| Author |
Message |
yoyo
Guest
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 Posted:
Fri Dec 03, 2004 6:19 am Post subject:
Tone Cancellation ??/ Way over my head |
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This may not be the best place to ask, but!!
Currently I'm working on replacing siren speakers and sirens on a fleet
of police cars. They are very interested in 200watt speakers and
sirens. Most emergency equipment is 100 watt sirens with one 100 watt
speaker.
The system I'm looking at is a 200 watt siren that will drive two 100
watt speakers. In this particular case the speaker I have chosen is
actually one unit with two neodymium drivers sitting on top of each other.
My question is I have heard of certain tones that tend to cancel one
another when sounded at the same time, resulting in nothing or close to
it.
Does anyone here know range of such tones? and do I need to be
concerend with that? The audible frequency range of the siren unit is
300Hz-3000Hz. Also exactly what would the actual result be in two
speakers sounding the exact same tone??? louder? deeper? more punch?
Thanks Jonathan
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Jim
Guest
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| Posted:
Fri Dec 03, 2004 6:19 am Post subject:
Re: Tone Cancellation ??/ Way over my head |
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"yoyo" <yoyo@yahoo.com> wrote in message
news:xOQrd.14380$E84.11674@fe79.usenetserver.com...
| Quote: | This may not be the best place to ask, but!!
Currently I'm working on replacing siren speakers and sirens on a fleet
of police cars. They are very interested in 200watt speakers and
sirens. Most emergency equipment is 100 watt sirens with one 100 watt
speaker.
The system I'm looking at is a 200 watt siren that will drive two 100
watt speakers. In this particular case the speaker I have chosen is
actually one unit with two neodymium drivers sitting on top of each other.
My question is I have heard of certain tones that tend to cancel one
another when sounded at the same time, resulting in nothing or close to
it.
Does anyone here know range of such tones? and do I need to be
concerend with that? The audible frequency range of the siren unit is
300Hz-3000Hz. Also exactly what would the actual result be in two
speakers sounding the exact same tone??? louder? deeper? more punch?
Thanks Jonathan
|
I would imagine, if they are directly next to each other, you will get a 3db
increase. As for tone cancellation, i dont think that would happen,
unless you inadvertadly reversed the polarity of one of the horns, then they
would pretty much cancel each other out.
Jim |
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Phildo
Guest
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| Posted:
Sat Dec 04, 2004 12:09 am Post subject:
Re: Tone Cancellation ??/ Way over my head |
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"yoyo" <yoyo@yahoo.com> wrote in message
news:xOQrd.14380$E84.11674@fe79.usenetserver.com...
| Quote: | My question is I have heard of certain tones that tend to cancel one
another when sounded at the same time, resulting in nothing or close to
it.
|
Sounds like one of the drivers is out of phase. Try reversing the polarity
of one of them.
| Quote: | Does anyone here know range of such tones? and do I need to be concerend
with that? The audible frequency range of the siren unit is 300Hz-3000Hz.
Also exactly what would the actual result be in two speakers sounding the
exact same tone??? louder? deeper? more punch?
|
You should get a 3db increase when both speakers are producing the same
sound if they are close enough to couple.
You might also want to try adding short bursts of white noise in with the
siren signal. One of the studies I did at university was on how to improve
emergency sirens and adding noise like that enabled people to discern the
direction the emergency vehicle was coming from much more easily.
Phildo |
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TimPerry
Guest
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| Posted:
Sat Dec 04, 2004 6:21 am Post subject:
Re: Tone Cancellation ??/ Way over my head |
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"yoyo" <yoyo@yahoo.com> wrote in message
news:xOQrd.14380$E84.11674@fe79.usenetserver.com...
| Quote: | This may not be the best place to ask, but!!
Currently I'm working on replacing siren speakers and sirens on a fleet
of police cars. They are very interested in 200watt speakers and
sirens. Most emergency equipment is 100 watt sirens with one 100 watt
speaker.
The system I'm looking at is a 200 watt siren that will drive two 100
watt speakers. In this particular case the speaker I have chosen is
actually one unit with two neodymium drivers sitting on top of each other.
My question is I have heard of certain tones that tend to cancel one
another when sounded at the same time, resulting in nothing or close to
it.
Does anyone here know range of such tones? and do I need to be
concerend with that? The audible frequency range of the siren unit is
300Hz-3000Hz. Also exactly what would the actual result be in two
speakers sounding the exact same tone??? louder? deeper? more punch?
Thanks Jonathan
|
this is nothing new, Federal Light and Sign, Whelen and others have done
this for years. the 2 drivers are screwed into a "Y" or "T" section of pipe
then a reflex horn is fitted onto the assembly.
im an told by the local service guys that the current state of OSHA
requirements do not allow placment of the sirens in the light bar due to
potential hearing damage. |
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