Topic: dead rat home wind tunnel tests

[SmokinJoe]

Hey now,

I've been planning to make some dead rat windscreens, and being a overly analytical type person, I started to get really curious about the best type of fabric, and trade-offs between windproofness and loss of sonic properties.  My wife brought home a couple of different fabrics, and I have been trying to decide which one to use.  I decided to do some living room testing this evening, trying to be a little scientific about it.

Bottom line: The results are not surprising.  Basically I have to agree with what tribal knowledge has been saying all along.  Wind noise is a killer, and while you may loose some sonic goodness from dead rats, it's not a huge amount.

Setup:
- SP LSD2 Stereo Mic, set to Blumlein > UA-5 > H120
- A typical 2 foot square box fan (department store variety)
- Mic and fan about 5' apart.  Fan is blowing at the mic from the left.  Blumlein means the wind hits both caps at 45 degrees.
- home surround sound system, with 6 small speakers + a big subwoofer.
- Played the same familar tune (so everyone should know it what it is supposed to sound like.)  Didn't change an level settings between tests.

Test:
- recorded Track01 with no wind, no windscreen, just sound as a baseline
- Turned the 3 speed fan on to "low".  I'm guessing it creates a 10 mph breeze.
- recorded Track02 with wind, no windscreen at all, definite windnoise and clipping
- recorded Track03 with wind and the stock foam windscreen.  You can definitely hear the noise from the fan running,
  but no wind noise across the capsules (that I detect)
- recorded Track04 with wind and the stock foam windscreen + "dead poodle" fabric draped over the mic
  (not a finished screen yet, just fabric thrown over, hanging all around). I call the fabric "dead poodle" because it has short curly hairs.
  It has a relatively loose knit backing fabric.
- recorded Track05 with wind and stock foam windscreen + "dead bear" fabric draped over the mic.
  This has about 2" long fur (aka dead bear) and the tips were gently swaying in the breeze. The backing fabric on this was fairly tight, almost like burlap.

Results:
- With this amount of wind, the stock foam windscreen is adequate. I don't know how much wind it will take before you need the dead rats.
- It's hard to tell how much loss of highs there is... (the fan motor makes too much noise.)  I think there is probably a little more loss at each step,
  but it's not bad... certainly not "OMG, that sucks", which is actually what I was expecting.
- I think the answer is that if it seems windy at all, use the dead rats to be safe, and most people don't need to get too hung up about the loss of sonic qualities.

I think I'm going to go with long bear fur for the LSD2, and curly poodle fur for the Nak shotguns. and drag them to outdoor festivals.  If you see dead poodle fur on some long shotguns at a festival, it's probably me. 

A zip file with 5 flac files and more audacity screenshots is available here (12.3mb)
http://www.cs.usm.maine.edu/~bouchard/LSD2_wind_test.zip

Below are audacity shots (a) calm conditions, (b) with wind noise generating spikes, and (c) with a stock windscreen blocking the wind.

Joe

[shukenja]

great stuff i wish i had patience to do teste like that as well. my wife would probably think i went really crazy, haha


anyway, what fabrics exactly did you used ? i might try to experiment with dead rats myself, and going to fabric shop asking for "you know, this fur " wouldnt be a best option i guess...


did you had any problems mounting these rats on SP ? they're not shotgun-shapes mics like AKG or RODE, and the standard windscreen is very curvy rather than cigar-shaped, isnt i t?

[wheresjerry]

Nice work Joe!  Now, question, did you, or your wife sew these up?  Maybe we could use a set of your dead rats for our own heads!  Now that would be a look out in the field.  Your wife might think your nuts conducting your test, but then again, my wife thinks we're all nuts!  If Annie can't make me a set, you up for doing some business?

[stevetoney]

Hey Joe:

Good job.  I asked a couple days ago about this, so it's definitely timely info for me.  I think I'll either make some or buy some from here.

BTW Joe...where you goin' with that gun in your hand?

[guysonic]

Did conclusive tests on windscreen materials for use with my company's mics many years ago.   

Used pink noise into stereo speaker system and mic on a stand connected up to memory type spectrum analyzer.  This analyzer allowed recording/comparing by showing ONLY difference of the mic spectrum with/without different windscreen materials in front of the mic. 

Found ALL synthetic fabric/foam materials significantly distorted the spectrum, but nearly pure cotton fabric was transparent 20-20K Hz.

My version of cotton fabric windscreens for DSM stereo-surround mic sets is shown at www.sonicstudios.com/access.htm#whb

[SmokinJoe]

To answer some of the questions...

I did the tests while the wife was out for the evening.  She already knows I'm nuts, but it's still easier than dealing with the obligitory sarcasm. 

I expect if you go to a decent fabric store (I think Joanne's Fabric may be a nationwide chain?) and ask for "fake fur" (a) they won't really look at you strangely, and (b) they won't have 20 different kinds... maybe a couple different textures, in a few different colors and you pick the one you find least annoying.  I suspect being overwhelmed with selection isn't really a big problem.  My dead rats will be black, but I did get some outrageous blue/green fur I was thinking about using for a J-Disc.

We haven't actually sewn them up yet.  My wife will probably do the sewing, but just for the record, I COULD do it.... I used to make a lot of those Frostline kits... camping equipment etc, when I was boy scout age.  If I tried to sew them, my wife would be "Oh, you're doing that all wrong! Here let me do it!".  So I don't even try.  After 21 years of marriage, I have learned my place.  My job is to go the bars and tape shows, hers is to stay home and be in charge of sewing.  I can live with that. 

