PDA

View Full Version : Household sources of ultrasonic noise



tashirosgt
2011-Dec-02, 11:53 PM
What are common sources of ultrasonic noise around a house? Is it reasonable that a light fixture would emit ultrasound?

I'm trying out a "Marksman Ultrasonic Diagnostic Tool", which is a device that picks up ultrasonic sounds and presents them as audible sound. The serious purpose of the tool is to locate leaks in pressurized systems and mechanical noise from worn parts in machinery. However, I've only tried it around the house so far. I detect some interesting noises, but it isn't clear to me that they are all caused by sounds. For example, the device picks up strong signals from two of my light fixtures. They are identical fixtures with identical compact florescent bulbs in them (the coil shaped kind). One fixture produces (according to the device) an insect like buzzing. The other produces a strong droning sound. It's plausible that these are actual sounds since they are detected strongly when the device is pointed at the fixtures and weakly when it is moved away. However, if the device is reacting to EM waves inadvertently, that could also be strongly directional.

Incandescent lamps produce a slight droning sound, but nowhere near as loud as the florescents.

The whistling of a tea kettle is surprising quiet on the device. I hear a low pitched crackling noise.

A promotional video for the device claims that you can hear your eyes blink. I actually do hear a faint scratching noise if I point the receiver (which is just a short tube) at my eye and blink. (I suppose a powerful amplifier of audible frequencies might also detect something.)

cjameshuff
2011-Dec-03, 12:51 AM
It's quite reasonable for compact fluorescent bulbs to produce ultrasound, they contain a small switching power converter to drive the tube, and the magnetics and ceramic capacitors can produce sound. The same goes for switch-mode wall warts...the small, lightweight ones without a big heavy transformer inside. LCD displays are another possibility, the CCFL backlights are quite similar to the compact fluorescent bulbs, and LED backlights use a similar but lower voltage version. Most portable electronics also has switchmode converters that can cause this.

CRT displays could produce some, for the same reason. A CRT TV might produce an ultrasonic harmonic at 31 kHz (the horizontal scan at 15.7 kHz is often audible), computer displays that work at higher refresh rates are also possible sources.

A tea kettle is probably a reasonably pure tone or set of tones. Not too surprising that there's little in the ultrasonic range.

Maybe falling water...try the shower. Or ice immediately after it's taken out of the freezer and dumped in water.

Nowhere Man
2011-Dec-03, 02:54 AM
Jingle your keyring. In amongst the audible clatter is ultrasound.

Fred

danscope
2011-Dec-03, 03:19 AM
Bats may qualify for a source.

Torsten
2011-Dec-03, 05:56 AM
I have a device that measures distances using an ultrasound transmitter/receiver and a transponder (Haglöf Vertex IV (http://www.haglofcg.com/index.php?option=com_content&view=article&id=101%3Avertex-iv&catid=40%3Adistance&Itemid=122&lang=en)). The transmitter emits a 25 kHz tone, and the transponder replies back in both ultrasound and short audible "chirps". I find that sounds from simply walking around will cause the transponder to reply, as will snapping my fingers near it.

Nowhere Man
2011-Dec-03, 01:02 PM
Unless you have an infestation, or you're an Addams, bats don't count as household objects.

Fred

HenrikOlsen
2011-Dec-03, 02:41 PM
They really do, in the world according to How I Want It To Be. I like bats.

But then I have on occasion been accused of being a distant relation to the Addamses.

Nowhere Man
2011-Dec-03, 02:50 PM
I'll let you deal with the clean-up.

On the other hand, an aluminum bat hitting a baseball probably produces ultrasonics.

Fred

Perikles
2011-Dec-03, 04:25 PM
Do you have a wood-burning stove? I think that sometimes I hear very quiet and very high frequency noises from smouldering firewood, when others can't. I can hear the supposedly ultrasonic dog whistles when other people can't. (My mother-in-law was a bat, but that's irrelevant.)

tashirosgt
2011-Dec-03, 05:24 PM
I don't have a wood burning stove.

The device I'm using isn't a scientific intstrument so it doesn't give a readout in decibels. But, subjectively speaking, the compact florescent bulbs are immensely louder than than any thing else in the house. I can hold the the detector several feet away from a wall (a 1941 era plaster wall, not simply a drywall wall) and hear a lamp with a compact florescent bulb that is on the other side of the wall. The wall seems to spread out the source of the sound.

