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Test and measurement: Audio testing scripts for Linux



Audio testing scripts for Linux (all scripts require 'sox' and 'alsa*' - On Debian or Pi - apt install sox)
*alsa is usually installed by default.
Along with Windows software, I often use Linux for audio testing.
I have written a few basic scripts to help with this.
To find the name of your audio interface - aplay -l (playback) and arecord -l (record)
The following script will generate a sine tone using sox:

#!/bin/bash
#
# edit to change bits (usually not required)
#
bits="24"
# should make this a command line parameter
playback_dev="hw:1,0"
#
if [ $# -ne 4 ]; then
echo 1>&2 "Usage: $0 Frequency(Hz) Duration(s) Sample Rate(Hz) Level(dB)"
echo "e.g. $0 1000 10 96000 -3 = 1kHz tone for 10s 96k sample rate at -3dB"
exit 3
fi
#
frequency=${1}
duration=${2}
sample_rate=${3}
level=${4}
#
echo "Playing a ${1}Hz / ${3}Hz tone at ${4}dB for ${2} seconds..."
#
AUDIODEV=$playback_dev play -r $sample_rate -n -b $bits -c 2 synth $duration sin $frequency vol ${level}dB > /dev/null 2>&1
#
#


The following script can be used to set input levels.
It requires 'parallel' (on Debian or Pi - apt install parallel)

#!/bin/bash
#
if [ $# -ne 2 ]; then
echo 1>&2 ""
echo 1>&2 "Usage: $0 Sample Rate(Hz) Level(dB)"
echo "e.g. $0 96000 -3 = 96k sample rate at -3dB"
echo 1>&2 ""
exit 3
fi
#
sample_rate=${1}
level=${2}
duration=2
datafile=/tmp/$0_output.txt
message="Set levels to ${level}dB: (wait $duration seconds for levels to appear) [ hit CTRL+C to stop ]"
rm -f $datafile
clear
echo $message
#
for i in {1..50}
do
parallel ::: "AUDIODEV=hw:3,0 play -r $sample_rate -n -b 24 -c 2 synth $duration sin 1000 vol ${level}dB > /dev/null 2>&1" "sox -b 24 -r $sample_rate -c 2 -t alsa hw:2,0 ${i}.wav trim 0 $duration > /dev/null 2>&1"
amplitude=$(sox ${i}.wav -n stats 2>&1 | grep "Pk lev dB")
echo $amplitude > $datafile
rm -f ${i}.wav
clear
echo ${message} "loop" $i
cat $datafile
done
echo "Done"
rm -f $datafile

Note: This is presented as a bash script to maintain syntax highlighting - but the commands below are intended to be used standalone.

#!/bin/bash
#
# some examples to play and record audio using arecord and sox
# all examples process 24 or 32 bits of audio at 96khz
# aplay -l will list playback devices
# arecord -l will list capture devices
#
#
# arecord - capture 60 seconds of 2 channel audio from hw:2,0 and write it to tmpwav.wav
#
arecord -D hw:2,0 -c 2 -r 96000 -fS24_3LE -d 60 tmpwav.wav
#
# sox - capture 60 seconds of 2 channel audio from hw:2,0 and write it to tmpwav2.wav
#
sox -b 24 -r 96000 -c 2 -t alsa hw:2,0 tmpwav2.wav trim 0 60
#
# generate a tone using play (part of sox)
# generate a sinewave - this will generate a 2 channel 1khz sinewave at -9dB
# of 100 seconds duration on playback hardware device 3,0 using a sample rate of 96khz
#
AUDIODEV=hw:3,0 play -r 96000 -n -b 24 -c 2 synth 100 sin 1000 vol -9dB
#
# create a file with the above instead of generating a tone
#
sox -b 32 -r 96000 -c 2 -n soundfile.wav synth 100 sine 1000 vol -9dB
#
# play a .wav file with aplay - the "-f" switch here is crucial (as with arecord above) and will vary according to your hardware
# most likely options are S24_3LE or S32_LE (there are many more - see the aplay man page for details)
#
aplay -D hw:3,0 -f S24_3LE [filename]
#
# do the same with the play (sox) utility
#
AUDIODEV=hw:3,0 play [filename]
#
# the AUDIODEV variable is not required is .asoundrc is configured correctly.
# AUDIODEV could also be set in the environment, e.g. in .bashrc e.g.
export AUDIODEV=hw:0,0
#

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