Listener

First install libsndfile!
Then: 
make install
Then run 'setlistener' with as parameter the device to listen to. 
setlistener /dev/dsp
Then, with the left and right arrow keys, move the '|' until the word "" appears. No, don't you move the '|' to the maximum right, move it to the right until the "" just constantly appears. Then: remember the value "Current level: ".

Next step is creating the file /usr/local/etc/listener.conf Copy the example listener.conf to the location mentioned above and edit it to suit your needs.
For example: 
wav_path = /home/folkert/recordings
devname = /dev/dsp
detect_level = 800
min_duration = 1
max_duration = 300
rec_silence = 5
sample_rate = 44100
channels = 1
compression = ima-adpcm
from_pipe = 0
exec = /home/folkert/encode_sample

sample_rate

Sets the samplerate at which the samples are recorded. Be warned: only the rates supported by your soundcard can be entered here!

rec_silence

sets the number of seconds to keep on recording when no sound is detected. if during those 5 seconds sound is detected again, the timer is restarted.

min_duration

sets how many samples must be above the threshold (the 'detect_level') before recording starts. The samplerate is set to 44.1kHz so if you set min_duration to 4410, the minimum length (duration) of sound before the recording starts is: 0.1s (or: one tenth of a second).

max_duration

how long a sample may be before a new file is started

channels

sets the number of channels to record. default is 1 which is mono, 2 is stereo

compression

sets the compressionmethod. Can be: If you omit the compression-line completely, no compression is used.

from_pipe

sets wether listener is reading from a pipe fed by listenersoundpipe. listenersoundpipe lets you split a sound- device in two so that you can check 2 rooms with only one sound- card. You need to create two pipes and start 2 listener processes, each reading from one pipe.

exec

selects the script/program to execute after the sample was recorded. This first (and only) parameter for that script is the filename of the sample.

filter

lets you add one or more filters. these will be used when detecting sounds. beware: sound is written to the wav-files BEFORE the filtering is done. See the directory 'filter_lib_example' for an example on how to write a filter for listener.
safe_after_filtersets wether to save the audio-data to disk before or after the filtering. Before the filtering gives you the original sound while after gives you the sound after processing with the filter(s).
Enter 'on' or 'off'.

The final step is starting the program: 
listener
and that's it!

Thanks to Hugo Hugo for adding code that enables you to set some parameters from the commandline.

If you have any suggestions or anything else, do not hesitate to contact me at the following e-mail address:
folkert@vanheusden.com