An Infrasound Query for Audio Buffs

[Night Walker]

Can infrasound - sound with frequencies below the human audible range - be recorded on standard audio recording devices (tape recorder, MP3 recorder)?

If so, can those sounds 1) be tweaked into the human audible range and/or 2) be displayed graphically?

If not, what specific equipment is needed to record, playback, and display infrasound?

[Dion]

Good question Night Walker

I know EVP’s can be picked up using general purpose recording equipment.

EVP stands for Electronic Voice Phenomena, and is used to pick up ghostly sounds and voices. I am sure that EVP is not audible to the human ear.

Here is a link to Tracey’s EVP’s viewtopic.php?f=54&t=1816

Going off your post Night Walker I Sense there is something you wish to record that is out of your general hearing capacity? Am I right? Or is it that your just curious?

[Night Walker]

Mere studious curiosity at this point however I do like to be prepared whilst in the field.

EVP would seem like a different phenomenon to infrasound in my understanding. EVPs, while not heard in situ, are clearly (or not so clearly) audible when played back. If infrasound is recorded on tape it still would not be heard with conventional playback.

[Mike Williams]

Can infrasound - sound with frequencies below the human audible range - be recorded on standard audio recording devices (tape recorder, MP3 recorder)?

From what little I know..possibly not ..since you need a large resonant cavity to pick up and amplify the pressure waves first..and convert them too sound.
I made a subsonic microphone years ago from a 2 tubes of pvc.
The first tube was sealed with rubber at one end..
This was resting in the middle of another tube with a diameter the size of a bowling ball.
The inner tube picked up vibrations, these were carried up from the the rubber surface and transmitted up a wire to the surface of the larger tube, which had the guts of a stylus stripped out, the vibration/infra?/subsonic pressure waves..then became sound .

f so, can those sounds 1) be tweaked into the human audible range

Yes

be displayed graphically?

if you had the $$$, sure

[topender]

Speaking of playing around with infra sound, ive asked a fella from our Electronics dept to knocked me up a device that emits sound at 18hz, ...NO im not sure what im going to do with it or its effects, but im going to find out, from what i read lots of things occur at 18hz

[Night Walker]

Mike & topender - would either of you be able to supply schematics for your respective contraptions? I'd love to conduct some infrasound experiments in the hills around Kilcoy...

[Mike Williams]

Having pm problems...doesnt appear sent..so I hope you received the subsonic details..


Mike

[topender]

I got sent schematics last year, quite complicated things they are too...if it was a human body.no probs...electrics no way, i will try to attach to a PM

[Strange2]

The biggest problem you will face trying to build your own detector is that Infrasound wavelengths are so long that they can be detected only by sensors that take up a large area. So, if you are series about building your own detector you will most likely need a trailer for your field research.

eg: If you wanted to detect a frequency of 3 Hz you would need a very large 725 gallon water tank as a resonator.

There are plenty of laboratory condenser microphones that routinely respond far below 20 Hz. The Bruel & Kjaer capsule have lower limiting frequencies specifed down to 1-3 Hz (-3 dB) and there specialized microphon systems that have responses FAR below that. One example being the B&K 4147, which is specified as being -3 dB at 0.001 Hz (that's 1 cycle every 15 minutes). Even some of the cheap electret condenser mics (cheap as in a couple of dollars) have reasonable responses below 20 Hz.

And you would need an Analog to Digital Card for Seismic and Other Low Frequency Data Recording.

A seismometer A/D board or something similar...
http://www.seismicnet.com/serialatod.html

Cheers

[Night Walker]

Thank you all for the replies. However, it would seem that the recording of infrasound is somewhat outside my means at the moment. I am a low-tech researcher out of necessity.

What about creating deep soundwaves?

I read somewhere that kids used to get a strange whining noise by rubbing a stretched wire between 2 tins. If upscaled to a bass guitar string stretched tight between 2 metal barrels would that work?

Any other ideas?

[Shazzoir]

Night Walker, how about getting hold of an old glass Cider jug, you know, the ones the Jug Band guys used to use? You blow across the neck, and it creates a quite haunting, odd, muted booming sort of note. Maybe this might serve to get Yowies' attention?

Kind regards,
Shazz

[Muppets]

Night Walker, how about getting hold of an old glass Cider jug, you know, the ones the Jug Band guys used to use? You blow across the neck, and it creates a quite haunting, odd, muted booming sort of note. Maybe this might serve to get Yowies' attention?

Kind regards,
Shazz

Sure, if the yowies are a hillbilly band.
(plays theme from Deliverance on banjo)

[Tracey]

This was written by Danny from Leinster Paranormal in Ireland. It may help you.

Noise and sound are acoustic waves carried on oscillating particles in the air. The frequency of sound (Hz) is defined by the number of oscillations per second and how we perceive noise is partly dependant on what the frequency is. High frequency noise has more oscillations per second whereas low frequency noise has fewer.

Infrasound (sound that is not audible)

The frequency range of infrasound is usually defined as below 20Hz. Audible noise is usually defined as between 20-20,000 Hz. Although sound is audible below 20Hz, tones are lost between 16 and 18Hz resulting in many people not being able to hear the sound.

