In a message to All  Kushal Chakrabarti wrote:
 KC> Help!  How do I change my Hayes compatible modem to run silently...
Get into terminal mode and type the following:
ATM0&W0
That turns off the speaker and saves it in NVRAM for future use. In order to 
reverse it type:
ATM1&W0
--- QuickBBS 2.80 (Zeta-1.9A)
---------------