Hi Michael--
There are a number of factors that could complicate your objectives.
With the sketchy info you provide, its hard to know what you're
likely to encounter.
For starters, if the >20K Hz sounds are robust and you can get them
close to your mic(s) that might allow you to use a lesser expensive
mic. If not, you might need a very good mic to get useable material.
As David suggests, your computer's dsp/audio card might handle the Hi
Hz content or might not. See what the specs are on your gear. You
might elect to buy a mic that has promise from a reputable pro audio
dealer that will allow you to return it and try another if it doesn't
work.
As for the sonogram, there are many programs that do this. Are you
after a particular graphic look? Do you want a still or moving
sonogram? What computer platform are you on? Rob D.
= = =
At 10:45 PM +0000 11/4/10, michaelcroix wrote:
>
>
>Thanks for the reply David. However, I don't think you understand my needs.
>
>I don't need the ultrasonic frequencies to be audible. I just need
>to record ultrasonic sounds between 20kHz and 50kHz and display them
>on a graph showing frequency and decibel levels. I am doing this in
>the lab so I thought there may be a USB microphone/computer software
>program I could use.
>
>--- In
><naturerecordists%40yahoogroups.com>
>"Avocet" <> wrote:
>>
>> > I need an inexpensive way to record and display
>> > (decibel v frequency) ultrasonic frequencies between 20kHz and
>> > 50kHz.
>>
>> Michael,
>>
>> Inexpensive, no. Any peripherals recording digitally at 44.1 or 48 cut
>> off at below half of those frequencies to avoid aliasing. Een 96Ks/s
>> sample rate is too slow. I do bat conservation work which involves
>> frequenies up to 110KHz. There are three methods of doing this with a
>> bat detector which makes bat frequencies audible.
>> 1) heterodyne which shifts down all frequencies by a given amount, say
>> 45KHz lower, but this only covers a range of about 8KHz.
>> 2) frequency division which divides the frequency by (typically) 10
>> 3) time expansion which records a second or two and then plays it back
>> at 1/8 or 1/10 or 1/16 speed. These have three zeroes on the price
>> tag.
>>
>> You can get PCMCIA cards which digitise ultrasound but they also have
>> three zeroes. See if you can find some local bat enthusiasts who may
>> be able to help.
>>
>> Alternatively you can simulate the sounds by generating similar sounds
>> at audible frequencies and displaying them using Audacity or another
>> sound editing program as power spectrums and audiograms, and alter the
>> scaling on the displays.
>>
>> David
>>
> > David Brinicombe
>
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