cinnamon-sound-applet: 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/bin/cinnamon-sound-applet - from package: cinnamon-control-center

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

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