qwavsilence: 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/qwavsilence - from package: quelcom

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

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