Dr Geoff Leventhall, expert consultant in Noise Vibration and Acoustics and author of the UK DEFRA (peer reviewed) report on infrasound, states: “I can state quite categorically that there is no significant infrasound from current designs of wind turbines. To say that there is an infrasound problem is one of the hares which objectors to wind farms like to run.”

Low frequency noise

Low frequency noise stretches across the frequency band from approximate 10 to 200 Hz, thereby being included within both the infrasonic and audible definitions.

At the beginning of 2004, a newspaper reported a claim that ‘low frequency noise’ or ‘infrasound’ could be produced by wind turbines, and that this was possibly a cause of sleep interruption and headaches.

First of all it should be understood that both human made and natural sound sources produce elements of low frequency noise or infrasound. It should also be understood that low frequency noise has been around through our evolution as human beings without hazard – there are even low frequency fluctuations within our bodies associated with blood flow known to have audible effects.

A document ‘Low frequency noise and vibrations at a modern wind farm’ (ETSU W/13/00392/REP), commissioned by the DTI in 1997, comprehensively assessed the vibrations from wind turbines. It concluded that:
• vibration levels attenuated rapidly with distance
• there was no clear increase in vibration with wind speed
• 100 metres away from the turbine (i.e. on the wind farm site itself), levels were 10 times lower than the requirements for modern laboratories.

Overall, modern wind turbines emit negligible amounts of low frequency noise.

I have heard anti-wind farm campaigners claim that the noise from a wind turbine gets louder the further away you get. This is not technically possible according to acousticians but the human ear does hear different noise frequencies for different distances. This is due to the ability of for example air, ground or barriers such as windows to reduce perceived sound being reduced at lower frequencies. Lower frequency noise is therefore often heard over a longer distance. Try an experiment by listening to the noise next to an open window and then closing it and walking a few feet away. You will probably be able to still hear the lower frequency noises such as traffic (albeit fainter) but not the higher frequency noises.

For more information about how people perceive noise from wind farms take a look at my post is the noise all in your head? - wind turbine noise, physcology and world perspective

http://www.ecofriendlymag.com/sustainab ... ncy-noise/

[Tracey]

As we know EVP stands for Electronic Voice Phenomena.

It is generally agreed that evp is not the same as ethereal voices heard with the human ear. Many ghost groups say it isnt the same and I can see that from the name. It mean electronic phenomena .

But........I disagree that they are not the same thing. Reason being is that my group and I have heard ghost voices on investigations that have been picked up by digital voice recorders also. Many time 4 out of 7 of us may hear the faint words being spoken around us and others wont. I think the loudness of the evp has to do with the energy a spirit has drawn. I remember one time in a courthouse, 4 of us members were left on the investigation and were about to leave. It was about 3.30am and the place just came alive with raps, scratching, pops, door handles moving and then suddenly the 4 of us heard the distinct voices of a couple of men talking at the same time, a then a woman saying "oooooh!". We all looked at each other and we all heard the same thing. They were most definitely voices of the dead as we were locked in a large stone courthouse . We heard the voices come from around us but seemed to be like it was passing through something that made it quieter. It wasnt coming from outside, you could hear it next to us. Unfortunately, we never had our recorder going at this time. That was a real shame.

Here is an example of a sound heard audibly and then picked up on a sony digital recorder I was carrying. I had another investigator next to me. All was quiet. It was Maitland Gaol. There were 4 of us on a investigation . The other two girls were down the other end of the cell block setting up emf meters and a recorder. I distincly heard this humming with my ears that seemed to come from right behind me. I asked the male investigator Joe, next to me to see if he heard it but he didnt. This humming had been heard by the other girls on the way to this cell block outside earlier on and they remarked on it but I hadnt heard it.

In the first file I have amped up the section where the humming is and you have to listen for it.
The second file is the section where the humming is. It is actuall a little tune.

http://Tracey.fileave.com/girlhummingsong.mp3


Here is the extract

http://Tracey.fileave.com/girlhummingsong.wav

So......this is an evp and sounds to me to be a female child humming. We have since done some more experiments with this and captured her again on other investigations.

Its an evp but I also heard it. Why did I hear it?.......I dont know. The other investigator didnt hear it. Did I pick up a lower frequency at the time? It does happen.
You have to call this an evp because it was taken on a recorder and it is the voice of a ghost but it was heard by myself also. I have had people say that it isnt an evp because I heard it but I dont know how anyone can say that if it was picked up on an electronic device.


I use Cool Edit Pro 2 as my evp software. I try not to do to much to them except amp them and remove hiss slightly if I have to.

[Night Walker]

A cider jug may be alright. Does it project it's sound well?

I found that I can get decent projection when I slap my guitar strings instead of strumming - rythmic percussion combined with a bell-like tone when the strings are D-modal tuned. Not very deep but some interesting tones.

I also have a harmonica and drums.

Anyone up for a midnight tribal jam in Yowie territory?

[Shazzoir]

If nothing else, a curious Yowie would probably turn up just to find out what the racket was!

http://www.jugband.org/

kind regards,
Shazz

[Night Walker]

If not it would still be a hell of a lot of fun.

[Strange2]

Has anybody in Au tried feild testing sounds from any of 13 species of large apes?

Just Curious