noise-free audio recordings

[Jan Edwards]

I'm wondering if anyone can help with a problem that we are having.

We are recording young children (3 to 5 year olds) onto audiotape in order
to do acoustic analyses (spectral moments analysis and formant tracking).
We need recordings with a very good signal-to-noise ratio (preferably at
least 40 dB) for our purposes.

Some built-in limitations:
1.  We are recording children at several different sites in a "quiet"
classroom -- we can't use a soundproof booth since the kids are not coming
to us.  Therefore, we always have some ambient noise.

2.  We need to use a laptop computer since we are going to several
different sites.  The sound chips in the laptops are not of the highest
quality.

3.  Because we are recording such young children, we need to use a
head-mounted microphone to maintain a fairly standard mouth-to-microphone
distance.  This limits our choice of microphone options.

We have tried two different procedures:
1.  Recording directly onto the computer.  This method works great in our
laboratory with a high-quality sound board.  It doesn't work with the
laptop -- too much noise inherent in the poor-quality sound chips that are
built into the laptop.

2.  Recording with a Shure head-mounted microphone, a preamp (made by our
technician), and a SONY portable digital audio tape recorder.  These
recordings also have been noisy.

Has anyone else had better luck making recordings under similar conditions?
Any suggestions would be greatly appreciated.

Jan Edwards