Re: OT: Microphone experts mainling-list
Re: OT: Microphone experts mainling-list
- Subject: Re: OT: Microphone experts mainling-list
- From: Dave Hunt <email@hidden>
- Date: Tue, 30 Jan 2018 10:57:21 +0000
Hi Mahboud,
Binaural microphones can be very easy to build. There are a number of small
electret omni-directional, capsules around. Go for one with a good frequency
range and low noise, possibly described as "instrumentation" capsules.
They need a small voltage, but the 1.5V supplied by most portable digital
recorders is adequate for basic needs. This can provide a very portable and
discrete recording system. Obviously you don't try monitoring what you are
recording with headphones while using your own head as the dummy.
I have buit a pair of these into a very cheap set of headphones with open back
grills. You can just remove the drivers and solder the cable to the mic
capsules, which can be glued in place. Plug the result into the mic input of
the recorder. Done carefully these can sound very good, better than many more
expensive stereo microphones sold to go with these portable recorders.
The capsules end up pointing into the ear canal, but if they are not allowed to
enter the ear canal this is not a huge problem.
I have also tried using ear buds or headphones which use a hook over the ear.
These are a bit trickier, as you probably need to have the capsules pointing
outwards.
It is very difficult to adequately shield such microphones from wind, though
you could try making fake fur ear muffs if you don't mind it looking silly.
These recordings can then be imported into a computer. As Richard says, a
spectral display (or two, one for each channel) will be more useful than
looking at the waveforms. Documentation of where the source sound is coming
from, and possibly alignment with another recording of a microphone pointing at
the source may also be revealing, though of course that will contain less
information about the reflected sound in the environment. Two spaced omnis well
away from the dummy head may be better, and reveal the influence of the ear,
head and torso on the binaural recording.
The HOFA 4U Goniometer & Korrelator may be useful though it is not available
for iOS.
Ciao,
Dave
On 25 Jan 2018, at 09:18, Mahboud Zabetian <email@hidden> wrote:
> Thank you very much!
>
>
>> On Jan 25, 2018, at 12:47 AM, Richard Dobson <email@hidden> wrote:
>>
>> That's a very cool idea ... but also very difficult. The overall topic is
>> generally referred to as "localisation". You are describing "dummy head
>> recording". Spectrum analysis will be an important tool, though in some
>> cases inspecting the waveform may show how phase differences between the
>> ears contribute to localisation. This "inter-aural difference" is an
>> important element. It is known, for example, that localisation depends not
>> only on distance, but also on pitch - low frequencies are virtually
>> impossible to localise as the phase is not sufficiently different between
>> the ears. Which is why we may need 5 speakers, in just the right positions,
>> to hear music in "surround", but just one sub-woofer, which can be placed
>> just about anywhere.
>>
>> The best place to ask about this is probably the sursound list, where there
>> is plenty of expertise on spatial audio, microphones, dummy heads, such
>> things as HRTFs, the role of the pinnae in sensing source direction, etc.
>> There are opinions on whether a dumy head is enough, or whether you need a
>> dummy torso as well, as it is thought we pick up subtle reflections from the
>> torso as another spatial clue.
>>
>> https://mail.music.vt.edu/mailman/listinfo/sursound
>>
>> Richard Dobson
>>
>>
>> On 24/01/2018 22:21, Mahboud Zabetian wrote:
>>> Hi. I know this isn't the right list, so if you please know of one, send
>>> me a link please.
>>> My daughter's doing a project for school. She wants to install two mono
>>> mics on a mannequin head, and record left and right from each so that she
>>> can do some experiments with how human ears hear sounds spatially. She'll
>>> be combining the two mics into one mic jack and then use AudioEngine on iOS
>>> to record two separate files of audio simultaneously. She will then play
>>> with the audio files on a Mac to make or break her hypotheses.
>>> I'm in charge of microphone procurement. I wanted something relatively
>>> flat that could be installed in an over-the-head headphone, so that she
>>> could easily go from mannequin to a person's head. I wanted it to work
>>> well without an amp, since that would just complicate things for her (I
>>> can't help her more than to pay for the microphone or show her the
>>> AudioEngine sample code).
>>> Any tips would be appreciated. (Good audio visualization tools would be
>>> great too. She may be getting some help from a university professor who
>>> suggested studying the waves on an oscilloscope. These days there must be
>>> plenty of tools on the Mac or iOS, no?)
>>> Thank you.
>>> mahboud
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