Topic: HRTF Dummy Head

[china_rider]

Hey now... Was looking at the dummy head in the pictures section and it reminded me I wanted to set up something better than I already have for HRTF recordings not on my head.  This is more of a side project and I can't really afford to go out and purchase a ready made one.

So I would be mounting DSM-6SMs.  The last head I made I had bought a Styrofoam head from a wig shop.  After that I cut the leg off a pantyhose put it over the head and then stuffed a pretty thick padding of cotton between the two all around.  It was easy to put the stand mount in the neck of the head but since it was Styrofoam it did not last very long.  I had good results but it did not really sound as realistic as when I actually wore the mics.  I think the cotton absorbed too much but that is just a guess.  Without the cotton I thought the Styrofoam would reflect to much.

Anyone know of a good guide for making a quality one of these?

Stay Kind,
Dana

[boojum]

You have identified that your own is the best.  A dummy head is good the more it resembles a human head.  Some sport wigs.  Having the mics in the ear canals is an improvement.  I would think the styrofoam would work pretty well as "skin."  Poach from sites on the Internet which have made them.  That is how I made my Jecklin disc.  And if I make an HRTF head I will be doing it the same way.

FWIW - Google returned ten pages on HRTF dummy.

Cheers

[china_rider]

You have identified that your own is the best.  A dummy head is good the more it resembles a human head.  Some sport wigs.  Having the mics in the ear canals is an improvement.  I would think the styrofoam would work pretty well as "skin."  Poach from sites on the Internet which have made them.  That is how I made my Jecklin disc.  And if I make an HRTF head I will be doing it the same way.

FWIW - Google returned ten pages on HRTF dummy.

Cheers

My own head might be the best.... But sometimes a guy just has to go pee during the show. :-}

As for the binoural in ear it is suggested that the Sonic Studio HRTF is better over a wider series of playback systems (headphones, stereo, mono, surround, etc) where binaural shines with headphones but can have some issues when listening on other playback models.  In basic comparisons iv'e found this to be true.  I also like how the HRTF is easily translated in to dolby surround.

I actually have an idea of what I want to do, but before I go all out I wanted to get some opinions here.  Basically what I found (google searches) was to buy the Styrofoam head and make a mold out of it then use ballistics gel to make the head.  While creating the mold, insert the stand mount and you are good to go.  I'm guessing I can do this for about $125 but am not exactly sure how much gel you need to make a head so it could be more or less.

Just thought I would see if anyone here had a good tried and true method for doing this.

Stay Kind,
Dana

[guysonic]

HRTF is based on size, shape AND ABSORBTION characteristics of WATER BASED HUMAN HEAD.  Our heads ABSORBS (not reflects) most ALL AUDIO FREQUENCIES.   

In other words, water based flesh absorbs sound, reflecting almost nothing off its surface.  My Sonic Studios designed GUY and LiteGUY HRTF baffle remain the only (100% acoustically correct) available today. 
See:www.sonicstudios.com/guypage.htm and most practical www.sonicstudios.com/liteguy.htm


Guy/LiteGUY baffles are not easy or cheap to make so maybe only practical for the serious amateur or professional needing true HRTF performance, but these cost many thousands less than (far less effective/accurate) well-known synthetic dummy head alternatives.

So using cotton for absorption qualities was a step in the right direction, but has far too little absorption to work even OK over the very active and hard Styrofoam material.   MOST all synthetic materials do not absorb audio frequencies effectively, and in fact, while some foams/rubbers do absorb some portions of the audio band, they are quite ACTIVE in making significant changes to the frequency amplitude/phase OF THE ACOUSTIC PRESSURE signatures needed for HRTF baffle fidelity.  In other words, they COLOR the sound (making EFFECTS) in noticeable manner to be a liability to making consistently good sounding recordings.

The only really cheap and good sounding HRTF (type) baffle for those on a budget remains cotton fabric covered ~head shape/size hard-stuffed (fiberfill/cotton batten/wool) pillow or even a cotton-cord-bound bath towel or similar constructed baffle works more like what's needed for consistent good sounding results.  Baffles made of these fibers can be ~2/3's head size and still work well.  Best to have mic spacing/baffle width ~7-8" even if head height is shortened to as much as 50% for having a compact easier to transport baffle.


In summary, all those other materials do not absorb enough, and are active in altering the sound in audible ways not HRTF.  No matter how good those other (synthetic material) dummy head baffles may look to the eye, they are producing significant anomalies in HRTF acoustic terms.

[boojum]

^^^ Thanks for the info.

[guysonic]

You have identified that your own is the best.  A dummy head is good the more it resembles a human head.  Some sport wigs. Having the mics in the ear canals is an improvement.  I would think the styrofoam would work pretty well as "skin."  Poach from sites on the Internet which have made them.  That is how I made my Jecklin disc.  And if I make an HRTF head I will be doing it the same way.

