Re: Sound source?


"Freg" <nospam@xxxxxxxxxx> wrote in message news:45a2d0c9$0$97264$892e7fe2@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
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| "Andro" <Headmaster@xxxxxxxxxxxxxxxxxx> wrote in message
| news:rvtoh.18172$MO2.9940@xxxxxxxxxxxxxxxxxxxxxxxxxxxx
|
| "Freg" <nospam@xxxxxxxxxx> wrote in message
| news:45a2569d$0$97264$892e7fe2@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
||
|| "Andro" <Headmaster@xxxxxxxxxxxxxxxxxx> wrote in message
|| news:Ovsoh.18096$MO2.1269@xxxxxxxxxxxxxxxxxxxxxxxxxxxx
||
|| <pispaspos@xxxxxxxxx> wrote in message
|| news:1168261849.243432.288880@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
||| Good day!
|||
||| I have a question regarding sound sources. If I have a horn speaker
||| with a high directivity and I stand 500 ft away from it, can I consider
||| it as a point source?
||
|| Insofar as there any point sources, sure.
||
||| I am assuming a scenario where two listeners are standing opposite from
||| each other and each being 500 ft away from the speaker. The speaker is
||| pointed to one of the listeners.
|||
||| I am curious about what the sound levels will be and if modeling the
||| sound source as a point source for propagation purposes will work.
|||
||| Thanks!
|| You'd have to assume no reflections (echoes) and note that
|| the speaker WILL be heard directly behind it. I doubt
|| the horn is 500 ft long or made of lead.
||
|| unless there is a phase cancellation
|
|
|
| It is kinda hard to have a phase cancellation without another
| sound source.
|
|
| think about it,
| as the sound from the front has to wrap around to the back, from the left
| and from the right, there is a null in the back of the speaker, phase
| cancellation.
| there is some freeware on the internet that can plot this for you

It takes time for the sound from the front to reach the back.
Any phase cancellation depends in the frequency and path
length.
There are courses in schools and colleges that can teach
you this, but the best teacher of all is experience. I installed a
horn behind the seat of a Harrier flight simulator to simulate
the double whine (two concentric shafts) of a Rolls Royce
Pegasus as the pilot hears it with his helmet on, hitting 112 dB
in the cockpit.
That could be heard 100 feet away down the corridor through
three closed doors to the annoyance of other employees
and I was placed on late shift to do the testing.
The sound signal itself originated from a special sound card
built before Soundblaster existed and was controlled by
software running the simulated engine on an Interdata 8/32,
just before the outbreak of the Falklands war.
http://www.link-miles.co.uk/images/picright.jpg
http://www.fas.org/man/dod-101/sys/ac/harrier-swa.jpg
http://www.jetpower.co.uk/cr201_1.htm
YOU think about it, Mr. Nospam Internet Freeware.


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