the room on the floor.


Edited by xnor - 11/3/13 at 12:25pm
post #8 of 13
Quote:
Originally Posted by xnor View Post
 

 

They don't just seem louder but they are louder because low frequencies are attenuated less. But as bigshot wrote, and see the numbers posted above, you probably won't notice the effect unless you're many meters away from the source.

 

 

Room acoustics cause a much bigger difference.

 

 

Quote:
Originally Posted by xnor View Post
 

There are many different things at play here.

 

1) Attenuation of sound in air due to viscous, thermal and rotational loss mechanisms. This of course varies with temperature, humidity, pressure.

Attenuation increases with frequency. At 20°C, 40% humidity, 101.325 kPa:

1 kHz loss is about 0.005 dB/m,

20 kHz loss is about 0.578 dB/m

 

2) Directivity and dispersion. Tweeter have much narrower dispersion characteristics. Low frequencies will be radiated even backwards.

 

3) Room acoustics. There are reflections, resonances (room modes), room gain, boundary reinforcement ...

Man you guys are always soo on point! *claps hand* and I mean that without any sarcasim. Seriosuly guys... I'm always impressed :O

 

that said LISTEN to these men... they KNOW WHAT THEY are talking about 

post #9 of 13

Go tell them that in the cables forum and see what they say!

post #10 of 13
Quote:
Originally Posted by bigshot View Post
 

Go tell them that in the cables forum and see what they say!

... I AM a fan of CABLES... PLACEABO FOR THE WIN ehm

 

:3 

post #11 of 13
Quote:
Originally Posted by bigshot View Post
 

If you play music very loud a half mile away and listen, odds are most of what you hear will be the bass. But in a room, the acoustics of the room itself are the limiting factor, not whether the sound waves don't travel distances well.

 

The reason that bass sounds louder from a great distance has to do with the directionality of higher frequencies. Bass tends to disperse better. However if you could create a horn speaker the size of a Mac truck, it would likely shoot out balanced sound for a very far distance!

No matter what speaker you design, the high frequencies will tend to be attenuated much more quickly than the low frequencies - this is due to the dissipation of energy into the air. As you said, this doesn't really make any difference in any reasonable-size room, but if you were standing a mile away from a very loud speaker, chances are you will only really hear the bass no matter what design you used (unless you intentionally overemphasized the treble the speaker was putting out to make up for the increased attenuation)

post #12 of 13
Quote:
Originally Posted by cjl View Post
 

No matter what speaker you design, the high frequencies will tend to be attenuated much more quickly than the low frequencies - this is due to the dissipation of energy into the air.

 

In a room, besides the narrower dispersion, it's usually due to absorption coefficients being higher at high frequencies. In other words, high frequencies will not be reflected as well as low frequencies from everything in the room and its walls.

post #13 of 13
Thread Starter 
Thanks guys, you hit the nail on the head, greatly appreciated!!!
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