speaker-test: 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/speaker-test - from package: alsa-utils

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

On Debian possible default full paths are:

/usr/bin/speaker-test - from package: alsa-utils

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

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