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DPRG: BOUNCE dprglist@dprg.org: Non-member submission from [Gabe Velez <gvelez@richmond.infi.net>]

Subject: DPRG: BOUNCE dprglist@dprg.org: Non-member submission from [Gabe Velez <gvelez@richmond.infi.net>]
From: Jim Brown jimbrown at airmail.net
Date: Sun Jan 4 00:22:18 CST 1998

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>Subject: BOUNCE dprglist at dprg.org:    Non-member submission from [Gabe
Velez <gvelez at richmond.infi.net>]   
>
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>Date: Sat, 03 Jan 1998 17:38:40 -0500
>From: Gabe Velez <gvelez at richmond.infi.net>
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>To: Kevin Ross <kevinro at nwlink.com>
>CC: dprglist at dprg.org, rcb5 at msn.com
>Subject: Re: Fw: DPRG: Re: Audio
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>Kevin Ross wrote:
>
>> Nonsense. Lots of animals have extremely directional hearing, such as
>> Bats,
>> Horses, Bears, etc. When they detect a sound, they refocus their
>> parabolic
>> aperatures (ie ear lobes) in the direction of the suspected sound. It
>> allows
>> them to focus their processing attention on a particular direction for
>> more
>> detailed processing.
>>
>
>    Ah, but notice what you yourself said, "the parabolic shape of the
>ear lobes". The canal and ear mechanism itself is not cardioid.
>
>> The human ear is much more complex than a single entrance for sound.
>> The ear
>> lobe functions as a signal attenuation device as well as a directional
>>
>> finder. Our brains have been trained over time to detect the
>> differences
>> between a noise from in front vs behind. A person who loses an ear
>> lobe has
>> an extremely difficult time determining direction of sound with
>> respect to
>> front/back. The lobe causes a predictable change to the sound pattern
>> by
>> creating variations in the sound that are detected by the brain.
>> Extremely
>> cool, but way beyond this groups practical ability to duplicate.
>
>    This is only because we have eyes and hair. Tests done using
>headphones (eliminating acoustic dampening of hair, ears, etc.) or a
>blindfold (eliminating whether the person can see if  it is actually in
>front of him or not) show that a person cannot detect whether a sound of
>an object or noise is from behind.  But I did not do the tests. Acoustic
>engineers, psychoacousticians, et al, have. But I just read about it. I
>just tried it on myself to prove it to only myself.
>
>> >From a practical standpoint for creating a robot, a cardioid pattern
>> microphone is a great place to start. Your initial plan is seeking
>> maximum
>> sound levels on both channels. To determine the direction, you want to
>> have
>> maximum sound levels that are in phase with each other (ie start at
>> the same
>> time). I would use the starting edge of a sound wave, and time the
>> difference between the two.
>
>    Sure. Or make parabolic dishes for the micropone to focus on like a
>real animal. But as far as acoustic pressure, a microphones sensitivity
>to a sound, especially if the microphone is on one side of the robot,
>where the robots "head" is the barrier *like ours* or most other
>animals, does the job of making the "ear" directional, since its
>amplitude will always be greatest with the source directly in front of
>it.
>
>    As a matter of fact, the afore mentioned animals have higher
>frequency hearing ability. Higher frequencies are more directioal in
>themselves! Making for a cardioid pattern almost unnecessary. But if the
>mikes are out in the open with no barrier between them, then they should
>work fine.
>
>> If you get good success with this, you might be able to try a more
>> extensive
>> set of experiments.
>
>    As far as phase detection, well, the brain makes judgements on that.
>Its a psychoacoustic thing. And if you spend a couple of years and
>millions of lines of code to program a digital "intelligence" to do what
>the brain does, well, great! But then you will have a true voice
>recognition device! Cool!
>
>Cheers!
>
>Gabe
>
>
>
>
>
>
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