I wonder if dogs and cats can hear the bulbs?

danscope
2011-Dec-03, 05:46 PM
My cat can hear the can-opener, but that probably doesn't count. :)

cjameshuff
2011-Dec-03, 06:10 PM
Also, plain incandescents themselves have no reason to produce ultrasound, but may ring sympathetically to some outside source, and could produce ultrasound in combination with a dimmer. Dimmers typically use PWM, and the components of the dimmer or the bulb itself could convert that to sound...I've encountered several that produced audible noise.

trinitree88
2011-Dec-03, 06:55 PM
My cat can hear the can-opener, but that probably doesn't count. :)

and bats sure can hear keys. Jingling my keys (~20) helps alert wandering polecats that a human is approaching the back of the house in twilight, saving me an unexpected fragrance, but to my surprise, a bat struck the keys in my hand last spring....must've confused it's ultrasonar signal from my keys.

danscope
2011-Dec-03, 09:37 PM
Hi, That's remarkable. I'm glad that you haven't been in the line of fire in regard to those polecats. It is not fun, and you don't want to transfer
'that' to your car or anywhere else. Dreadful,, no question.

Best regards,
Dan

Paul Wally
2011-Dec-03, 10:39 PM
Do ambulance/police sirens and car alarms extend into the ultrasound range? These sounds cause dogs to howl.

DonM435
2011-Dec-04, 04:33 AM
Also, plain incandescents themselves have no reason to produce ultrasound, but may ring sympathetically to some outside source, and could produce ultrasound in combination with a dimmer. Dimmers typically use PWM, and the components of the dimmer or the bulb itself could convert that to sound...I've encountered several that produced audible noise.

Yes, I remember installing a light dimmer in one room, and then removing it because I couldn't stand the humming and buzzing whenever it was set at less than full brightness.

TrAI
2011-Dec-04, 02:20 PM
Also, plain incandescents themselves have no reason to produce ultrasound, but may ring sympathetically to some outside source, and could produce ultrasound in combination with a dimmer. Dimmers typically use PWM, and the components of the dimmer or the bulb itself could convert that to sound...I've encountered several that produced audible noise.

It is possible that the filament of the bulb is vibrating, due to the magnetic field, though such vibration would have a low frequency, it might excite oscillations in some part that would have an ultrasonic frequency. You do not have to strike a suitable object at its resonant frequency for it to oscillate at that frequency, you know.

It is not very likely that an AC dimmer for incandescent lamps would produce much ultrasonic noise, as they generally do not alter the frequency of the AC, it only cuts off part of each half-wave.

cjameshuff
2011-Dec-04, 04:06 PM
It is possible that the filament of the bulb is vibrating, due to the magnetic field, though such vibration would have a low frequency, it might excite oscillations in some part that would have an ultrasonic frequency. You do not have to strike a suitable object at its resonant frequency for it to oscillate at that frequency, you know.

You need some content at the right frequency though, or a nonlinear element in the system to produce such content. The power company goes to some effort to keep higher frequency components out of the power grid.



It is not very likely that an AC dimmer for incandescent lamps would produce much ultrasonic noise, as they generally do not alter the frequency of the AC, it only cuts off part of each half-wave.

One type does this, and while doing so will unavoidably introduce higher frequency harmonics, it seems unlikely to account for the prominent high pitched ringing/whining noise many dimmers produce. They are almost certainly PWM, and better-designed PWM dimmers will operate in the ultrasonic range.

publiusr
2011-Dec-04, 07:59 PM
Ultrasound surgery
http://www.ted.com/talks/yoav_medan_ultrasound_surgery_healing_without_cuts .html


Good to play with infrasound too. Pick up distant waves, tornados, objects re-entering...
http://en.wikipedia.org/wiki/Infrasound

I wonder if the designs in churches, cathedrals, haunted houses play a part in supernatural beliefs. I think Persinger did work on that not related to the god helmet.

All that might be a good way to make a haunted house attraction, with an audio spotlight beaming whispers to only one person in a crowd.

tashirosgt
2011-Dec-05, 01:49 AM
I found some web pages that mention an article by David Pye in a 2007 issue of Physics World Magazine that reported measurements of ultrasound from compact. flourescent bulbs. I'm not familiar with Physics World Magazine or the article itself.