sox: 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 CentOS possible default full paths are:

/usr/bin/sox - from package: sox

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/sox - from package: sox

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

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