Topic: Phase Shifting

[blu666z]

Can someone explain phase shifting to me?  I may be using the wrong term, but I am listening to DMB 07.02.97 @ Red Rocks and sounds like the sound source moves around occasionally.

-Kevin

[Jason R]

Great question!!  Happens on outdoor tapes esp. big festivals.  I'm not sure if that is the right term but I have my ideas.  I will stay tuned for a wise one's answer....Is this from the wind moving the PA speakers when they are hanging fro the stage rigging

[danmorgan]

It's caused by the wind "shifting" soundwaves in the air.  Has a bigger effect on the higher frequencies and seems to cause losses in detail, namely in something like a cymbal crashing.  Listening through headphones you can notice it significantly...sounds like the sounds are moving between channels.

My best explaination, if some one has something more scientific, please do post....
 :twocents:

RR is a venue that would definately produce this more commonly.

[Craig T]

same sound waves out of phase will cancel each other out.  results in loss of certain frequencies - mostly affects the highs.  caused by improper mic configurations (too much or too little spacing) and by environmental factors such as wind and air temp (both can interfere with the speed of the sound wave).

[leegeddy]

It's caused by the wind "shifting" soundwaves in the air.  Has a bigger effect on the higher frequencies and seems to cause losses in detail, namely in something like a cymbal crashing.  Listening through headphones you can notice it significantly...sounds like the sounds are moving between channels.

My best explaination, if some one has something more scientific, please do post....
 :twocents:

RR is a venue that would definately produce this more commonly.

.....my physics memories aren't that great, but i believe it has something to do with sound waves traveling though a moving fluid (air) affecting the higher frequencies which are more directional than low freq.  maybe it's somehow related to Doppler's effect??

if the PAs are moving, you will hear the same pitch but with phase shift, you actually hear a difference in pitch.

sorry i couldn't explain it better.

marc

[blu666z]

Thanks guys.  Any info was more than I had to being with.  +Ts all around.

-Kevin

[plucks]

Red Rocks tapes can sound real bad since it is a venue that is at the base of the foothills which often have strong winds.  When there is no wind, the results are amazing though!  
There are some omni sources that sound amazing and do not have any major phase shifting from the wind.  Omni's at RR are generally not a good idea though since the seating area is sloped rather steeply for an outdoor venue.

Phase shifting is really a difference in the sound waves arriving at different, or unexpected, times, in this case from the wind.  Professionally, phasing is looked at how equally the sounds come from or play out of a system.

This is about Phase Shifting: http://www.espace-cubase.org/anglais/page.php?page=level1pp1

Here is a link on digital phasing, which isn't on par, but the phase idea is right on: http://www.earlevel.com/Digital%20Audio/Phase.html

Unfortunately, our hobby is generally overlooked for examples of the differences in time in which the sound waves arrive.  

Phil

[1st set only]

why dont we hear this while we are in the venu? why is it only on tape?
is there a optimal config for windy situations?

[Tim]

why dont we hear this while we are in the venu? why is it only on tape?
is there a optimal config for windy situations?

I hear it at shows all the time (outdoor of course).. it can be really distracting.

[Chuck]

why dont we hear this while we are in the venu? why is it only on tape?
is there a optimal config for windy situations?

I hear it at shows all the time (outdoor of course).. it can be really distracting.

Oh yeah you can hear it at the concert.  
It is very noticable on cymbals.

[plucks]

you can definitely hear it at RedRocks while at the show

[chase]

i remember hearing somewhere that this can be corrected in wavelab somehow, but it has to be done on the fly.  anyone know how this is done?

[cpclark]

im not sure if this a correctable problem, i know for certain that phase shifting is due to the wind moving direction frequencie's around and in some respects can be minimized by a nice and beefy windscreen, this is why at almost any outdoor festival, tapers are running large windscreens to eliminate or severely minize phase shifting, now rodrocks can be overpowering, and sometimes phase shifting cannot be minized. also there has to be a pretty significant wind to be audible to the human, i.e. why alot of redrocks tapes have these problems

[danmorgan]

im not sure if this a correctable problem, i know for certain that phase shifting is due to the wind moving direction frequencie's around and in some respects can be minimized by a nice and beefy windscreen, this is why at almost any outdoor festival, tapers are running large windscreens to eliminate or severely minize phase shifting, now rodrocks can be overpowering, and sometimes phase shifting cannot be minized. also there has to be a pretty significant wind to be audible to the human, i.e. why alot of redrocks tapes have these problems

The only thing windscreens will limit is rumbling noise from the wind.  Phase shifting will still be present regardless of windscreen size when using directional mics....

[Tim]

i remember hearing somewhere that this can be corrected in wavelab somehow, but it has to be done on the fly.  anyone know how this is done?

someone on here was convinced that they could effect phase by adjusting volume in wavelab or some such nonsense. Jason B and I spent an afternoon and explained how this was not possible.

so no, you are pretty much stuck with it and windscreens won't help at all with phase shifting.