[LAU] Realtime sound level measurement with logging

Joel Roth joelz at pobox.com
Sat May 13 02:30:42 UTC 2017

Jonathan Gazeley wrote:
> Hi folks,
> I'd like to set up sound level monitoring for my office, with periodic
> logging. I have a handheld meter but I'm really looking for a way to use a
> traditional condenser microphone and USB audio interface to measure the
> level with some kind of windowing, and log it periodically to a file (maybe
> once per minute). Is there a decent application that can monitor and log
> data in this way?
> I'm also open to the idea of just recording a WAV file over 24 hours and
> doing the analysis afterwards, with periodic readings from the file.
> Is my approach reasonable, to set up a microphone and use the gain knob to
> calibrate it against the handheld meter?
> I don't need amazing accuracy. We've just moved into a large open-plan
> office for the first time and it is very noisy (handheld meter says about
> 50dB of air handling noise measured at my desk, rising to 60dB when there is
> background talking). I want to monitor sound levels throughout the day to
> test my theory that people are more noisy in the afternoon, and to get an
> overnight control reading with the people gone and only the air handling and
> computers running.

Hi Jonathan,

I think ecasound might be able to serve your purpose. 

The way it works is your send the signal through a chain
with the -ev operator, run the engine for a while,
then use the 'cop-status' command, which provides
text output with statistics about the audio that 
was processed. 

Here's an example of a non-realtime analysis of a .wav file,
omitting some irrelevant messages.
$ ecasound -i tmh.wav -ev -o null -c

ecasound ('h' for help)>  start

[engine finishes]

ecasound ('h' for help)> cop-status

### Chain operator status (chainsetup 'untitled-chainsetup') ###
Chain "default":
        1. Volume analysis: [1] cumulative-mode 1.000, [2] result-max-multiplier 1.000
        Status info:
-- Amplitude statistics --
Pos/neg, count,(%), ch1...n
Pos    3dB: _______0 _______0
Pos    0dB: _______0 _______0
Pos -0.1dB: _______0 ______17
Pos   -3dB: _____717 ____3247
Pos   -6dB: ___26347 ___58661
Pos  -10dB: __206742 __280703
Pos  -20dB: _1177971 _1203440
Pos  -30dB: _1035427 __988797
Pos  -60dB: __754914 __677400
Pos -infdB: __214307 __211396
Neg -infdB: __107059 ___98364
Neg  -60dB: __710105 __641269
Neg  -30dB: _1030655 __963146
Neg  -20dB: _1162815 _1191367
Neg  -10dB: __218110 __291908
Neg   -6dB: ___27221 ___61362
Neg   -3dB: _____250 ____1563
Neg -0.1dB: _______0 _______0
Neg    0dB: _______0 _______0
Neg    3dB: _______0 _______0
Total.....: _6672640 _6672640
(audiofx) Peak amplitude: pos=0.99997 neg=0.96002.
(audiofx) Max gain without clipping: 1.00003.
(audiofx) -- End of statistics --


> Thanks,
> Jonathan
> -- 
> Jonathan Gazeley
> Senior Systems Administrator
> IT Services
> University of Bristol
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> Linux-audio-user at lists.linuxaudio.org
> http://lists.linuxaudio.org/listinfo/linux-audio-user

Joel Roth

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