harry wrote:
On Sep 15, 11:49 pm, The Natural Philosopher
wrote:
Dave Plowman (News) wrote:
In article ,
tony sayer wrote:
I don't think that any of them go down that low in fact no audio
equipment I know of does, they tend to filter off below 20 Hz just
calling it wasted audio...
Except the equipment to measure turntable rumble?
There is no problem in the electronics: its the transducer that is the
problem

Not sure where standard microphone capsule stops..


So if it can' tbe measured then no-one knows thatit actually exists?
Sounds like urban myth to me. Invented to suit the NYMBYs?

Where in my post did I say it couldn't be measured harry?

It is not amenable to measuring on standard hand held noise meters, no.

That doesn't mean it cant be measured. As anyone who knows anything
about acoustics would know.

The world is littered with infrasound detectors, to monitor seismic
activity and nuclear explosions.

Unfortunately, they are not £150 hand held devices.


--
Ineptocracy

(in-ep-toc-ra-cy) €“ a system of government where the least capable to
lead are elected by the least capable of producing, and where the
members of society least likely to sustain themselves or succeed, are
rewarded with goods and services paid for by the confiscated wealth of a
diminishing number of producers.

Chris J Dixon wrote:
The Natural Philosopher wrote:

Dave Plowman (News) wrote:
In article ,
tony sayer wrote:
I don't think that any of them go down that low in fact no audio
equipment I know of does, they tend to filter off below 20 Hz just
calling it wasted audio...
Except the equipment to measure turntable rumble?

There is no problem in the electronics: its the transducer that is the
problem

Not sure where standard microphone capsule stops..

http://www.bksv.com/Products/handheld-instruments/sound-level-meters/sound-level-meters/type-2270.aspx?sortOrder=

3 Hz-20 kHz broadband linear frequency range


3 Hz-20 kHz broadband linear frequency range
16.6 - 140 dB *A-weighted* dynamic range with supplied microphone Type 4189

"A" weighting is USELESS for infrasound.

Chris


--
Ineptocracy

(in-ep-toc-ra-cy) €“ a system of government where the least capable to
lead are elected by the least capable of producing, and where the
members of society least likely to sustain themselves or succeed, are
rewarded with goods and services paid for by the confiscated wealth of a
diminishing number of producers.

In message
,
harry writes
On Sep 15, 11:49Â*pm, The Natural Philosopher
wrote:
Dave Plowman (News) wrote:
In article ,
Â* Â*tony sayer wrote:
I don't think that any of them go down that low in fact no audio
equipment I know of does, they tend to filter off below 20 Hz just
calling it wasted audio...

Except the equipment to measure turntable rumble?

There is no problem in the electronics: its the transducer that is the
problem

Not sure where Â*standard microphone capsule stops..

--
Ineptocracy

(in-ep-toc-ra-cy) €“ a system of government where the least capable to
lead are elected by the least capable of producing, and where the
members of society least likely to sustain themselves or succeed, are
rewarded with goods and services paid for by the confiscated wealth of a
diminishing number of producers.

So if it can' tbe measured then no-one knows thatit actually exists?
Sounds like urban myth to me. Invented to suit the NYMBYs?

Of course it can be measured, it just requires special equipment fit for
purpose, not off the shelf standard audio equipment


--
geoff

In article ,
The Natural Philosopher wrote:
There is no problem in the electronics: its the transducer that is the
problem

Not sure where standard microphone capsule stops..

Can't see there being a problem there - moving things slowly is usually
easier than fast. You'd likely need an omni type - directional ones use
cancellation to give their DP which will be frequeciy dependant. But many
decent ones will include some form of high pass filter to remove things
below the audio band.

--
*'Progress' and 'Change' are not synonyms.

Dave Plowman London SW
To e-mail, change noise into sound.

On 16/09/2012 07:39, harry wrote:
On Sep 15, 11:49 pm, The Natural Philosopher
wrote:
Dave Plowman (News) wrote:
In article ,
tony sayer wrote:
I don't think that any of them go down that low in fact no audio
equipment I know of does, they tend to filter off below 20 Hz just
calling it wasted audio...

Except the equipment to measure turntable rumble?

There is no problem in the electronics: its the transducer that is the
problem

Not sure where standard microphone capsule stops..

--
Ineptocracy

(in-ep-toc’-ra-cy) – a system of government where the least capable to
lead are elected by the least capable of producing, and where the
members of society least likely to sustain themselves or succeed, are
rewarded with goods and services paid for by the confiscated wealth of a
diminishing number of producers.

So if it can' tbe measured then no-one knows thatit actually exists?
Sounds like urban myth to me. Invented to suit the NYMBYs?