The cotton fabric for the sonic DSM.... sounds interesting, but it sounds like it is used to allow you to get "the sounds of the wind"?  I don't want the sounds of the wind, I want the sounds of the musician.  Or are you saying, it cut out all the wind, so you could hear the leaves rustling, etc.? I wonder how this works for different mics... I would think LDs would be a lot different than binaurals.

Joe

[Brian Skalinder]

Found ALL synthetic fabric/foam materials significantly distorted the spectrum, but nearly pure cotton fabric was transparent 20-20K Hz.

How did the pure cotton fabric compare to the synthetic/foam materials for windscreens' primary purpose:  preventing wind from causing rumble and noise?  Tough to tell from the pics on your page, but in the WHB/N is there a cage + screen that provides an open air cavity in which the caps reside?

[guysonic]

Found ALL synthetic fabric/foam materials significantly distorted the spectrum, but nearly pure cotton fabric was transparent 20-20K Hz.

How did the pure cotton fabric compare to the synthetic/foam materials for windscreens' primary purpose:  preventing wind from causing rumble and noise?  Tough to tell from the pics on your page, but in the WHB/N is there a cage + screen that provides an open air cavity in which the caps reside?

Found the cotton fabric (even doubled) was transparent to spectrum, and eliminated mic wind blast 'effects' noise.  However, unlike non-transparent to audio synthetic foam/fabric type windscreens that mostly eliminate all wind sounds, cotton fabric allows some natural wind (not mic noise effects) sounds when winds are strong or gusty.

[momule]

I gave up on the faux fur sometime ago and picked up a yard of High quality fleece and was happy to find that they blocked as much wind as the Fur and did not dull the highs nearly as much if at all.  I just make fleece jackets that slide over the stock screens.

I have tested these at Both Red Rocks and wakarusa (windy outdoor festival) with vey nice results. 

[alpine85]

if pure cotton is the most transparent, then why wouldn't a pair of cotton socks held on with a rubber band work?

for extra reinforcement, you could stuff the socks with cotton balls.

i think i'm going to try this - wish i would've read this before Langerado!!

[Javier Cinakowski]

if pure cotton is the most transparent, then why wouldn't a pair of cotton socks held on with a rubber band work?

for extra reinforcement, you could stuff the socks with cotton balls.

i think i'm going to try this - wish i would've read this before Langerado!!

tapinfool here on taperssection uses socks, even indoors.  I have to admit, they work very well.  I used Rycote windjammers for my lavs and his socks actually worked better.  About the same amount of wind attenuation and better high frequency responce...

One year at a local festival some Schoeps guy was making fun of tapinfool becasue he was using a mixer powered by a car battery, a pair of Oktava's and some old socks for wind protection.  The Schopes guy brought his fancy headphones over to listen from the mixer.  They guy was jaw dropped when he reallized that tapinfool was pulling a fantastic recording.  Don't judge a book by its cover! 

[Gutbucket]

I've found synthetic shirts (polyester blend) to be much more transparent to high frequencies than cotton ones.  This from raw ear analysis only, swishing fingers together, shaking shakers, jingling keys etc.  Maybe a thinner, wider weave cotton would be different.  I've put together some ghetto rycote-a-likes last week and have used woman's nylon hose material on them figuring it works fine for studio pop-shields but have wondered if I can find something better.. and about making some furry versions.  What material is on the real Rycotes? I'm sure they've analyzed that stuff to death.

[digifish_music]

Joe, thanks a lot for this, excellent work. One thing about your test, I have used fans before myself to test windscreens, and quickly noticed that they lack the plosive effects real wind has, that is the turbulence and slugs of air impacting the mics.

I have done quite a bit of field recording at the beach, in fairly gusty wind, so the value of the faux fur then is it provides some shock absorption effects when the gust hits the mic. In those situations the mechanical thump is transmitted straight through the foam covers, but faux fur keeps on performing. Foam balls do work well in fairly laminar flow conditions tho.

Perhaps, your test Mk II should include and oscillating fan so you can test the onset of a gust?



digifish



 

[guysonic]

I've found synthetic shirts (polyester blend) to be much more transparent to high frequencies than cotton ones.  This from raw ear analysis only, swishing fingers together, shaking shakers, jingling keys etc.  Maybe a thinner, wider weave cotton would be different.  I've put together some ghetto rycote-a-likes last week and have used woman's nylon hose material on them figuring it works fine for studio pop-shields but have wondered if I can find something better.. and about making some furry versions.  What material is on the real Rycotes? I'm sure they've analyzed that stuff to death.

I wouldn't be calling this material "transparent."

By looking at the spectrum change through synthetic (like polyester) noticed a definite 'hype' of mid-high frequencies that might sound like a brightening, but it is artificial and likely the effect pf some kind of active acoustic modulation/resonating of the synthetic fibers. 

However, even if not natural or an artificial effect, I've found many here actually prefer hyped microphone sound.

[John Willett]

There is a lot more in all this than people think.

Type of "hair", thickness of the strands, length of the strands, having a mixture of lengths, backing material, etc., etc..

Rycote actually have the material for their Windjammers made specially for them and a lot of research was done to get the material right to maximise the wind protection and minimise the attenuation of the high frequencies.