| Author |
Message |
E. Hill
Guest
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 Posted:
Wed Dec 15, 2004 5:30 am Post subject:
Re: Ambient temperature |
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| Quote: | That compensation is applied to the delay settings, because sound velocity
changes with the density of the medium it propagates in and the density of
the air decreases as the temperature rises.
Diffraction and ducting also happens with sound, and inversion layers over
an audience can make high frequency paths bend and propagate in unexpected
ways. There isn't much a temperature probe can do about that because its a
function of temperature gradient.
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That is a very real issue with the heating and air conditioning systems
functioning...
I remember being in a room with a 14' ceiling... When the heater was turned
on in the winter, the room sounded like the ceiling was lower.
Eric
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Phil Allison
Guest
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| Posted:
Wed Dec 15, 2004 6:25 am Post subject:
Re: Ambient temperature |
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"Alex Axolotl"
| Quote: |
That compensation is applied to the delay settings, because sound velocity
changes with the density of the medium it propagates in and the density of
the air decreases as the temperature rises.
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** The velocity of sound depends only on the air temperature - for a room
at 0C the speed is 331 m/S and for 25C it is 346 m/S - a 4.5%
increase. This has no effect on the perceived sound quality since the speed
change affects all frequencies equally.
| Quote: | Diffraction and ducting also happens with sound, and inversion layers over
an audience can make high frequency paths bend and propagate in unexpected
ways.
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** The gradual loss of high frequencies over a long path is partly due to
this.
............... Phil |
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Robert McTigue
Guest
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| Posted:
Wed Dec 15, 2004 6:35 am Post subject:
Re: Ambient temperature |
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| Quote: | Yes, although I'll bet the change in humidity was also a factor.
Humidly is a factor but its the air temp that will change it all. I have
a
great pick of the "highend air absorption" if you want me to email it to
you.
I'd very much like to see that Rob.
Cheers
Phildo
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Did you get the picture/graft scale? |
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Robert McTigue
Guest
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| Posted:
Wed Dec 15, 2004 6:35 am Post subject:
Re: Ambient temperature |
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| Quote: | ** Pure gobbledegook.
The speed of sound is the same for any frequency - so relative arrival
times at a listening point never alter.
Think it through.
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Phase shift can occur with temp. change is all I'm saying. If he put his FOH
off center and the room temp changed there would be a small bit of phase
shift and it could increase or decrease some of the low end response. It's
old information as it was published in 1947 by Dr. Harry Olson in his book
"Acoustical Engineering".
I like to set up subs in what's called "straight line" never exceeding 240
degrees (2/3 of cycle) for wide rooms and put them in a row (up to down
stage) 90 degrees(1/4 of cycle) apart then delayed for directivity control.
If FOH on in one of the cancel spots and the air temp changes say from a
cool 15C to a hot 37C you might here the change from the cool part of the
day. Its all in the book. |
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Phil Allison
Guest
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| Posted:
Wed Dec 15, 2004 6:36 am Post subject:
Re: Ambient temperature |
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"Robert McTigue"
| Quote: |
** The velocity of sound depends only on the air temperature - for a
room at 0C the speed is 331 m/S and for 25C it is 346 m/S - a 4.5%
increase. This has no effect on the perceived sound quality since the
speed change affects all frequencies equally.
True ... but if FOH is in the right spot (not dead center) as the temp
changes there is a bit of phase shift which could put him in a combfilter
change, depending on how the subs are set up.
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** Pure gobbledegook.
The speed of sound is the same for any frequency - so relative arrival
times at a listening point never alter.
Think it through.
.............. Phil |
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Robert McTigue
Guest
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| Posted:
Wed Dec 15, 2004 6:36 am Post subject:
Re: Ambient temperature |
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| Quote: | ** The velocity of sound depends only on the air temperature - for a
room
at 0C the speed is 331 m/S and for 25C it is 346 m/S - a 4.5%
increase. This has no effect on the perceived sound quality since the
speed
change affects all frequencies equally.
|
True ... but if FOH is in the right spot (not dead center) as the temp
changes there is a bit of phase shift which could put him in a combfilter
change, depending on how the subs are set up. |
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Phildo
Guest
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| Posted:
Wed Dec 15, 2004 6:25 pm Post subject:
Re: Ambient temperature |
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"Robert McTigue" <robertmctigue@comcast.net> wrote in message
news:mfKdnfXu9_lIKyLcRVn-1Q@comcast.com...
| Quote: | Did you get the picture/graft scale?
Yes thanks, interesting stuff. |
Phildo |
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