sandbox: Sound level meter implementation

[fsheikh]

Sound level meter (SLM) is a typical application for embedded system working on sound input. SLM or sound pressure meter as it is sometimes called is specified by IEC and ANSI S1.4 standards. Interestingly while there are many Matlab based implementations, upon need I could not find one in native code. I was surprised since Liquid SDR has all the building blocks available and thus an app can be rapidly built and it worked!

I hope this will be a useful application for embedded users of Liquid. At the very least it provides yet another example program for reference to Liquid users. Please check out the top of source file for references, usage and testing options for this program.

[JayKickliter]

clang's scan-build reports this minor issue on your new file:

ccc-analyzer -g -O2  -msse4.1 -Wall -fPIC -I. -Iinclude  -c -o sandbox/sound_level_meter.o sandbox/sound_level_meter.c
sandbox/sound_level_meter.c:89:39: warning: format specifies type 'size_t' (aka 'unsigned long') but the argument has type 'uint64_t'
      (aka 'unsigned long long') [-Wformat]
                            filename, samples_read);
                                      ^~~~~~~~~~~~
1 warning generated.

[fsheikh]

clang's scan-build reports this minor issue on your new file:

Thanks for having a look and pointing this out, I will fix this along with a couple other typos I have noticed.