ch_wave: command not found

Have You tried accessing the binary with the full path?

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/ch_wave - from package: speech-tools

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