Hi all,

I've been recording lectures for my classes using the Zoom H2 (
http://www.zoom.co.jp/english/products/h2/) portable audio recorder. I
normally sit near the front (no more than 5 or 6 m away from the professor)
and therefore tend to catch a lot of background noise, as well as noise fro=
m
other students.

1. At this distance, the high gain mode is more than enough to capture what
the professor is saying, however if someone sitting near the recorder cough=
s
or sneezes or flips a page or smashes their face against their desk, I get
high amplitude clicks in the recording. Such noises are far louder than the
sound from the professor. Because of this, I find it hard to "normalize" th=
e
recording using Audacity since the maximum amplitude wont be adjusted to
more than 0 db.

How would i clip off these loud spikes? In Audacity, they're clearly visibl=
e
as tall spikes, compared to the rest of the recording.

2. Audacity also has a really nice noise removal function. You select a
section of audio (as a sample) that is "noise", and it filters that noise
out from the entire recording. For lectures, the beginning and end of the
lectures are noisy, as everyone settles down. The quietest sections can be
found in the middle of the lectures. However, during that time, I find it
hard to find a gap where it's *only* noise and the professor isn't talking
(since he is almost always speaking). Any ideas as to how to remove this
noise?

3. I have a question about decibels. I understand that when measuring volum=
e
or sound intensity, 0 dB is the level at which sound is barely audible for
the average human. So, any sound that is louder will use that barely audibl=
y
sound as a reference on the decibel scale.

3.1. However, the normalizing function says it will stretch the maximum
amplitude to 0 dB. What does this mean? What is the reference?

3.2. My recorder has a sound intensity scale (I think) that is showing
values from -48 dB all the way up to 0 dB on the high end. You can see the
bar moving higher if you speak louder. I don't understand this scale.
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