Having been directly involved in a lengthy battle to prevent a
140ft-tall turbine from being erected a few hundred metres from our
house & neighbours.....

....it seems that there's a whole industry of 'consultants' who are
employed to play down the effect of these turbines and force through
planning decisions...

Sound monitoring studies ignore completely the infrasound, fudge the
issue with computer-based models that are full of approximations & etc -
and are (as you'd imagine) heavily biased towards the 'Sure - you'll
hardly notice it at all' school of thought.

The same infrasound effects are used as a weapon by various militaries
and in seaborne defence against pirate attacks. Perhaps Harry would like
to stand in front of one of these devices, and then tell us that the
effects ( physical pain, breathing difficulty, vertigo, nausea,
disorientation, or other systemic discomfort - from Wiki) are imaginary?

Difference is, that although the effects from such a weapon are
short-term and intense, it's equally unpleasant to suffer similar
effects 24/7 - from an operating wind-turbine.

Luckily, in our case, the planning case went to Appeal and the original
permission was rejected... (www.ceramicxwindfarmsucks.com) - though, in
the end, that was thanks to the bats, rather than any consideration for
the humans living close by!

Adrian

On Sat, 15 Sep 2012 23:49:31 +0100, The Natural Philosopher wrote:

There is no problem in the electronics: its the transducer that is the
problem

Not sure where standard microphone capsule stops..

The DPA 4003 is flat 10Hz though that is more of the exception rather
than the rule. The rule would be flat down to nearly 20Hz for decent
microphones. If you can judge "decent" by price tag then think £1000 or
higher. Not a 5p electret capsule from maplin...

A these low frequencies it'll have to be a pressure operated microphone,
which are inherentally omni. Such low frequencies won't generate enough
signal from a pressure gradient microphone.

But of course the problem with infrasound is not so much it's
transmission through air as "sound" but through the ground or building
structure as a "vibration".

--
Cheers
Dave.

On 15/09/2012 23:36, wrote:
On 15 Sep,
Martin Brown wrote:

I don't normally find them obtrusive but the ones they have just put up
in front of the North York Moors near Middlesbrough look a right mess.

They're my local ones (Between Hilton and Seamer). They're quite attractive.
I pass them about 10 times each week.

They only look really bad when you are travelling southbound on the A19.

Close to I think they do look OK. But it is an act of gross vandalism to
put them in front of the edge of a national park like that.

--
Regards,
Martin Brown

The Natural Philosopher wrote:

Chris J Dixon wrote:
The Natural Philosopher wrote:

Not sure where standard microphone capsule stops..

http://www.bksv.com/Products/handheld-instruments/sound-level-meters/sound-level-meters/type-2270.aspx?sortOrder=

3 Hz-20 kHz broadband linear frequency range


3 Hz-20 kHz broadband linear frequency range
16.6 - 140 dB *A-weighted* dynamic range with supplied microphone Type 4189

"A" weighting is USELESS for infrasound.

You are quite right, I missed that.

However, it looks like they produce a mike specifically for
infrasound measurement:

http://www.bksv.com/Products/transdu...spx?sortOrder=

4193 - ½-inch infrasound microphone, 0.07 Hz to 20 kHz

It isn't clear which meter it can be used with.

Chris
--
Chris J Dixon Nottingham UK


Have dancing shoes, will ceilidh.

On Sep 16, 1:34*pm, "Dave Plowman (News)"
wrote:
Can't see there being a problem there - moving things slowly is usually
easier than fast. You'd likely need an omni type - directional ones use
cancellation to give their DP which will be frequeciy dependant. But many
decent ones will include some form of high pass filter to remove things
below the audio band.

Unfortunately there is nearly always a lot below the "audio" band.
Just closing a door creates very high levels of infrasound, especially
if the room is well sealed. In vehicles the effects can be extreme.
I once measured sound pressure levels of around 140dB SPL at
frequencies of around 10Hz with a B&K sound level meter in "flat
response" mode in a "luxury" car travelling at high speed (with the
windows closed). I think the A-weighted reading was around 70dBSPL.

Although such infrasound levels are barely audible, they exceed the
dynamic range of most microphones, especially the cheaper electret
types. To overcome this, the manufacturers of omni-directional
electrets laser-drill tiny holes in the diaphragm to provide a
controlled bypass leak which gives a high-pass frequency response
curve. Without this, they would sound terrible under ordinary
conditions as there would be frequent mechanical clipping.

Such microphones are used in many of the low-cost sound level meters
on the market. This means that even if the A-weighting is disabled
(which is seldom possible) they are still incapable of accurately
measuring infrasound. There is certainly lots of scope for accidental
or deliberate mis-reporting.

John