The first recording was done yesterday with amazing 3D results. It certainly feels as being there. The sound quality is great too as expected from world class large diaphragm moving coil transducers connected to Pleiades filters. The high frequency detail of outdoor sounds was thrilling and a joy to hear as well as the fabulous smooth midrange and natural bass. Unnatural but interesting was that the sound seemed to be coming many times from behind. (At the back of the recording subject there was a large room with its reverberation, more investigation is needed).
The microphones were held by hands.
Each microphone was gently touching each ear.
On the first recording the omnidirectional microphones were pointing upwards.
On the second recording the microphones were pointing downwards, perhaps with a decrease in 3D quality, more experiments are needed.
The experiments took place on the balcony, the open balcony door situated behind the back of the recording subject. So they were performed outdoors but at the back the room was somewhat reverberant being a large space.
A Pleiades filter of 82mH was connected across the output of each mic to compensate the bass increase to brain.
There wasn't the slightest hint of hiss, the Seenheiser being world class microphones and the SONY cassette recorder with its input transformers too. A TDK CDing type II cassette was used. The SONY TC-D5 PRO II had its recording level potentiometer at 10, the VU meters showed severe under modulation since the sound was ambience,. No Dolby reduction was used. Birds sounded real.
The Pleiades filters did an excellent job of making the bass balance sound correct to the listener's mind.
The setup: (sound source outdoors ambience)
Right ear - MD21 HN - Pleiades 82mH -
- SONY TCD5 PRO II - Sennheuset HD 580
Left ear - MD21 HN - Pleiades 85mH -
Why?
Could this be considered a recording of the sound coming out of our ears? The pressure soundfield is influenced by the existence of the ears, their shape and the tympani reflection which is a manifestation of what is happening further inside.
In fact what is being recorded is the interference pattern of the ambient sound and its reflection from the ear.
Like a Hologram, see Hugo Zucarrelli, Mike King Holophonics binaural recording patent.
So why not using the headphones themselves as microphones?
Recording drums with the Sennheiser HD 580 headphones gave very promising results (see an older euroelectron post on the references). There was a problem with exaggerated bass. If the right Pleiades filter (6dB per octave) cannot be found to compensate this, then 12db per octave filters can be used, EMI RS106A types, inductor in parallel, capacitor in series and then inductor in parallel.
At first it seems silly. At which direction should the mic point to?
How about towards the ear?
How about in ear dynamic (moving coil in a magnetic field) headphones as they are, with no modification, used as microphones?
Just a step up transformer will be needed. It can be made with a Magnetec 073 core with few primary turns to reduce excessive bass and enough secondary turns to make the impedance of ordinary 8ohm headphones to 300ohms as mics ready to record. And then using the same or similar headphones for playback.
Summary: At first it might seem very strange recording pointing the microphone towards one's ears or using the headphones themselves connected as microphones. But in fact one records the interfierence pattern of the soundfield been reflected by the ear. Like in holography.
Aklowkedgment to Hliana for bringing up so often the phenomena of interference and superposition.
References:
Hugo Zuccarelli patents
Sound and Hearing - Life encyclopedia - S.S. Stevens - p.99 - Ch.5 The Two-eared Man
(A fascinating account of none other than S.S.Stevens director of the Laboratory of Psycho-Physics at Harvard University visiting none other than Dr. Harvey Fletcher, director of research at Bell Telephone Laboratories for the demonstration of live binaural experiments using dummy lifelike figure named Oscar, with microphones next to his ears.
Other posts on euroelectron, on using HD580 headphones as binaural microphones
http://euroelectron.blogspot.gr/2016/09/how-did-sennheiser-hd-580-sounded-as-3d.html
Also other posts on using pairs of omnidirectional dynamics such as D130, MD21 held next to the ears.
P.S.(Could an editor of the excellent wikipedia take into account of the first 2 references on the excellent Binaural Recording article?)
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