Angelo Campanella
2009-09-12 04:24:53 UTC
Dear All:
I just cam back from investigating a situation where a lady was
complaining of sounds that did not cease, typically faint high frequency
sounds within her house and at its outside perimeter. Tinnitus aside
(arbitrary whether she has tinnitus; if so, it's incipient and certainly not
outstanding), I spent an hour or two in nice late summer calm weather
looking for such sounds with a 1/2" mic and a spectrum analyzer that
detected up to about 50 kHz. Besides the usual Ohio fall crickets, etc.
there was a persistent 5.8 kHz emission and an occasional 16 kHz emission on
and off. These were detectable all about the yard and stronger within some
old mature trees.
She said she heard them ( better than I ever did), but they were not her
main complaint.. The 5800 Hz signal was at a level varying from 40 to over
50 dB. I'm not sure of the normal human threshold for the frequency. But I
do know that noise damage to cochlear nerves destroys this frequency range
first, so I did not hear it. The lady's hearing test result had been that
she has good high frequency hearing.
A side issue, perhaps more impotent to us than her travail, is just
exactly what insect is this? A quick look at Wikipedia says that there re
50,000 types of insects - and - counting. So I don't thinks all these guys
have been documented (undocumented insects! what next!) . Also found an
abstract about an investigation of mating spiders that emit (beating of the
male's wings in that case).
================
P. Trematerraa and G. Pavanb
a Dipartimento di Scienze Animali, Vegetali e dell' Ambiente, University of
Molise, Via Cavour 50, I-86100, Campobasso, Italy
b Centro Interdisciplinare di Bioacustica, University of Pavia, Via
Taramelli 24, I-27100, Pavia, Italy
Received 1 August 1994. Available online 21 February 2000.
Ultrasonic emission in the mating behaviour of three species of Lepidoptera:
Pyralidae, Ephestia cautella (Walk.), E. kuehniella Z. and Plodia
interpunctella (Hb.), is reported. Sounds consist of quite regular sequences
of ultrasonic pulses reaching a frequency of up to 80 kHz, emitted by
wing-fanning males during courtship behaviour. Preliminary results on the
role of the emission in pair-forming is discussed.
Author Keywords: Phiticinae; courtship behaviour; ultrasonic communication
=============================================
This is way out of the range I detectd.
But there was a second sound that I detected around 15 kHz; This was strong
for short whiles, then nil. (mating?). Found it in a few locations about the
property, usually in bushy vegitation. I was able to direction-find
("localize") by rotating with the microphone pointed horizontally; good
front-to back ratio. But a few such maneuvers did not get me close (no big
buildup of intensity beyond about 50 dB @ 16 kHz).
Beating of wings may be the general MO for insect ultrasound production.
Gnats almost certainly are in this category of high frequency sound
emitters.
I didn't solve her problem, just assured her that nothing unusual
technically was going on in her environment..
But the 6 and 15 kHz emissions are real.
I looked at the 1/2" mic output up to about 50 kHz, and saw nothing but a
monotonically demising background noise, perhaps some activity around 30
kHz..
(I have checked the sensitivity of 1/2" mics up to about 50 kHz. At 20 kHz,
there is considerable aperture gain so that on-axis sensitivity is good
there. The aperture gain continues to rise with frequency, but around 40
kHz, the grid causes shadowing and diffraction effects. It takes a lot to
explain and there is a lot to understand. There is a hump at 45 kHz and a
hump at 50 kHz, then much less (work remains to be done). There is the
matter of higher vibration modes of the diaphragm sitting on a chamber of
air.
Anyway, back to Ohio country insect noise in September, My best guess is
that there are critters in the old vegetation having their late summer
soiree's, and I sure wish I could know who they are.
Angelo Campanella
I just cam back from investigating a situation where a lady was
complaining of sounds that did not cease, typically faint high frequency
sounds within her house and at its outside perimeter. Tinnitus aside
(arbitrary whether she has tinnitus; if so, it's incipient and certainly not
outstanding), I spent an hour or two in nice late summer calm weather
looking for such sounds with a 1/2" mic and a spectrum analyzer that
detected up to about 50 kHz. Besides the usual Ohio fall crickets, etc.
there was a persistent 5.8 kHz emission and an occasional 16 kHz emission on
and off. These were detectable all about the yard and stronger within some
old mature trees.
She said she heard them ( better than I ever did), but they were not her
main complaint.. The 5800 Hz signal was at a level varying from 40 to over
50 dB. I'm not sure of the normal human threshold for the frequency. But I
do know that noise damage to cochlear nerves destroys this frequency range
first, so I did not hear it. The lady's hearing test result had been that
she has good high frequency hearing.
A side issue, perhaps more impotent to us than her travail, is just
exactly what insect is this? A quick look at Wikipedia says that there re
50,000 types of insects - and - counting. So I don't thinks all these guys
have been documented (undocumented insects! what next!) . Also found an
abstract about an investigation of mating spiders that emit (beating of the
male's wings in that case).
================
P. Trematerraa and G. Pavanb
a Dipartimento di Scienze Animali, Vegetali e dell' Ambiente, University of
Molise, Via Cavour 50, I-86100, Campobasso, Italy
b Centro Interdisciplinare di Bioacustica, University of Pavia, Via
Taramelli 24, I-27100, Pavia, Italy
Received 1 August 1994. Available online 21 February 2000.
Ultrasonic emission in the mating behaviour of three species of Lepidoptera:
Pyralidae, Ephestia cautella (Walk.), E. kuehniella Z. and Plodia
interpunctella (Hb.), is reported. Sounds consist of quite regular sequences
of ultrasonic pulses reaching a frequency of up to 80 kHz, emitted by
wing-fanning males during courtship behaviour. Preliminary results on the
role of the emission in pair-forming is discussed.
Author Keywords: Phiticinae; courtship behaviour; ultrasonic communication
=============================================
This is way out of the range I detectd.
But there was a second sound that I detected around 15 kHz; This was strong
for short whiles, then nil. (mating?). Found it in a few locations about the
property, usually in bushy vegitation. I was able to direction-find
("localize") by rotating with the microphone pointed horizontally; good
front-to back ratio. But a few such maneuvers did not get me close (no big
buildup of intensity beyond about 50 dB @ 16 kHz).
Beating of wings may be the general MO for insect ultrasound production.
Gnats almost certainly are in this category of high frequency sound
emitters.
I didn't solve her problem, just assured her that nothing unusual
technically was going on in her environment..
But the 6 and 15 kHz emissions are real.
I looked at the 1/2" mic output up to about 50 kHz, and saw nothing but a
monotonically demising background noise, perhaps some activity around 30
kHz..
(I have checked the sensitivity of 1/2" mics up to about 50 kHz. At 20 kHz,
there is considerable aperture gain so that on-axis sensitivity is good
there. The aperture gain continues to rise with frequency, but around 40
kHz, the grid causes shadowing and diffraction effects. It takes a lot to
explain and there is a lot to understand. There is a hump at 45 kHz and a
hump at 50 kHz, then much less (work remains to be done). There is the
matter of higher vibration modes of the diaphragm sitting on a chamber of
air.
Anyway, back to Ohio country insect noise in September, My best guess is
that there are critters in the old vegetation having their late summer
soiree's, and I sure wish I could know who they are.
Angelo Campanella