Measure loudness with a USB micro on a raspberry pi

What: Measuring loudness with a simple USB microphone on a raspberry pi
Why: Create devices which are activated by a certain noise level
How: Use python and some python libraries to analyse the sound stream

Requirements

The following hardware was used for this setup:

The following os was used on the raspberry pi:

The following python version was used (preinstalled with the corresponding raspbian):

  • Python 2.7 (PyAudio was not working for me with Python3 easily)

Setup

Besides plugging the USB microphone in the corresponding USB port (such a surprise), the following things needs to be done.

Install PortAudio

Install the dependencies:

Download the corresponding version (at the time of writing this is 190600_20161030) and uncompress it:

Build PortAudio from source:

Install NumPy, PyAudio and SoundAnalyse

Code

Below is the code I used for measuring. There are some caveats with measuring the loudness:

  • There are by default some warnings when opening the stream
  • When reading the bytes from the stream, there may be an overflow exception which will kill the script. This can be avoided by the parameter exception_on_overflow = False
  • The parameters for pyaud.open may be different depending on the used microphone. The parameters can be determined by iterating over the devices and use: pyaud.get_device_info_by_index(i)