FWIW - Google returned ten pages on HRTF dummy.

Cheers

What you're describing here is true binaural. HRTF is not true binaural, in the sense that the mics are not within the baffle (head).
HRTF has the mics spaced at a heads width distance, with the mics pointing forward toward the sound source, and completely exposed. Whereas, true binaural has the mics within the head, capturing all the ambient information as its reflected inward, toward the eardrum/mic capsule.
Its a subtle difference, that is a major sound influence.

Much confusion is from not realizing there are many forms of HRTF recording based on the acoustic response of the human head.  In-ear-binaural is just one form of mic array using HRTF to shape the pickups response.  Outside, but very close to the ear-canal is another variation of binaural where the outer ear+head, but not the inside ear canal is used and has slightly different imaging characteristics/results.  

For example, Sennheiser's hotly debated binaural patent involved pickups placed outside, but within a specific distance from the ear canal opening.  

My own HRTF patented approach uses ONLY the HRTF of the head (sans any ear effects) with 2 pickups placed ~two-finger-width distance forward of ear's edge to achieve universal stereo-surround imaging reproducible through all kinds of 2 or more headphone/speaker/surround multichannel playback systems.  Four channel DSM mic using HRTF effect, but places two additional rear-channel pickups on locations behind and again at some distance from both ears.

All these various methods are HRTF related mic array approaches, and produce recordings with different playback characteristics.

[Brian Skalinder]

My own HRTF previously patented (now expired) approach

Fixed that for you. 

[SparkE!]

My own HRTF previously patented (now expired) approach

Fixed that for you. 

Ever the helpful moderator!  You crack me up sometimes.  +T

[guysonic]

My own HRTF previously patented (now expired) approach

Fixed that for you. 

Thanks for bringing up a good point about patents.  While a patent has exclusivity time limit on infringement, it remains forever to protect a working inventor using the patent established now as PRIOR ART forever. 

This means no one else can legally re-claim patented prior art already established as now their own, and later demanding fees or shutting out the inventor from continuing an established business.  This has occurred to inventors not granted patents, and who were later shut down by someone else being granted exclusive rights used to legally demand license fees, or even eliminate market established competition.

So even though having reached exclusive term time-limit, efforts to be granted a methodology patent continues to be of great value to Sonic Studios, insuring no one else can legally demand fees, or in any way keep me from continuing the refinement and manufacture of DSM stereo-surround microphones.

Patents, they keep working and working providing inventors with legal rights and protection from ruthless business interference; don't leave home without one!

 

[SparkE!]

My own HRTF previously patented (now expired) approach

Fixed that for you. 

This has occurred to inventors not granted patents, and who were later shut down by someone else being granted exclusive rights used to legally demand license fees, or even eliminate market established competition.
 

I assume you are speaking from experience since your patent essentially shut down the sales of similar gear that taper hobbyists were making for other tapers?

[guysonic]

My own HRTF previously patented (now expired) approach

Fixed that for you. 

This has occurred to inventors not granted patents, and who were later shut down by someone else being granted exclusive rights used to legally demand license fees, or even eliminate market established competition.
 

I assume you are speaking from experience since your patent essentially shut down the sales of similar gear that taper hobbyists were making for other tapers?

NO existing products or patents where challenged by my patent being granted as it was not based on over-riding or modifying prior art claims to cause infringement on my or their part.  Prior art was referenced for the patent process as is required for purposes to show what existed, that a thorough search of past granted patents was likely done correctly, and how my claims took a different tact to produce unique results not previously experienced.

Sennheiser was one of several very large companies producing a HRTF based mic array products.  Theirs was patented and used unique claims and array design.  Their decision to end production seems more based on economics from lack of sufficient sales than anything else.  No one has found any other plausible reason for them not to continue making their brand of headworn mic.

Tapers can make anything they like for themselves even though using patented intellectual property and methods.  It's only if starting a business based on somebody else's patented intellectual property that licensing is required to continue within the patent's exclusivity time period. 

As history has shown, many large companies have shown to ignore patented intellectual property of others, and later have been sued (even after a patent has timed-out losing exclusivity) for very large sums for the period of infringement activity.

[kenndelbridge]

I'm working on a similar project, but am using a filled halloween skull and 2 silicone ears, with AKG C417 lav mics inserted in the ear canal. Initial tests are sounding very good, although the skull is creeping some people out. I will probably add a wig to improve sound absorption, although right now, Harry the Holophonic Head's exterior texture is a soft latex.

[china_rider]

That is pretty creepy.  I tried pouring the ballistics gel this weekend.  With the advice above I was going to pack the outside with cotton like I did with the Styrofoam.  Never working with the gel before I did not realize how heavy it was once it finally set.  I would guess the head is around 20 lbs.  No way I'm lugging that around or putting it on top of a stand.  Also, in talking to the friend that helped me the gel can start to come apart in hot weather and this would be used in south west most of the time so not the best solution.  I think we will probably end up going camping next weekend and use it for target practice.   

