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Old August 20th, 2007, 08:47 PM   #1
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High Frequency Mic and "Sound Shifter"

One of my favourite wildlife targets at the moment is the Tui (Parson Bird) which is coming up for the mating season any time now. It has been written (and I have observed) that much (80% or thereabouts) of this birds song is seriously too high for human hearing to catch.

Does anyone know where/ what sort of super high frequency mic's are available and a matching "frequency shifter" to get the high notes down to human hearing range? I want to get it set up as my "second channel" sound I/P.

The sound pressure levels from a group of these birds that is in hearing range is deafening, if I could catch the upper registers as well it would be mind blowing.

Thank in advance,


CS
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Old August 20th, 2007, 09:44 PM   #2
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Take a look at this website.
I haven't used any of these mics.

http://www.avisoft.com/usg/microphones.htm
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Old August 20th, 2007, 10:24 PM   #3
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Thanks Brooks.........

Interesting stuff indeed, though the prices are a tad eye watering. Think I may have to aim just a bit lower down the food chain somehow.

Interesting that they used Sennheiiser ME64,66 & 67's for a number of their demo tracks - does anyone know just how high these mikes can go? I'd swear the leaflet that came with mine simply said 60Hz to 20K Hz or thereabouts, but it would appear they go waaay higher than that.


CS
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Old August 21st, 2007, 11:10 AM   #4
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I'm thinking they used those Senn. because they have really high output, and those bird/froggy sounds are quiet.
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Old August 25th, 2007, 06:25 AM   #5
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For some years I have recorded the ultrasonic sounds of bats, using surprisingly cheap mic capsules, like these:
http://www.knowlesacoustics.com/html...tml#modelchart
from Knowles Acoustics.

Unfortunately, they are primarily designed for mobile phone use, so you have to have some electronics experience, in order to adapt them for ultrasound recording use.

Don't forget also that you need a recorder that extends into the ultrasonic range as well - the heterodyne real time 'frequency shifting' technique I think you are referring to will only allow a crude approximation of the ultrasound. To record the actual ultrasound, and then shift it downwards in post, would need a recorder like the Korg MR1:

http://www.korg.co.uk/products/digit...mr1/dr_mr1.asp

or something similar, which allows recording at much higher sampling rates and frequencies than 'normal' audio recorders.

Bit of a specialised field - which is why the prices in the earlier link are so high, I suspect.

My next experiment will be to try and capture the actual ultrasound of bats in stereo - just to see if it might shed a bit more light on just how these extraordinary 'flying mice' navigate in the dark.

Still saving up for the equipment at the moment!!
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