audio_settings: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/lib/plainbox-providers-1/checkbox/bin/audio_settings - from package: plainbox-provider-checkbox

You may install the required package with command apt-get install {package}

Error in other languages:
audio_settings: bevel nie gevind nie
audio_settings: comandă negăsită
audio_settings: comando não encontrado
audio_settings: commande introuvable
audio_settings: command not found
audio_settings: käsku ei ole
audio_settings: không tìm thấy lệnh
audio_settings: komanda nerasta
audio_settings: Kommando nicht gefunden.
audio_settings: kommandot finns inte
audio_settings: komut yok
audio_settings: nie znaleziono polecenia
audio_settings: níor aimsíodh an t-ordú
audio_settings: no se encontró la orden
audio_settings: no s'ha trobat l'ordre
audio_settings: opdracht niet gevonden
audio_settings: parancs nem található
audio_settings: perintah tidak ditemukan
audio_settings: príkaz nenájdený
audio_settings: příkaz nenalezen
audio_settings: команда не найдена
audio_settings: командата не е открита
audio_settings: 命令找不到
audio_settings: コマンドが見つかりません