[kenndelbridge]

An explanation about the ears - they're acupunture student practice ears, for acupunturists to perfect their technique on a human ear without the risk of hurting someone. So, they're 100% anatomically correct and the texture is very life-like. They weren't expensive, although they were a little oversized, unless you happen to be a hulky great German wrestler. What they didn't sell was a pull apart head with the ears, which would have been perfect...

http://www.3bscientific.com/shop/u.k./models/2_acupuncture_ears_n15,p_3_8_304_0_405.html

[guysonic]

That is pretty creepy.

 --clip--------

 I think we will probably end up going camping next weekend and use it for target practice.   

October 31st is not too far off, maybe keep it around a little longer recording the night's ghoulish happenings at your front door?

[jacobmyers]

I'm working on a similar project, but am using a filled halloween skull and 2 silicone ears, with AKG C417 lav mics inserted in the ear canal. Initial tests are sounding very good, although the skull is creeping some people out. I will probably add a wig to improve sound absorption, although right now, Harry the Holophonic Head's exterior texture is a soft latex.

Harry is awesome! All "he" needs now is a 6" tall, 2" thick foam-rubber "Mohawk" in the color of your choice (like a pseudo-Jecklin disc) and "he'll" be all set for rawk-recording mayhem. <sark> The silicone ears aren't creepy at all. </sark> But putting a "real" wig on it would be totally creepy.

[digifish_music]

HRTF is based on size, shape AND ABSORBTION characteristics of WATER BASED HUMAN HEAD.  Our heads ABSORBS (not reflects) most ALL AUDIO FREQUENCIES.   

Yours is a head-shaped baffle. I am sure it works very nicely. One advantage of a reflective head-shape is that you can gain some boundary-effect if you place the capsules in the right place...but who am I to speak authoritatively, I will happily use a cardboard box



http://www.freesound.org/samplesViewSingle.php?id=57668

But more seriously, strapping some nice omni-mics either side of a 6" block of wood does work very, very well...that's what I was simulating above.

http://www.trackseventeen.com/soundscapes/mic_rigs.html



I have to get around to making use of this...hard resin head, about 1/2" thick



digifish

[digifish_music]

Thanks for bringing up a good point about patents.  While a patent has exclusivity time limit on infringement, it remains forever to protect a working inventor using the patent established now as PRIOR ART forever. 

This means no one else can legally re-claim patented prior art already established as now their own, and later demanding fees or shutting out the inventor from continuing an established business.   

It certainly does not protect them from competition once the patent expires, so they have 25 years exclusivity to make hay while the sun shines, then it's a free-for all. Hopefully the inventor has moved onto new technology/IP by then, but in the case of simple and important inventions the expiration of the patent brings an end to their profitability as the clones flood the market.

In practice most patents can be worked around by variations on the theme. It has always interested me that you can't patent a recipe (for food) and yet the restaurant/food industry is doing very well thank you    

digifish

   

[digifish_music]

As history has shown, many large companies have shown to ignore patented intellectual property of others, and later have been sued (even after a patent has timed-out losing exclusivity) for very large sums for the period of infringement activity.

...and many have gotten away with it. As you have one or more patents you will know the huge legal costs that can be involved, particularly if you are challenged/challenge others. The challenge process also often involves the case being heard by non-experts and which way the challenge goes can depend (as usual) entirely on the whim of those involved rather than a thorough understanding of the issues contested. There are also very different rules in the EU and US patent systems (and a challenge may require you to act in a foreign country using foreign patent attorneys). It can get messy and take 10 years to sort out. Patent games are not for the poor or faint hearted

digifish

[IanR]

I reckon a large, tight-leaved cabbage, like a red or a white cabbage, would make a pretty decent HRTF baffle. Weighs a few pounds, mostly water, roundish . . . like a head. 

Just bung it in one of those little black stuffsacks you can get from camping shops if you don't want people laughing at it.

[SparkE!]

I reckon a large, tight-leaved cabbage, like a red or a white cabbage, would make a pretty decent HRTF baffle. Weighs a few pounds, mostly water, roundish . . . like a head. 

Just bung it in one of those little black stuffsacks you can get from camping shops if you don't want people laughing at it.

That is an excellent idea!  I've used a bowling ball before and it worked great, but I was very worried about the stand getting knocked over.  That would really hurt if it fell on your foot!  A cabbage wouldn't be so bad.

[IanR]

You could turn it into coleslaw for revenge 

[Gutbucket]

Mmm cabbage.  Delicious idea.

A guy at Magfest a few weeks back had a Zoom recorder sweat-banded to his forehead - I should have snapped a photo.