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)

You can also use the excellent alsa-capabilities script.

Invoke the above script with bash alsa-capabilities which results in the output below.


root@audio:~# bash alsa-capabilities

 0) USB Audio Class Digital alsa audio output interface `hw:0,0'

 - device name       = Cambridge Audio USB Audio 2.0

 - interface name    = USB Audio

 - usb audio class   = (n/a)

 - character device  = /dev/snd/pcmC0D0p

 - encoding formats  = S32_LE

 - monitor file      = /proc/asound/card0/pcm0p/sub0/hw_params

 - stream file       = /proc/asound/card0/stream0



 1) USB Audio Class Digital alsa audio output interface `hw:1,0'

 - device name       = D10

 - interface name    = USB Audio

 - usb audio class   = (n/a)

 - character device  = /dev/snd/pcmC1D0p

 - encoding formats  = S32_LE, SPECIAL, DSD_U32_BE

 - monitor file      = /proc/asound/card1/pcm0p/sub0/hw_params

 - stream file       = /proc/asound/card1/stream0

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

#

Test and measurement: Audio testing scripts for Linux

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