Post by Einstein2 on Mar 24, 2013 21:03:22 GMT -6
Questions & answers on everyday scientific phenomena
What some people reported and found out!.
Ghostly voices
Question
In 1980, my husband and I sailed from New Zealand to Hawaii and back.
Just the other day we confessed to each other that, on quiet nights in
the middle of the ocean when there was very little wind and hence very
little boat noise, we could hear voices coming from the mast. These
voices would be both male and female but you couldn't make out what
they were saying. We were both quite sober and were not under stress.
Can anyone explain this? Our mast is aluminum and the stays are made
of coiled wire.
Jenny Pollock , Nelson, New Zealand
Answers
The ghostly voices were from short-wave radio stations--possibly quite
a few of them overlapping. The mast and the rigging of a typical small
boat are just about the right size to resonate at the frequency of a
short-wave radio signal. If two items of metal are joined and there is
some corrosion between them, the junction will act as a diode and
"rectify" or demodulate the AM radio signal. This causes an
audio-frequency current to flow in the metal.
There are several mechanisms by which the audio-frequency signal could
be converted into sound waves, including causing vibration of the
rigging as the current interacts with the Earth's magnetic field.
Sam Mulholland , Bristol
With amplitude modulated (AM) radio waves, rectification is sufficient
to give an audio signal. That's how the old crystal sets worked. The
aluminum mast with an oxide layer or other corrosion could easily
cause rectification, particularly if there was contact with other
metals. Turning this electrical signal into sound waves is less easy
to explain, as the mast or rigging would need to vibrate in some way.
Many years ago I experienced this type of reception in the Antarctic
in a wooden hut that was heated by a free-standing stove with a metal
flue. It was noticed only occasionally and only with our own
transmissions--the transmitter and its aerials were fairly close. The
sound could be clearly heard coming from the flue.
David Simmons , Bottisham Cambridge
The voices the couple heard were radio waves that were being picked up
by the mast and stay arrangement. Either the mast or the hull was
acting as the speaker.
When I was a child, my family and I heard radio broadcasts at nights
through our water heater. The pipes acted as the antenna and either
the heater itself, or the small room it was in, acted as the speaker.
George Siegenthaler , Norman Oklahoma
During the Second World War the same phenomenon gave rise to many
erroneous reports of the "foreign invaders" in areas of Britain close
to short-wave transmitters. Strange voices in hedgerows at night were
reported to the police or the Home Guard. On investigation it was
found that modulated arcs on barbed-wire fences were picking up BBC
World Service transmissions.
Mike Wootton , Pattingham Staffordshire
Back in the 1930s and 1940s a super-powerful AM transmitter was
installed on an experimental basis in Texas. Local residents reported
music coming from fence wire, bathtubs and even tooth fillings.
Update:
I read certain types of filling used today still occasionally causes problems and when repaired the unexplained phenomena stops.
=================================================
What some people reported and found out!.
Ghostly voices
Question
In 1980, my husband and I sailed from New Zealand to Hawaii and back.
Just the other day we confessed to each other that, on quiet nights in
the middle of the ocean when there was very little wind and hence very
little boat noise, we could hear voices coming from the mast. These
voices would be both male and female but you couldn't make out what
they were saying. We were both quite sober and were not under stress.
Can anyone explain this? Our mast is aluminum and the stays are made
of coiled wire.
Jenny Pollock , Nelson, New Zealand
Answers
The ghostly voices were from short-wave radio stations--possibly quite
a few of them overlapping. The mast and the rigging of a typical small
boat are just about the right size to resonate at the frequency of a
short-wave radio signal. If two items of metal are joined and there is
some corrosion between them, the junction will act as a diode and
"rectify" or demodulate the AM radio signal. This causes an
audio-frequency current to flow in the metal.
There are several mechanisms by which the audio-frequency signal could
be converted into sound waves, including causing vibration of the
rigging as the current interacts with the Earth's magnetic field.
Sam Mulholland , Bristol
With amplitude modulated (AM) radio waves, rectification is sufficient
to give an audio signal. That's how the old crystal sets worked. The
aluminum mast with an oxide layer or other corrosion could easily
cause rectification, particularly if there was contact with other
metals. Turning this electrical signal into sound waves is less easy
to explain, as the mast or rigging would need to vibrate in some way.
Many years ago I experienced this type of reception in the Antarctic
in a wooden hut that was heated by a free-standing stove with a metal
flue. It was noticed only occasionally and only with our own
transmissions--the transmitter and its aerials were fairly close. The
sound could be clearly heard coming from the flue.
David Simmons , Bottisham Cambridge
The voices the couple heard were radio waves that were being picked up
by the mast and stay arrangement. Either the mast or the hull was
acting as the speaker.
When I was a child, my family and I heard radio broadcasts at nights
through our water heater. The pipes acted as the antenna and either
the heater itself, or the small room it was in, acted as the speaker.
George Siegenthaler , Norman Oklahoma
During the Second World War the same phenomenon gave rise to many
erroneous reports of the "foreign invaders" in areas of Britain close
to short-wave transmitters. Strange voices in hedgerows at night were
reported to the police or the Home Guard. On investigation it was
found that modulated arcs on barbed-wire fences were picking up BBC
World Service transmissions.
Mike Wootton , Pattingham Staffordshire
Back in the 1930s and 1940s a super-powerful AM transmitter was
installed on an experimental basis in Texas. Local residents reported
music coming from fence wire, bathtubs and even tooth fillings.
Update:
I read certain types of filling used today still occasionally causes problems and when repaired the unexplained phenomena stops.
=================================================