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Re: Nature recording 101

Subject: Re: Nature recording 101
From: Walter Knapp <>
Date: Thu, 24 Feb 2005 14:02:51 -0500
From: Marty Michener <>

> RE: the sound - wind tradeoff
> 
> This discussion has gotten to its usual point, here, as it seems to every 
> year, with Walt sounding the most like he understands the actual physics, 
> and everybody verbally dancing around the causal aspects at various 
> distances. (ok, I'm a snob about saying the same thing over and over! But 
> it needs to be resaid.)

You are being too kind, I know the physics only on a general level. I do 
have the advantage that in a former part of my life I worked at earning 
money as a expert on computer modeling and also measuring air pollution. 
As part of that you have to understand airflow pretty well. At least 
well enough to produce a computer model that could come close to what 
you measured. And know where to place your intake to the sensors. Some 
of that knowledge I've transferred to recording.

One of my other hobbies is kite flying. It can teach you a whole lot 
about wind flow too. When I lived in Seattle, some of the kite club 
members specialized in flying kites inside. Without walking around. 
There are air currents everywhere.

> Sound vs wind is all related to laminar vs. turbulent flow -- fluid 
> dynamics. I will make this short, and in outline form, in the interest of 
> time - yours and mine:
> 
> No turbulence, no wind noise! Turbulence is produced for a given rigid 
> structure above a critical velocity, which is why there is, for any setup, 
> a certain wind speed above which we give up and stop recording. If you want 
> a demo of this, try your water faucet: turn it on very slow and increase 
> the speed gradually - watch (and hear) the turbulent point.
> 
> A. Modifications of wind protection hardware to reduce wind noise (aka: YOU 
> COULD MAKE OR BUY):
> 
> Walt is exactly right - it is not the structure that reduces the noise, it 
> is the slower air.  To be specific - air flowing in straight layers 
> produces no noise and conducts sounds well.

As I've noted, with sensitive mics that have very low self noise, even 
what looks like laminar flow produces some noise as it strikes the mic. 
Even at very low wind speeds.

> B. Modification of human recording behavior to reduce wind noise (aka: YOU 
> SHOULD MAYBE TRY):
> 
> This is a whole category not even touched on (unless I missed something) 
> and is very important.  In fact I OWN NO WIND SCREENS - except what "came 
> with" my Sennheiser mics.  So what do I do?

Because of the nature of the survey work which dominated quite a bit of 
my recording I have not had to luxury of just coming back another time. 
I have to get the recording as it occurs. That lead me into wind 
protection. Once I had good wind protection I found how often my 
recordings were being compromised by even very light wind. So I use the 
protection often. But it's still true, the best recordings are usually 
done in no or very little wind. Unless, of course, you are trying to 
record the wind.

> 1. Get yourself as far away from other wind-related noise sources as 
> possible (see next point, C below).
> 
> 2. Get yourself in the lowest wind velocity area - behind a tree or car 
> even works.
> 
> 3. Orient your mic so the long axis is parallel to the wind - but you can 
> hear this for yourself and it becomes second nature.  Of course that may be 
> easier said than done, where you must point the mic AT the sound you want, 
> so it may mean moving to a different perspective on your subject, or 
> approaching from upwind or downwind direction as possible.
> 
> 4. Get low. The earth itself has a very slow layer of air next to it, where 
> the sound you want MAY be still recordable - this depends on each 
> situation, but it is always worth a try. Try it even without wind, some 
> sounds are louder and some quieter near the ground.
> 
> 5. For those subject to our preoccupying passion who like to set the mic on 
> a stand and leave it - a lot of this category goes unexplored -- another of 
> my twenty reasons I gave up on parabolas (which I used from 1956 until 
> recently) in favor of easily-walkable rigs.

These are all good methods in the situations where they can be used. But 
that's a small subset of all recording situations. I've used every one 
of them where they worked. And in some situations used several together. 
They are easier to use in wooded areas, try doing things like that out 
west where it's very open.

I should note that anything that protects you from wind is also probably 
a sound source from the wind as it produces some turbulence. The catch 
22 of hunkering down behind something.

I do find the Telinga a perfectly good walkable rig. I never use it on a 
tripod, unless it's the high one. In fact the high tripod is the only 
way I use a tripod at all, everything else is hand held. I have shotgun 
mics, and they do not substitute for parabolas, so I won't be putting 
the Telinga aside. Though, now that I have other good choices I'm no 
longer forcing it to work where it's not the best choice. In terms of 
wind protection, the Telinga is the easiest to protect.

As I noted, I've recently become aware of the different character of 
breeze I'm finding at the top of a 17' tripod. It's often easier to wind 
protect up there than at hand held height. I'm sure it has to do with a 
little less turbulence up there. Anyway, now that I've noticed it, I'll 
be watching what I can do with that.

> C. Wind noises that cannot be reduced:
> There is a long list, a few:
> Hissing and banging among plant parts. Dried oak leaves are the worst I 
> found.  Solution - get far away from them.
> Flag pole rope banging and flag snapping. (yccht. I just threw that in ;^0 )
> Make your own list . .

I contend that the worst is pine trees, at least for me. It takes almost 
no wind for them to be hissing away, loudly. Often the ground level wind 
is very slight, but the tops of the pines are up in slightly stronger 
stuff and can really drown out your recording.

Walt






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